Superconducting Detectors Come of Age, or Ready to Leave the Lab

NASA Technical Reports Server (NTRS)

Moseley, Samuel H.

2008-01-01

Cryogenically cooled superconducting detectors have become essential tools for a wide range of measurement applications, ranging from quantum limited heterodyne detection in the millimeter range to direct searches for dark matter with superconducting phonon detectors operating at 20 mK. Superconducting detectors have several fundamental and practical advantages which have resulted in their rapid adoption by experimenters. Their excellent performance arises in part from reductions in noise resulting from their low operating temperatures, but unique superconducting properties provide a wide range of mechanisms for detection. For example, the steep dependence of resistance with temperature on the superconductor normal transition provides a sensitive thermometer for calorimetric and bolometric applications. Parametric changes in the properties of superconducting resonators provide a mechanism for high sensitivity detection of submillil.neter photons. From a practical point of view, the use of superconducting detectors has grown rapidly because many of these devices couple well to SQUID amplifiers, which are easily integrated with the detectors. These SQUID-based amplifiers and multiplexers have matured with the detectors; they are convenient to use, and have excellent noise performance. The first generation of fully integrated large-scale superconducting detection systems is now being deployed. Improved understanding of the operation of these detectors, combined with rapidly improving fabrication techniques, is quickly expanding the capability of these detectors. I will review the development and application of superconductor-based detectors, the ultimate limits to their performance, and consider prospects for their future applications. Continued advances promise to enable important new measurements in physics, and with appropriate advances in cryogenic infrastncturem, ay result in the use of these detectors in everyday monitoring applications.

Optimised quantum hacking of superconducting nanowire single-photon detectors

NASA Astrophysics Data System (ADS)

Tanner, Michael G.; Makarov, Vadim; Hadfield, Robert H.

2014-03-01

We explore bright-light control of superconducting nanowire single-photon detectors (SNSPDs) in the shunted configuration (a practical measure to avoid latching). In an experiment, we simulate an illumination pattern the SNSPD would receive in a typical quantum key distribution system under hacking attack. We show that it effectively blinds and controls the SNSPD. The transient blinding illumination lasts for a fraction of a microsecond and produces several deterministic fake clicks during this time. This attack does not lead to elevated timing jitter in the spoofed output pulse, and hence does not introduce significant errors. Five different SNSPD chip designs were tested. We consider possible countermeasures to this attack.

Optimised quantum hacking of superconducting nanowire single-photon detectors.

PubMed

Tanner, Michael G; Makarov, Vadim; Hadfield, Robert H

2014-03-24

We explore bright-light control of superconducting nanowire single-photon detectors (SNSPDs) in the shunted configuration (a practical measure to avoid latching). In an experiment, we simulate an illumination pattern the SNSPD would receive in a typical quantum key distribution system under hacking attack. We show that it effectively blinds and controls the SNSPD. The transient blinding illumination lasts for a fraction of a microsecond and produces several deterministic fake clicks during this time. This attack does not lead to elevated timing jitter in the spoofed output pulse, and hence does not introduce significant errors. Five different SNSPD chip designs were tested. We consider possible countermeasures to this attack.

Superlinear threshold detectors in quantum cryptography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lydersen, Lars; Maroey, Oystein; Skaar, Johannes

2011-09-15

We introduce the concept of a superlinear threshold detector, a detector that has a higher probability to detect multiple photons if it receives them simultaneously rather than at separate times. Highly superlinear threshold detectors in quantum key distribution systems allow eavesdropping the full secret key without being revealed. Here, we generalize the detector control attack, and analyze how it performs against quantum key distribution systems with moderately superlinear detectors. We quantify the superlinearity in superconducting single-photon detectors based on earlier published data, and gated avalanche photodiode detectors based on our own measurements. The analysis shows that quantum key distribution systemsmore » using detector(s) of either type can be vulnerable to eavesdropping. The avalanche photodiode detector becomes superlinear toward the end of the gate. For systems expecting substantial loss, or for systems not monitoring loss, this would allow eavesdropping using trigger pulses containing less than 120 photons per pulse. Such an attack would be virtually impossible to catch with an optical power meter at the receiver entrance.« less

Fabrication of superconducting nanowire single-photon detectors by nonlinear femtosecond optical lithography

NASA Astrophysics Data System (ADS)

Minaev, N. V.; Tarkhov, M. A.; Dudova, D. S.; Timashev, P. S.; Chichkov, B. N.; Bagratashvili, V. N.

2018-02-01

This paper describes a new approach to the fabrication of superconducting nanowire single-photon detectors from ultrathin NbN films on SiO2 substrates. The technology is based on nonlinear femtosecond optical lithography and includes direct formation of the sensitive element of the detector (the meander) through femtosecond laser exposure of the polymethyl methacrylate resist at a wavelength of 525 nm and subsequent removal of NbN using plasma-chemical etching. The nonlinear femtosecond optical lithography method allows the formation of planar structures with a spatial resolution of ~50 nm. These structures were used to fabricate single-photon superconducting detectors with quantum efficiency no worse than 8% at a wavelength of 1310 nm and dark count rate of 10 s-1 at liquid helium temperature.

Sensors and detectors based on superconducting devices. July 1988-June 1989 (Citations from the COMPENDEX data base). Report for July 1988-June 1989

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1989-07-01

This bibliography contains citations concerning gradiometers, magnetometers, and infrared detectors which use superconductors to improve sensitivity. Applications include biomagnetic measurements for medical studies, gravity-wave experiments, geomagnetism and ocean-bottom magnetic exploration, galvanometers and voltmeters, and bolometers and radiometers. Some articles refer to design considerations for cooling systems for the sensors and detectors, and fabrication techniques for SQUIDs (superconducting quantum interference devices.) (This updated bibliography contains 74 citations, all of which are new entries to the previous edition.)

Sensors and detectors based on superconducting devices. January 1970-June 1988 (Citations from the COMPENDEX data base). Report for January 1970-June 1988

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1989-07-01

This bibliography contains citations concerning gradiometers, magnetometers, and infrared detectors which use superconductors to improve sensitivity. Applications include biomagnetic measurements for medical studies, gravity-wave experiments, geomagnetism and ocean-bottom magnetic exploration, galvanometers and voltmeters, and bolometers and radiometers. Some articles refer to design considerations for cooling systems for the sensors and detectors, and fabrication techniques for SQUIDs (superconducting quantum interference devices.) (This updated bibliography contains 394 citations, none of which are new entries to the previous edition.)

Sensors and detectors based on superconducting devices. July 1982-February 1989 (Citations from the EI Engineering Meetings data base). Report for July 1982-February 1989

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1989-04-01

This bibliography contains citations from conference proceedings concerning gradiometers, magnetometers, and infrared detectors which use superconductors to improve sensitivity. Applications include biomagnetic measurements for medical studies, gravity-wave experiments, geomagnetism and ocean bottom magnetic exploration, galvanometers and voltmeters, and bolometers and radiometers. Some articles refer to design considerations for cooling systems for the sensors and detectors, and fabrication techniques for SQUIDS (superconducting quantum interference devices.) (Contains 115 citations fully indexed and including a title list.)

Sensors and detectors based on superconducting devices. January 1970-June 1988 (Citations from the Engineering Index data base). Report for January 1970-June 1988

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1988-07-01

This bibliography contains citations concerning gradiometers, magnetometers, and infrared detectors which use superconductors to improve sensitivity. Applications include biomagnetic measurements for medical studies, gravity-wave experiments, geomagnetism, and ocean-bottom magnetic exploration, galvanometers and voltmeters, and bolometers, and radiometers. Some articles refer to design considerations for cooling systems for the sensors and detectors, and fabrication techniques for squids (superconducting quantum interference devices.) (This updated bibliography contains 394 citations, 71 of which are new entries to the previous edition.)

Quantum Computers

DTIC Science & Technology

2010-03-04

and their sensitivity to charge and flux fluctuations. The first type of superconducting qubit , the charge qubit , omits the inductance . There is no...nanostructured NbN superconducting nanowire detectors have achieved high efficiency and photon number resolution16,17. One approach to a high-efficiency single...resemble classical high- speed integrated circuits and can be readily fabricated using existing technologies. The basic physics behind superconducting qubits

Three Temperature Regimes in Superconducting Photon Detectors: Quantum, Thermal and Multiple Phase-Slips as Generators of Dark Counts

PubMed Central

Murphy, Andrew; Semenov, Alexander; Korneev, Alexander; Korneeva, Yulia; Gol’tsman, Gregory; Bezryadin, Alexey

2015-01-01

We perform measurements of the switching current distributions of three w ≈ 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter of the vortex cores, so they are classified as quasi-two-dimensional (quasi-2D). We discover evidence of macroscopic quantum tunneling by observing the saturation of the standard deviation of the switching distributions at temperatures around 2 K. We analyze our results using the Kurkijärvi-Garg model and find that the escape temperature also saturates at low temperatures, confirming that at sufficiently low temperatures, macroscopic quantum tunneling is possible in quasi-2D strips and can contribute to dark counts observed in single photon detectors. At the highest temperatures the system enters a multiple phase-slip regime. In this range single phase-slips are unable to produce dark counts and the fluctuations in the switching current are reduced. PMID:25988591

Three temperature regimes in superconducting photon detectors: quantum, thermal and multiple phase-slips as generators of dark counts.

PubMed

Murphy, Andrew; Semenov, Alexander; Korneev, Alexander; Korneeva, Yulia; Gol'tsman, Gregory; Bezryadin, Alexey

2015-05-19

We perform measurements of the switching current distributions of three w ≈ 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter of the vortex cores, so they are classified as quasi-two-dimensional (quasi-2D). We discover evidence of macroscopic quantum tunneling by observing the saturation of the standard deviation of the switching distributions at temperatures around 2 K. We analyze our results using the Kurkijärvi-Garg model and find that the escape temperature also saturates at low temperatures, confirming that at sufficiently low temperatures, macroscopic quantum tunneling is possible in quasi-2D strips and can contribute to dark counts observed in single photon detectors. At the highest temperatures the system enters a multiple phase-slip regime. In this range single phase-slips are unable to produce dark counts and the fluctuations in the switching current are reduced.

Crosstalk-free operation of multielement superconducting nanowire single-photon detector array integrated with single-flux-quantum circuit in a 0.1 W Gifford-McMahon cryocooler.

PubMed

Yamashita, Taro; Miki, Shigehito; Terai, Hirotaka; Makise, Kazumasa; Wang, Zhen

2012-07-15

We demonstrate the successful operation of a multielement superconducting nanowire single-photon detector (SSPD) array integrated with a single-flux-quantum (SFQ) readout circuit in a compact 0.1 W Gifford-McMahon cryocooler. A time-resolved readout technique, where output signals from each element enter the SFQ readout circuit with finite time intervals, revealed crosstalk-free operation of the four-element SSPD array connected with the SFQ readout circuit. The timing jitter and the system detection efficiency were measured to be 50 ps and 11.4%, respectively, which were comparable to the performance of practical single-pixel SSPD systems.

A superconducting focal plane array for ultraviolet, optical, and near-infrared astrophysics.

PubMed

Mazin, Benjamin A; Bumble, Bruce; Meeker, Seth R; O'Brien, Kieran; McHugh, Sean; Langman, Eric

2012-01-16

Microwave Kinetic Inductance Detectors, or MKIDs, have proven to be a powerful cryogenic detector technology due to their sensitivity and the ease with which they can be multiplexed into large arrays. A MKID is an energy sensor based on a photon-variable superconducting inductance in a lithographed microresonator, and is capable of functioning as a photon detector across the electromagnetic spectrum as well as a particle detector. Here we describe the first successful effort to create a photon-counting, energy-resolving ultraviolet, optical, and near infrared MKID focal plane array. These new Optical Lumped Element (OLE) MKID arrays have significant advantages over semiconductor detectors like charge coupled devices (CCDs). They can count individual photons with essentially no false counts and determine the energy and arrival time of every photon with good quantum efficiency. Their physical pixel size and maximum count rate is well matched with large telescopes. These capabilities enable powerful new astrophysical instruments usable from the ground and space. MKIDs could eventually supplant semiconductor detectors for most astronomical instrumentation, and will be useful for other disciplines such as quantum optics and biological imaging.

Multispectral Superconducting Quantum Detectors

DTIC Science & Technology

1995-08-01

Noise 30 2.2.6.3 YBCO QSKIP Noise Equivalent Power 31 2.2.7 Competing LWIR Semiconductor Based Quantum Detectors 33 2.2.8 Conclusions on Operation...spectrum. Of particular interest are photodetectors operating in the midwave 3-5um (MWIR) and longwave 8-12um ( LWIR ) infrared spectra. Interest in...body photon radiation in the MWIR and LWIR spectral bands. With a significant black body photon radiation, passive night imaging and target

Quantum optics with nanowires (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zwiller, Val

2017-02-01

Nanowires offer new opportunities for nanoscale quantum optics; the quantum dot geometry in semiconducting nanowires as well as the material composition and environment can be engineered with unprecedented freedom to improve the light extraction efficiency. Quantum dots in nanowires are shown to be efficient single photon sources, in addition because of the very small fine structure splitting, we demonstrate the generation of entangled pairs of photons from a nanowire. By doping a nanowire and making ohmic contacts on both sides, a nanowire light emitting diode can be obtained with a single quantum dot as the active region. Under forward bias, this will act as an electrically pumped source of single photons. Under reverse bias, an avalanche effect can multiply photocurrent and enables the detection of single photons. Another type of nanowire under study in our group is superconducting nanowires for single photon detection, reaching efficiencies, time resolution and dark counts beyond currently available detectors. We will discuss our first attempts at combining semiconducting nanowire based single photon emitters and superconducting nanowire single photon detectors on a chip to realize integrated quantum circuits.

Sensors and detectors based on superconducting devices. July 1982-May 1990 (A Bibliography from the EI Engineering Meetings data base). Report for July 1982-May 1990

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1990-06-01

This bibliography contains citations from conference proceedings concerning gradiometers, magnetometers, and infrared detectors which use superconductors to improve sensitivity. Applications include biomagnetic measurements for medical studies, gravity wave experiments, geomagnetism and ocean bottom magnetic exploration, galvanometers and voltmeters, and bolometers and radiometers. Some articles refer to design considerations for cooling systems for the sensors and detectors, and fabrication techniques for squids (superconducting quantum interference devices.) (This updated bibliography contains 189 citations, 74 of which are new entries to the previous edition.)

Polarization entanglement purification of nonlocal microwave photons based on the cross-Kerr effect in circuit QED

NASA Astrophysics Data System (ADS)

Zhang, Hao; Liu, Qian; Xu, Xu-Sheng; Xiong, Jun; Alsaedi, Ahmed; Hayat, Tasawar; Deng, Fu-Guo

2017-11-01

Microwave photons have become very important qubits in quantum communication, as the first quantum satellite has been launched successfully. Therefore, it is a necessary and meaningful task for ensuring the high security and efficiency of microwave-based quantum communication in practice. Here, we present an original polarization entanglement purification protocol for nonlocal microwave photons based on the cross-Kerr effect in circuit quantum electrodynamics (QED). Our protocol can solve the problem that the purity of maximally entangled states used for constructing quantum channels will decrease due to decoherence from environment noise. This task is accomplished by means of the polarization parity-check quantum nondemolition (QND) detector, the bit-flipping operation, and the linear microwave elements. The QND detector is composed of several cross-Kerr effect systems which can be realized by coupling two superconducting transmission line resonators to a superconducting molecule with the N -type level structure. We give the applicable experimental parameters of QND measurement system in circuit QED and analyze the fidelities. Our protocol has good applications in long-distance quantum communication assisted by microwave photons in the future, such as satellite quantum communication.

NbN single-photon detectors with saturated dependence of quantum efficiency

NASA Astrophysics Data System (ADS)

Smirnov, Konstantin; Divochiy, Alexander; Vakhtomin, Yury; Morozov, Pavel; Zolotov, Philipp; Antipov, Andrey; Seleznev, Vitaliy

2018-07-01

The possibility of creating NbN superconducting single-photon detectors with saturated dependence of quantum efficiency (QE) versus normalized bias current was investigated. It was shown that the saturation increases for the detectors based on finer films with a lower value of R s300/R s20. The decreasing of R s300/R s20 was related to the increasing influence of quantum corrections to conductivity of superconductors and, in turn, to the decrease of the electron diffusion coefficient. The best samples have a constant value of system QE 94% at I b /I c ∼ 0.8 and wavelength 1310 nm.

Single photon detection of 1.5 THz radiation with the quantum capacitance detector

NASA Astrophysics Data System (ADS)

Echternach, P. M.; Pepper, B. J.; Reck, T.; Bradford, C. M.

2018-01-01

Far-infrared spectroscopy can reveal secrets of galaxy evolution and heavy-element enrichment throughout cosmic time, prompting astronomers worldwide to design cryogenic space telescopes for far-infrared spectroscopy. The most challenging aspect is a far-infrared detector that is both exquisitely sensitive (limited by the zodiacal-light noise in a narrow wavelength band, λ/Δλ 1,000) and array-able to tens of thousands of pixels. We present the quantum capacitance detector, a superconducting device adapted from quantum computing applications in which photon-produced free electrons in a superconductor tunnel into a small capacitive island embedded in a resonant circuit. The quantum capacitance detector has an optically measured noise equivalent power below 10-20 W Hz-1/2 at 1.5 THz, making it the most sensitive far-infrared detector ever demonstrated. We further demonstrate individual far-infrared photon counting, confirming the excellent sensitivity and suitability for cryogenic space astrophysics.

Quantum key distribution over 120 km using ultrahigh purity single-photon source and superconducting single-photon detectors.

PubMed

Takemoto, Kazuya; Nambu, Yoshihiro; Miyazawa, Toshiyuki; Sakuma, Yoshiki; Yamamoto, Tsuyoshi; Yorozu, Shinichi; Arakawa, Yasuhiko

2015-09-25

Advances in single-photon sources (SPSs) and single-photon detectors (SPDs) promise unique applications in the field of quantum information technology. In this paper, we report long-distance quantum key distribution (QKD) by using state-of-the-art devices: a quantum-dot SPS (QD SPS) emitting a photon in the telecom band of 1.5 μm and a superconducting nanowire SPD (SNSPD). At the distance of 100 km, we obtained the maximal secure key rate of 27.6 bps without using decoy states, which is at least threefold larger than the rate obtained in the previously reported 50-km-long QKD experiment. We also succeeded in transmitting secure keys at the rate of 0.307 bps over 120 km. This is the longest QKD distance yet reported by using known true SPSs. The ultralow multiphoton emissions of our SPS and ultralow dark count of the SNSPD contributed to this result. The experimental results demonstrate the potential applicability of QD SPSs to practical telecom QKD networks.

Ultrafast time measurements by time-correlated single photon counting coupled with superconducting single photon detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shcheslavskiy, V., E-mail: vis@becker-hickl.de; Becker, W.; Morozov, P.

Time resolution is one of the main characteristics of the single photon detectors besides quantum efficiency and dark count rate. We demonstrate here an ultrafast time-correlated single photon counting (TCSPC) setup consisting of a newly developed single photon counting board SPC-150NX and a superconducting NbN single photon detector with a sensitive area of 7 × 7 μm. The combination delivers a record instrument response function with a full width at half maximum of 17.8 ps and system quantum efficiency ∼15% at wavelength of 1560 nm. A calculation of the root mean square value of the timing jitter for channels withmore » counts more than 1% of the peak value yielded about 7.6 ps. The setup has also good timing stability of the detector–TCSPC board.« less

A scalable multi-photon coincidence detector based on superconducting nanowires.

PubMed

Zhu, Di; Zhao, Qing-Yuan; Choi, Hyeongrak; Lu, Tsung-Ju; Dane, Andrew E; Englund, Dirk; Berggren, Karl K

2018-06-04

Coincidence detection of single photons is crucial in numerous quantum technologies and usually requires multiple time-resolved single-photon detectors. However, the electronic readout becomes a major challenge when the measurement basis scales to large numbers of spatial modes. Here, we address this problem by introducing a two-terminal coincidence detector that enables scalable readout of an array of detector segments based on superconducting nanowire microstrip transmission line. Exploiting timing logic, we demonstrate a sixteen-element detector that resolves all 136 possible single-photon and two-photon coincidence events. We further explore the pulse shapes of the detector output and resolve up to four-photon events in a four-element device, giving the detector photon-number-resolving capability. This new detector architecture and operating scheme will be particularly useful for multi-photon coincidence detection in large-scale photonic integrated circuits.

Information on a Photon: Free-Space Quantum Communication (InPho: FSQC)

DTIC Science & Technology

2015-10-06

3 5 kHz . 9 InPho: FSQCSuperconducting nanowire detectors InPho Breakthrough – Develop 8 channel SiW superconducting... nanowire detectors optimized for 710 nm in collaboration with NIST Status report (6/4/14): Cryostat constructed, chill-down tests, detectors...similar jitter with custom circuit vs. MPD circuit allows for higher key rate and photon efficiency 27 InPho: FSQCSuperconducting nanowire detectors

Beam current sensor

DOEpatents

Kuchnir, M.; Mills, F.E.

1984-09-28

A current sensor for measuring the dc component of a beam of charged particles employs a superconducting pick-up loop probe, with twisted superconducting leads in combination with a Superconducting Quantum Interference Device (SQUID) detector. The pick-up probe is in the form of a single-turn loop, or a cylindrical toroid, through which the beam is directed and within which a first magnetic flux is excluded by the Meisner effect. The SQUID detector acts as a flux-to-voltage converter in providing a current to the pick-up loop so as to establish a second magnetic flux within the electrode which nulls out the first magnetic flux. A feedback voltage within the SQUID detector represents the beam current of the particles which transit the pick-up loop. Meisner effect currents prevent changes in the magnetic field within the toroidal pick-up loop and produce a current signal independent of the beam's cross-section and its position within the toroid, while the combination of superconducting elements provides current measurement sensitivities in the nano-ampere range.

Beam current sensor

DOEpatents

Kuchnir, Moyses; Mills, Frederick E.

1987-01-01

A current sensor for measuring the DC component of a beam of charged particles employs a superconducting pick-up loop probe, with twisted superconducting leads in combination with a Superconducting Quantum Interference Device (SQUID) detector. The pick-up probe is in the form of a single-turn loop, or a cylindrical toroid, through which the beam is directed and within which a first magnetic flux is excluded by the Meisner effect. The SQUID detector acts as a flux-to-voltage converter in providing a current to the pick-up loop so as to establish a second magnetic flux within the electrode which nulls out the first magnetic flux. A feedback voltage within the SQUID detector represents the beam current of the particles which transit the pick-up loop. Meisner effect currents prevent changes in the magnetic field within the toroidal pick-up loop and produce a current signal independent of the beam's cross-section and its position within the toroid, while the combination of superconducting elements provides current measurement sensitivites in the nano-ampere range.

Fermilab | Mu2e

Science.gov Websites

Interactions.org Particle Physics News Image Bank Fermilab in the News Quantum Diaries Mu2e: muon-to-electron works The Mu2e detector is a particle physics detector embedded in a series of superconducting magnets advance research at the Intensity Frontier. The U.S. Particle Physics Project Prioritization Panel, P5

Quantum key distribution over 120 km using ultrahigh purity single-photon source and superconducting single-photon detectors

PubMed Central

Takemoto, Kazuya; Nambu, Yoshihiro; Miyazawa, Toshiyuki; Sakuma, Yoshiki; Yamamoto, Tsuyoshi; Yorozu, Shinichi; Arakawa, Yasuhiko

2015-01-01

Advances in single-photon sources (SPSs) and single-photon detectors (SPDs) promise unique applications in the field of quantum information technology. In this paper, we report long-distance quantum key distribution (QKD) by using state-of-the-art devices: a quantum-dot SPS (QD SPS) emitting a photon in the telecom band of 1.5 μm and a superconducting nanowire SPD (SNSPD). At the distance of 100 km, we obtained the maximal secure key rate of 27.6 bps without using decoy states, which is at least threefold larger than the rate obtained in the previously reported 50-km-long QKD experiment. We also succeeded in transmitting secure keys at the rate of 0.307 bps over 120 km. This is the longest QKD distance yet reported by using known true SPSs. The ultralow multiphoton emissions of our SPS and ultralow dark count of the SNSPD contributed to this result. The experimental results demonstrate the potential applicability of QD SPSs to practical telecom QKD networks. PMID:26404010

High-speed and high-efficiency travelling wave single-photon detectors embedded in nanophotonic circuits

PubMed Central

Pernice, W.H.P.; Schuck, C.; Minaeva, O.; Li, M.; Goltsman, G.N.; Sergienko, A.V.; Tang, H.X.

2012-01-01

Ultrafast, high-efficiency single-photon detectors are among the most sought-after elements in modern quantum optics and quantum communication. However, imperfect modal matching and finite photon absorption rates have usually limited their maximum attainable detection efficiency. Here we demonstrate superconducting nanowire detectors atop nanophotonic waveguides, which enable a drastic increase of the absorption length for incoming photons. This allows us to achieve high on-chip single-photon detection efficiency up to 91% at telecom wavelengths, repeatable across several fabricated chips. We also observe remarkably low dark count rates without significant compromise of the on-chip detection efficiency. The detectors are fully embedded in scalable silicon photonic circuits and provide ultrashort timing jitter of 18 ps. Exploiting this high temporal resolution, we demonstrate ballistic photon transport in silicon ring resonators. Our direct implementation of a high-performance single-photon detector on chip overcomes a major barrier in integrated quantum photonics. PMID:23271658

Application of metallic magnetic calorimeter in rare event search

NASA Astrophysics Data System (ADS)

Kim, I.; Jo, H. S.; Kang, C. S.; Kim, G. B.; Kim, H. L.; Kim, S. R.; Kim, Y. H.; Lee, H. J.; Lee, J. H.; Lee, M. K.; Oh, S. Y.; So, J. H.

2017-09-01

Metallic magnetic calorimeters (MMCs) are highly sensitive temperature sensors that use the paramagnetic nature of erbium in a metallic host and superconducting electronics usually composed of a superconducting niobium coil and a current sensing superconducting quantum interference device. This article discusses the applicability of MMCs in experimental searches for rare events in particle physics. A detector module using two MMCs was built to perform low-temperature measurements of heat and scintillation light generated by particle interaction in a 340 g 40Ca100MoO4 crystal. The energy transfer mechanism, from incident particles to the components of the heat and light sensors, is described through a thermal model. MMCs, with gold films collecting athermal phonons, can be used over wide ranges of operating temperature and crystal volume without a significant change in detector performances. Rare event searches could thus benefit from MMC-based detectors presenting such flexibility as well as excellent energy resolution and particle discrimination power.

Waveguide-integrated single- and multi-photon detection at telecom wavelengths using superconducting nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferrari, Simone; Kahl, Oliver; Kovalyuk, Vadim

We investigate single- and multi-photon detection regimes of superconducting nanowire detectors embedded in silicon nitride nanophotonic circuits. At near-infrared wavelengths, simultaneous detection of up to three photons is observed for 120 nm wide nanowires biased far from the critical current, while narrow nanowires below 100 nm provide efficient single photon detection. A theoretical model is proposed to determine the different detection regimes and to calculate the corresponding internal quantum efficiency. The predicted saturation of the internal quantum efficiency in the single photon regime agrees well with plateau behavior observed at high bias currents.

Superconducting Detector Arrays for Astrophysics

NASA Technical Reports Server (NTRS)

Chervenak, James

2008-01-01

The next generation of astrophysics instruments will feature an order of magnitude more photon sensors or sensors that have an order of magnitude greater sensitivity. Since detector noise scales with temperature, a number of candidate technologies have been developed that use the intrinsic advantages of detector systems that operate below 1 Kelvin. Many of these systems employ of the superconducting phenomena that occur in metals at these temperatures to build ultrasensitive detectors and low-noise, low-power readout architectures. I will present one such system in use today to meet the needs of the astrophysics community at millimeter and x-ray wavelengths. Our group at NASA in collaboration with Princeton, NIST, Boulder and a number of other groups is building large format arrays of superconducting transition edge sensors (TES) read out with multiplexed superconducting quantum interference devices (SQUID). I will present the high sensitivity we have achieved in multiplexed x-ray sensors with the TES technology and describe the construction of a 1000-sensor TES/SQUID array for microwave measurements. With our collaboration's deployment of a kilopixel TES array for 2 mm radiation at the Atacarna Cosmology Telescope in November 2007, we have first images of the lensed Cosmic Microwave Background at fine angular scales.

Super Photon Counters

NASA Technical Reports Server (NTRS)

Mather, John

1999-01-01

The perfect photon detector would measure the arrival time, the energy, the polarization, and the position of every arriving quantum, but that is easier said than done. Two groups have now succeeded in doing time-resolved spectroscopy on the Crab Nebula pulsar, measuring everything but the polarization, with reports from Romani et al. at Stanford and from Perryman et al. at ESTEC. Both groups use superconducting detectors to gain the necessary speed and sensitivity. The photon can heat the electrons in a superconductor biased in the middle of its resistive transition, or break bound superconducting electron-hole pairs, which can then be collected. Three years ago, Peacock et al. reported that they had detected single optical photons with a superconducting tunnel junction (STJ), and Paresce wrote a News and Views article. A tunnel junction uses two pieces of conductive material, separated by a tiny gap of insulating material or even vacuum. If the gap is thin enough, electrons can tunnel across anyway, and if the conductors are superconductors, the junction displays very useful quantum mechanical properties and electrical nonlinearities. Amplifiers, detectors, oscillators, and computer circuits can all be made from them. Their special advantage is that they operate at very low temperatures, dissipate very little power, operate very fast, and are very small.

Far infrared through millimeter backshort-under-grid arrays

NASA Astrophysics Data System (ADS)

Allen, Christine A.; Abrahams, John; Benford, Dominic J.; Chervenak, James A.; Chuss, David T.; Staguhn, Johannes G.; Miller, Timothy M.; Moseley, S. Harvey; Wollack, Edward J.

2006-06-01

We are developing a large-format, versatile, bolometer array for a wide range of infrared through millimeter astronomical applications. The array design consists of three key components - superconducting transition edge sensor bolometer arrays, quarter-wave reflective backshort grids, and Superconducting Quantum Interference Device (SQUID) multiplexer readouts. The detector array is a filled, square grid of bolometers with superconducting sensors. The backshort arrays are fabricated separately and are positioned in the etch cavities behind the detector grid. The grids have unique three-dimensional interlocking features micromachined into the walls for positioning and mechanical stability. The ultimate goal of the program is to produce large-format arrays with background-limited sensitivity, suitable for a wide range of wavelengths and applications. Large-format (kilopixel) arrays will be directly indium bump bonded to a SQUID multiplexer circuit. We have produced and tested 8×8 arrays of 1 mm detectors to demonstrate proof of concept. 8×16 arrays of 2 mm detectors are being produced for a new Goddard Space Flight Center instrument. We have also produced models of a kilopixel detector grid and dummy multiplexer chip for bump bonding development. We present detector design overview, several unique fabrication highlights, and assembly technologies.

Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors

NASA Technical Reports Server (NTRS)

Stern, Jeffrey A.; Farr, William H.; Leduc, Henry G.; Bumble, Bruce

2008-01-01

Superconducting-nanowire single-photon detectors (SNSPDs) in which Nb(x)Ti(1-x)N (where x<1) films serve as the superconducting materials have shown promise as superior alternatives to previously developed SNSPDs in which NbN films serve as the superconducting materials. SNSPDs have potential utility in optical communications and quantum cryptography. Nb(x)Ti(1-x)N is a solid solution of NbN and TiN, and has many properties similar to those of NbN. It has been found to be generally easier to stabilize Nb(x)Ti(1-x)N in the high-superconducting-transition temperature phase than it is to so stabilize NbN. In addition, the resistivity and penetration depth of polycrystalline films of Nb(x)Ti(1-x)N have been found to be much smaller than those of films of NbN. These differences have been hypothesized to be attributable to better coupling at grain boundaries within Nb(x)Ti(1-x)N films.

Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors

NASA Technical Reports Server (NTRS)

Stem, Jeffrey A.; Farr, William H.; Leduc, Henry G.; Bumble, Bruce

2008-01-01

Superconducting-nanowire singlephoton detectors (SNSPDs) in which Nb(x)Ti(1-x)N (where x<1) films serve as the superconducting materials have shown promise as superior alternatives to previously developed SNSPDs in which NbN films serve as the superconducting materials. SNSPDs have potential utility in optical communications and quantum cryptography. Nb(x)Ti(1-x)N is a solid solution of NbN and TiN, and has many properties similar to those of NbN. It has been found to be generally easier to stabilize NbxTi1 xN in the high-superconducting-transitiontemperature phase than it is to so stabilize NbN. In addition, the resistivity and penetration depth of polycrystalline films of Nb(x)Ti(1-x)N have been found to be much smaller than those of films of NbN. These differences have been hypothesized to be attributable to better coupling at grain boundaries within Nb(x)Ti(1-x)N films.

Single-Shot Quantum Nondemolition Detection of Individual Itinerant Microwave Photons

NASA Astrophysics Data System (ADS)

Besse, Jean-Claude; Gasparinetti, Simone; Collodo, Michele C.; Walter, Theo; Kurpiers, Philipp; Pechal, Marek; Eichler, Christopher; Wallraff, Andreas

2018-04-01

Single-photon detection is an essential component in many experiments in quantum optics, but it remains challenging in the microwave domain. We realize a quantum nondemolition detector for propagating microwave photons and characterize its performance using a single-photon source. To this aim, we implement a cavity-assisted conditional phase gate between the incoming photon and a superconducting artificial atom. By reading out the state of this atom in a single shot, we reach an external (internal) photon-detection fidelity of 50% (71%), limited by transmission efficiency between the source and the detector (75%) and the coherence properties of the qubit. By characterizing the coherence and average number of photons in the field reflected off the detector, we demonstrate its quantum nondemolition nature. We envisage applications in generating heralded remote entanglement between qubits and for realizing logic gates between propagating microwave photons.

Frequency multiplexed superconducting quantum interference device readout of large bolometer arrays for cosmic microwave background measurements.

PubMed

Dobbs, M A; Lueker, M; Aird, K A; Bender, A N; Benson, B A; Bleem, L E; Carlstrom, J E; Chang, C L; Cho, H-M; Clarke, J; Crawford, T M; Crites, A T; Flanigan, D I; de Haan, T; George, E M; Halverson, N W; Holzapfel, W L; Hrubes, J D; Johnson, B R; Joseph, J; Keisler, R; Kennedy, J; Kermish, Z; Lanting, T M; Lee, A T; Leitch, E M; Luong-Van, D; McMahon, J J; Mehl, J; Meyer, S S; Montroy, T E; Padin, S; Plagge, T; Pryke, C; Richards, P L; Ruhl, J E; Schaffer, K K; Schwan, D; Shirokoff, E; Spieler, H G; Staniszewski, Z; Stark, A A; Vanderlinde, K; Vieira, J D; Vu, C; Westbrook, B; Williamson, R

2012-07-01

A technological milestone for experiments employing transition edge sensor bolometers operating at sub-Kelvin temperature is the deployment of detector arrays with 100s-1000s of bolometers. One key technology for such arrays is readout multiplexing: the ability to read out many sensors simultaneously on the same set of wires. This paper describes a frequency-domain multiplexed readout system which has been developed for and deployed on the APEX-SZ and South Pole Telescope millimeter wavelength receivers. In this system, the detector array is divided into modules of seven detectors, and each bolometer within the module is biased with a unique ∼MHz sinusoidal carrier such that the individual bolometer signals are well separated in frequency space. The currents from all bolometers in a module are summed together and pre-amplified with superconducting quantum interference devices operating at 4 K. Room temperature electronics demodulate the carriers to recover the bolometer signals, which are digitized separately and stored to disk. This readout system contributes little noise relative to the detectors themselves, is remarkably insensitive to unwanted microphonic excitations, and provides a technology pathway to multiplexing larger numbers of sensors.

Frequency-tuned microwave photon counter based on a superconductive quantum interferometer

NASA Astrophysics Data System (ADS)

Shnyrkov, V. I.; Yangcao, Wu; Soroka, A. A.; Turutanov, O. G.; Lyakhno, V. Yu.

2018-03-01

Various types of single-photon counters operating in infrared, ultraviolet, and optical wavelength ranges are successfully used to study electromagnetic fields, analyze radiation sources, and solve problems in quantum informatics. However, their operating principles become ineffective at millimeter band, S-band, and ultra-high frequency bands of wavelengths due to the decrease in quantum energy by 4-5 orders of magnitude. Josephson circuits with discrete Hamiltonians and qubits are a good foundation for the construction of single-photon counters at these frequencies. This paper presents a frequency-tuned microwave photon counter based on a single-junction superconducting quantum interferometer and flux qutrit. The control pulse converts the interferometer into a two-level system for resonance absorption of photons. Decay of the photon-induced excited state changes the magnetic flux in the interferometer, which is measured by a SQUID magnetometer. Schemes for recording the magnetic flux using a DC SQUID or ideal parametric detector, based on a qutrit with high-frequency excitation, are discussed. It is shown that the counter consisting of an interferometer with a Josephson junction and a parametric detector demonstrates high performance and is capable of detecting single photons in a microwave band.

Kinetic Inductance Photodetectors Based on Nonequilibrium Response in Superconducting Thin-Film Structures

NASA Technical Reports Server (NTRS)

Sergeev, A. V.; Karasik, B. S.; Gogidze, I. G.; Mitin, V. V.

2001-01-01

While experimental studies of kinetic-inductance sensors have been limited so far by the temperature range near the superconducting transition, these detectors can be very sensitivity at temperatures well below the transition, where the number of equilibrium quasiparticles is exponentially small. In this regime, a shift of the quasiparticle chemical potential under radiation results in the change of the kinetic inductance, which can be measured by a sensitive SQUID readout. We modeled the kinetic inductance response of detectors made from disordered superconducting Nb, NbC, and MoRe films. Low phonon transparency of the interface between the superconductor and the substrate causes substantial re-trapping of phonons providing high quantum efficiency and the operating time of approximately 1 ms at 1 K. Due to the small number of quasiparticles, the noise equivalent power of the detector determined by the quasiparticle generation-recombination noise can be as small as approximately 10(exp -19) W/Hz(exp 1/2) at He4 temperatures.

Investigation of the Performance of an Ultralow-Dark-Count Superconducting Nanowire Single-Photon Detector

NASA Astrophysics Data System (ADS)

Subashchandran, Shanthi; Okamoto, Ryo; Zhang, Labao; Tanaka, Akira; Okano, Masayuki; Kang, Lin; Chen, Jian; Wu, Peiheng; Takeuchi, Shigeki

2013-10-01

The realization of an ultralow-dark-count rate (DCR) along with the conservation of high detection efficiency (DE) is critical for many applications using single photon detectors in quantum information technologies, material sciences, and biological sensing. For this purpose, a fiber-coupled superconducting nanowire single-photon detector (SNSPD) with a meander-type niobium nitride nanowire (width: 50 nm) is studied. Precise measurements of the bias current dependence of DE are carried out for a wide spectral range (from 500 to 1650 nm in steps of 50 nm) using a white light source and a laser line Bragg tunable band-pass filter. An ultralow DCR (0.0015 cps) and high DE (32%) are simultaneously achieved by the SNSPD at a wavelength of 500 nm.

Superconductivity: Recent Developments and Defence Applications

DTIC Science & Technology

1988-03-11

resonance tomography ; quantum interferometers used in detectors for research into biomagnetism and gravitational waves; and analogue electronics devices...has looked at muon spin rotation measurements of the penetration depth of magnetic fields into the superconductors. Basic research is under way at Chalk

Microfiber-coupled superconducting nanowire single-photon detector for near-infrared wavelengths.

PubMed

You, Lixing; Wu, Junjie; Xu, Yingxin; Hou, Xintong; Fang, Wei; Li, Hao; Zhang, Weijun; Zhang, Lu; Liu, Xiaoyu; Tong, Limin; Wang, Zhen; Xie, Xiaoming

2017-12-11

High-performance superconducting nanowire single-photon detectors (SNSPDs) have facilitated numerous experiments and applications, particularly in the fields of modern quantum optics and quantum communication. Two kinds of optical coupling methods have thus far been developed for SNSPDs: one produces standard fiber-coupled SNSPDs in which the fibers vertically illuminate the meandered nanowires; the other produces waveguide-coupled SNSPDs in which nanowires are fabricated on the surface of a waveguide that guides photons, and the fibers are coupled to the waveguide. In this paper, we report on first experimental demonstration of a new type of SNSPD that is coupled with a microfiber (MF). Photons are guided by the MF and are evanescently absorbed by the nanowires of the SNSPD when the MF is placed on top of superconducting NbN nanowires. Room-temperature optical experiments indicated that this device has a coupling efficiency of up to 90% when a 1.3 μm-diameter MF is used for light with wavelength of 1550 nm. We were also able to demonstrate that our MF-coupled detector achieved system detection efficiencies of 50% and 20% at incident wavelengths of 1064 and 1550 nm, respectively, for a 2 μm-diameter MF at 2.2K. We expect that MF-coupled SNSPDs may show both high efficiency and broadband characteristics upon optimization and will be used for various novel applications, such as micro/nano-fiber optics.

Quantum Key Distribution Using Polarized Single Photons

DTIC Science & Technology

2009-04-01

liquid helium the SSPD with a low - noise , cryogenic high-electron-mobility transistor (HEMT) with high-input impedance. This arrangement allowed us...Sobolewski, IEEE Trans. Appl. Supercon., accepted (2009). 19. " Measurements of amplitude distributions of dark counts and photon counts in NbN ...75, 174507 (2007). 6. "Fiber-Coupled NbN Superconducting Single-Photon Detectors for Quantum Correlation Measurements ," W. Slysz, M. Wegrzecki, J

Free-space-coupled superconducting nanowire single-photon detectors for infrared optical communications.

PubMed

Bellei, Francesco; Cartwright, Alyssa P; McCaughan, Adam N; Dane, Andrew E; Najafi, Faraz; Zhao, Qingyuan; Berggren, Karl K

2016-02-22

This paper describes the construction of a cryostat and an optical system with a free-space coupling efficiency of 56.5% ± 3.4% to a superconducting nanowire single-photon detector (SNSPD) for infrared quantum communication and spectrum analysis. A 1K pot decreases the base temperature to T = 1.7 K from the 2.9 K reached by the cold head cooled by a pulse-tube cryocooler. The minimum spot size coupled to the detector chip was 6.6 ± 0.11 µm starting from a fiber source at wavelength, λ = 1.55 µm. We demonstrated photon counting on a detector with an 8 × 7.3 µm2 area. We measured a dark count rate of 95 ± 3.35 kcps and a system detection efficiency of 1.64% ± 0.13%. We explain the key steps that are required to improve further the coupling efficiency.

Integrated autocorrelator based on superconducting nanowires.

PubMed

Sahin, Döndü; Gaggero, Alessandro; Hoang, Thang Ba; Frucci, Giulia; Mattioli, Francesco; Leoni, Roberto; Beetz, Johannes; Lermer, Matthias; Kamp, Martin; Höfling, Sven; Fiore, Andrea

2013-05-06

We demonstrate an integrated autocorrelator based on two superconducting single-photon detectors patterned on top of a GaAs ridge waveguide. This device enables the on-chip measurement of the second-order intensity correlation function g(2)(τ). A polarization-independent device quantum efficiency in the 1% range is reported, with a timing jitter of 88 ps at 1300 nm. g(2)(τ) measurements of continuous-wave and pulsed laser excitations are demonstrated with no measurable crosstalk within our measurement accuracy.

Measurement-Device-Independent Quantum Key Distribution over 200 km

NASA Astrophysics Data System (ADS)

Tang, Yan-Lin; Yin, Hua-Lei; Chen, Si-Jing; Liu, Yang; Zhang, Wei-Jun; Jiang, Xiao; Zhang, Lu; Wang, Jian; You, Li-Xing; Guan, Jian-Yu; Yang, Dong-Xu; Wang, Zhen; Liang, Hao; Zhang, Zhen; Zhou, Nan; Ma, Xiongfeng; Chen, Teng-Yun; Zhang, Qiang; Pan, Jian-Wei

2014-11-01

Measurement-device-independent quantum key distribution (MDIQKD) protocol is immune to all attacks on detection and guarantees the information-theoretical security even with imperfect single-photon detectors. Recently, several proof-of-principle demonstrations of MDIQKD have been achieved. Those experiments, although novel, are implemented through limited distance with a key rate less than 0.1 bit /s . Here, by developing a 75 MHz clock rate fully automatic and highly stable system and superconducting nanowire single-photon detectors with detection efficiencies of more than 40%, we extend the secure transmission distance of MDIQKD to 200 km and achieve a secure key rate 3 orders of magnitude higher. These results pave the way towards a quantum network with measurement-device-independent security.

On-chip detection of non-classical light by scalable integration of single-photon detectors

PubMed Central

Najafi, Faraz; Mower, Jacob; Harris, Nicholas C.; Bellei, Francesco; Dane, Andrew; Lee, Catherine; Hu, Xiaolong; Kharel, Prashanta; Marsili, Francesco; Assefa, Solomon; Berggren, Karl K.; Englund, Dirk

2015-01-01

Photonic-integrated circuits have emerged as a scalable platform for complex quantum systems. A central goal is to integrate single-photon detectors to reduce optical losses, latency and wiring complexity associated with off-chip detectors. Superconducting nanowire single-photon detectors (SNSPDs) are particularly attractive because of high detection efficiency, sub-50-ps jitter and nanosecond-scale reset time. However, while single detectors have been incorporated into individual waveguides, the system detection efficiency of multiple SNSPDs in one photonic circuit—required for scalable quantum photonic circuits—has been limited to <0.2%. Here we introduce a micrometer-scale flip-chip process that enables scalable integration of SNSPDs on a range of photonic circuits. Ten low-jitter detectors are integrated on one circuit with 100% device yield. With an average system detection efficiency beyond 10%, and estimated on-chip detection efficiency of 14–52% for four detectors operated simultaneously, we demonstrate, to the best of our knowledge, the first on-chip photon correlation measurements of non-classical light. PMID:25575346

Imaging the Working Brain.

ERIC Educational Resources Information Center

Swithenby, S. J.

1996-01-01

Very sensitive SQUID (superconducting quantum interference device) detectors are used in the technique known as magnetoencephalography to provide dynamic images of the brain. This can help our fundamental understanding of the way the brain works and may be of particular use in treating disorders such as epilepsy. (Author/MKR)

High sensitive THz superconducting hot electron bolometer mixers and transition edge sensors

NASA Astrophysics Data System (ADS)

Zhang, W.; Miao, W.; Zhou, K. M.; Guo, X. H.; Zhong, J. Q.; Shi, S. C.

2016-11-01

Terahertz band, which is roughly defined as 0.1 THz to 10 THz, is an interesting frequency region of the electromagnetic spectrum to be fully explored in astronomy. THz observations play key roles in astrophysics and cosmology. High sensitive heterodyne and direct detectors are the main tools for the detection of molecular spectral lines and fine atomic structure spectral lines, which are very important tracers for probing the physical and chemical properties and dynamic processes of objects such as star and planetary systems. China is planning to build an THz telescope at Dome A, Antarctica, a unique site for ground-based THz observations. We are developing THz superconducting hot electron bolometer (HEB) mixers and transition edge sensors (TES), which are quantum limited and back-ground limited detectors, respectively. Here we first introduce the working principles of superconducting HEB and TES, and then mainly present the results achieved at Purple mountain Observatory.

High quantum efficiency and low dark count rate in multi-layer superconducting nanowire single-photon detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jafari Salim, A., E-mail: ajafaris@uwaterloo.ca; Eftekharian, A.; University of Waterloo, Waterloo, Ontario N2L 3G1

In this paper, we theoretically show that a multi-layer superconducting nanowire single-photon detector (SNSPD) is capable of approaching characteristics of an ideal SNSPD in terms of the quantum efficiency, dark count, and band-width. A multi-layer structure improves the performance in two ways. First, the potential barrier for thermally activated vortex crossing, which is the major source of dark counts and the reduction of the critical current in SNSPDs is elevated. In a multi-layer SNSPD, a vortex is made of 2D-pancake vortices that form a stack. It will be shown that the stack of pancake vortices effectively experiences a larger potentialmore » barrier compared to a vortex in a single-layer SNSPD. This leads to an increase in the experimental critical current as well as significant decrease in the dark count rate. In consequence, an increase in the quantum efficiency for photons of the same energy or an increase in the sensitivity to photons of lower energy is achieved. Second, a multi-layer structure improves the efficiency of single-photon absorption by increasing the effective optical thickness without compromising the single-photon sensitivity.« less

Physics and Applications of Metallic Magnetic Calorimeters

NASA Astrophysics Data System (ADS)

Kempf, S.; Fleischmann, A.; Gastaldo, L.; Enss, C.

2018-03-01

Metallic magnetic calorimeters (MMCs) are calorimetric low-temperature particle detectors that are currently strongly advancing the state of the art in energy-dispersive single particle detection. They are typically operated at temperatures below 100 mK and make use of a metallic, paramagnetic temperature sensor to transduce the temperature rise of the detector upon the absorption of an energetic particle into a change of magnetic flux which is sensed by a superconducting quantum interference device. This outstanding interplay between a high-sensitivity thermometer and a near quantum-limited amplifier results in a very fast signal rise time, an excellent energy resolution, a large dynamic range, a quantum efficiency close to 100% as well as an almost ideal linear detector response. For this reason, a growing number of groups located all over the world is developing MMC arrays of various sizes which are routinely used in a variety of applications. Within this paper, we briefly review the state of the art of metallic magnetic calorimeters. This includes a discussion of the detection principle, sensor materials and detector geometries, readout concepts, the structure of modern detectors as well as the state-of-the-art detector performance.

Observing Quantum State Diffusion by Heterodyne Detection of Fluorescence

NASA Astrophysics Data System (ADS)

Campagne-Ibarcq, P.; Six, P.; Bretheau, L.; Sarlette, A.; Mirrahimi, M.; Rouchon, P.; Huard, B.

2016-01-01

A qubit can relax by fluorescence, which prompts the release of a photon into its electromagnetic environment. By counting the emitted photons, discrete quantum jumps of the qubit state can be observed. The succession of states occupied by the qubit in a single experiment, its quantum trajectory, depends in fact on the kind of detector. How are the quantum trajectories modified if one measures continuously the amplitude of the fluorescence field instead? Using a superconducting parametric amplifier, we perform heterodyne detection of the fluorescence of a superconducting qubit. For each realization of the measurement record, we can reconstruct a different quantum trajectory for the qubit. The observed evolution obeys quantum state diffusion, which is characteristic of quantum measurements subject to zero-point fluctuations. Independent projective measurements of the qubit at various times provide a quantitative verification of the reconstructed trajectories. By exploring the statistics of quantum trajectories, we demonstrate that the qubit states span a deterministic surface in the Bloch sphere at each time in the evolution. Additionally, we show that when monitoring fluorescence field quadratures, coherent superpositions are generated during the decay from excited to ground state. Counterintuitively, measuring light emitted during relaxation can give rise to trajectories with increased excitation probability.

Quantum interference in plasmonic circuits.

PubMed

Heeres, Reinier W; Kouwenhoven, Leo P; Zwiller, Valery

2013-10-01

Surface plasmon polaritons (plasmons) are a combination of light and a collective oscillation of the free electron plasma at metal/dielectric interfaces. This interaction allows subwavelength confinement of light beyond the diffraction limit inherent to dielectric structures. As a result, the intensity of the electromagnetic field is enhanced, with the possibility to increase the strength of the optical interactions between waveguides, light sources and detectors. Plasmons maintain non-classical photon statistics and preserve entanglement upon transmission through thin, patterned metallic films or weakly confining waveguides. For quantum applications, it is essential that plasmons behave as indistinguishable quantum particles. Here we report on a quantum interference experiment in a nanoscale plasmonic circuit consisting of an on-chip plasmon beamsplitter with integrated superconducting single-photon detectors to allow efficient single plasmon detection. We demonstrate a quantum-mechanical interaction between pairs of indistinguishable surface plasmons by observing Hong-Ou-Mandel (HOM) interference, a hallmark non-classical interference effect that is the basis of linear optics-based quantum computation. Our work shows that it is feasible to shrink quantum optical experiments to the nanoscale and offers a promising route towards subwavelength quantum optical networks.

Backshort-Under-Grid arrays for infrared astronomy

NASA Astrophysics Data System (ADS)

Allen, C. A.; Benford, D. J.; Chervenak, J. A.; Chuss, D. T.; Miller, T. M.; Moseley, S. H.; Staguhn, J. G.; Wollack, E. J.

2006-04-01

We are developing a kilopixel, filled bolometer array for space infrared astronomy. The array consists of three individual components, to be merged into a single, working unit; (1) a transition edge sensor bolometer array, operating in the milliKelvin regime, (2) a quarter-wave backshort grid, and (3) superconducting quantum interference device multiplexer readout. The detector array is designed as a filled, square grid of suspended, silicon bolometers with superconducting sensors. The backshort arrays are fabricated separately and will be positioned in the cavities created behind each detector during fabrication. The grids have a unique interlocking feature machined into the walls for positioning and mechanical stability. The spacing of the backshort beneath the detector grid can be set from ˜30 300 μm, by independently adjusting two process parameters during fabrication. The ultimate goal is to develop a large-format array architecture with background-limited sensitivity, suitable for a wide range of wavelengths and applications, to be directly bump bonded to a multiplexer circuit. We have produced prototype two-dimensional arrays having 8×8 detector elements. We present detector design, fabrication overview, and assembly technologies.

Detecting Axion Dark Matter with Superconducting Qubits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dixit, Akash; Chou, Aaron; Schuster, David

Axion dark matter haloscopes aim to detect dark matter axions converting to single photons in resonant cavities bathed in a uniform magnetic field. A qubit (two level system) operating as a single microwave photon detector is a viable readout system for such detectors and may offer advantages over the quantum limited amplifiers currently used. When weakly coupled to the detection cavity, the qubit transition frequency is shifted by an amount proportional to the cavity photon number. Through spectroscopy of the qubit, the frequency shift is measured and the cavity occupation number is extracted. At low enough temperatures, this would allowmore » sensitivities exceeding that of the standard quantum limit.« less

The Department of Defense Superconductivity Research and Development (DSRD) Options. A Study of Possible Directions for Exploitation of Superconductivity in Military Applications.

DTIC Science & Technology

1987-07-01

transmission lines Low - noise mm wave detectors, mixers and amplifiers Multi-GHz chirp transform processors High performance small antenna arrays Multi-GHz A/D...attractive alternative. The overall advantages for HTS mm wave receivers are very- low quantum-limited noise , wide bandwidth, low electrical power...0 0 3 2 1 6 6.3A 0 0 0 2 -3 S Total 2 2 4 S 4 17 116 10, ELF Communication (far term). Extremely low frequency communication via magnetic wave has

NASA Office of Aeronautics and Space Technology Summer Workshop. Volume 10: Basic research panel

NASA Technical Reports Server (NTRS)

1975-01-01

Possible research experiments using the space transportation system are identified based on user requirements. Opportunity driven research areas include quantum electronics, cryogenics system technology, superconducting devices and detectors, and photo-induced reactions. Mission driven research requirements were examined and ranked based on inputs from the user group.

Superconductor-superconductor bilayers for enhancing single-photon detection

NASA Astrophysics Data System (ADS)

Ivry, Yachin; Surick, Jonathan J.; Barzilay, Maya; Kim, Chung-Soo; Najafi, Faraz; Kalfon-Cohen, Estelle; Dane, Andrew D.; Berggren, Karl K.

2017-10-01

Here, we optimized ultrathin films of granular NbN on SiO2 and of amorphous αW5Si3. We showed that hybrid superconducting nanowire single-photon detectors (SNSPDs) made of 2 nm thick αW5Si3 films over 2 nm thick NbN films exhibit advantageous coexistence of timing (<5 ns reset time and 52 ps timing jitter) and efficiency (>96% quantum efficiency) performance. We discuss the governing mechanism of this hybridization via the proximity effect. Our results demonstrate saturated SNSPDs performance at 1550 nm optical wavelength and suggest that such hybridization can significantly expand the range of available superconducting properties, impacting other nano-superconducting technologies. Lastly, this hybridization may be used to tune properties, such as the amorphous character of superconducting films.

The Large Hadron Collider (LHC): The Energy Frontier

NASA Astrophysics Data System (ADS)

Brianti, Giorgio; Jenni, Peter

The following sections are included: * Introduction * Superconducting Magnets: Powerful, Precise, Plentiful * LHC Cryogenics: Quantum Fluids at Work * Current Leads: High Temperature Superconductors to the Fore * A Pumping Vacuum Chamber: Ultimate Simplicity * Vertex Detectors at LHC: In Search of Beauty * Large Silicon Trackers: Fast, Precise, Efficient * Two Approaches to High Resolution Electromagnetic Calorimetry * Multigap Resistive Plate Chamber: Chronometry of Particles * The LHCb RICH: The Lord of the Cherenkov Rings * Signal Processing: Taming the LHC Data Avalanche * Giant Magnets for Giant Detectors

The SuperCDMS SNOLAB Detector Tower

NASA Astrophysics Data System (ADS)

Aramaki, Tsuguo

2016-08-01

The SuperCDMS collaboration is moving forward with the design and construction of SuperCDMS SNOLAB, where the initial deployment will include ˜ 30 kg of Ge and ˜ 5 kg of Si detectors. Here, we will discuss the associated cryogenic cold hardware required for the detector readout. The phonon signals will be read out with superconducting quantum interference device arrays and the ionization signals will use high electron mobility transistor amplifiers operating at 4 K. A number of design challenges exist regarding the required wiring complex impedance, noise pickup, vibration, and thermal isolation. Our progress to date will be presented.

Recent advances in superconducting-mixer simulations

NASA Technical Reports Server (NTRS)

Withington, S.; Kennedy, P. R.

1992-01-01

Over the last few years, considerable progress have been made in the development of techniques for fabricating high-quality superconducting circuits, and this success, together with major advances in the theoretical understanding of quantum detection and mixing at millimeter and submillimeter wavelengths, has made the development of CAD techniques for superconducting nonlinear circuits an important new enterprise. For example, arrays of quasioptical mixers are now being manufactured, where the antennas, matching networks, filters and superconducting tunnel junctions are all fabricated by depositing niobium and a variety of oxides on a single quartz substrate. There are no adjustable tuning elements on these integrated circuits, and therefore, one must be able to predict their electrical behavior precisely. This requirement, together with a general interest in the generic behavior of devices such as direct detectors and harmonic mixers, has lead us to develop a range of CAD tools for simulating the large-signal, small-signal, and noise behavior of superconducting tunnel junction circuits.

A twofold quantum delayed-choice experiment in a superconducting circuit

PubMed Central

Liu, Ke; Xu, Yuan; Wang, Weiting; Zheng, Shi-Biao; Roy, Tanay; Kundu, Suman; Chand, Madhavi; Ranadive, Arpit; Vijay, Rajamani; Song, Yipu; Duan, Luming; Sun, Luyan

2017-01-01

Wave-particle complementarity lies at the heart of quantum mechanics. To illustrate this mysterious feature, Wheeler proposed the delayed-choice experiment, where a quantum system manifests the wave- or particle-like attribute, depending on the experimental arrangement, which is made after the system has entered the interferometer. In recent quantum delayed-choice experiments, these two complementary behaviors were simultaneously observed with a quantum interferometer in a superposition of being closed and open. We suggest and implement a conceptually different quantum delayed-choice experiment by introducing a which-path detector (WPD) that can simultaneously record and neglect the system’s path information, but where the interferometer itself is classical. Our experiment is realized with a superconducting circuit, where a cavity acts as the WPD for an interfering qubit. Using this setup, we implement the first twofold delayed-choice experiment, which demonstrates that the system’s behavior depends not only on the measuring device’s configuration that can be chosen even after the system has been detected but also on whether we a posteriori erase or mark the which-path information, the latter of which cannot be revealed by previous quantum delayed-choice experiments. Our results represent the first demonstration of both counterintuitive features with the same experimental setup, significantly extending the concept of quantum delayed-choice experiment. PMID:28508079

A twofold quantum delayed-choice experiment in a superconducting circuit.

PubMed

Liu, Ke; Xu, Yuan; Wang, Weiting; Zheng, Shi-Biao; Roy, Tanay; Kundu, Suman; Chand, Madhavi; Ranadive, Arpit; Vijay, Rajamani; Song, Yipu; Duan, Luming; Sun, Luyan

2017-05-01

Wave-particle complementarity lies at the heart of quantum mechanics. To illustrate this mysterious feature, Wheeler proposed the delayed-choice experiment, where a quantum system manifests the wave- or particle-like attribute, depending on the experimental arrangement, which is made after the system has entered the interferometer. In recent quantum delayed-choice experiments, these two complementary behaviors were simultaneously observed with a quantum interferometer in a superposition of being closed and open. We suggest and implement a conceptually different quantum delayed-choice experiment by introducing a which-path detector (WPD) that can simultaneously record and neglect the system's path information, but where the interferometer itself is classical. Our experiment is realized with a superconducting circuit, where a cavity acts as the WPD for an interfering qubit. Using this setup, we implement the first twofold delayed-choice experiment, which demonstrates that the system's behavior depends not only on the measuring device's configuration that can be chosen even after the system has been detected but also on whether we a posteriori erase or mark the which-path information, the latter of which cannot be revealed by previous quantum delayed-choice experiments. Our results represent the first demonstration of both counterintuitive features with the same experimental setup, significantly extending the concept of quantum delayed-choice experiment.

UV superconducting nanowire single-photon detectors with high efficiency, low noise, and 4 K operating temperature

NASA Astrophysics Data System (ADS)

Wollman, E. E.; Verma, V. B.; Beyer, A. D.; Briggs, R. M.; Korzh, B.; Allmaras, J. P.; Marsili, F.; Lita, A. E.; Mirin, R. P.; Nam, S. W.; Shaw, M. D.

2017-10-01

For photon-counting applications at ultraviolet wavelengths, there are currently no detectors that combine high efficiency (> 50%), sub-nanosecond timing resolution, and sub-Hz dark count rates. Superconducting nanowire single-photon detectors (SNSPDs) have seen success over the past decade for photon-counting applications in the near-infrared, but little work has been done to optimize SNSPDs for wavelengths below 400 nm. Here, we describe the design, fabrication, and characterization of UV SNSPDs operating at wavelengths between 250 and 370 nm. The detectors have active areas up to 56 ${\\mu}$m in diameter, 70 - 80% efficiency, timing resolution down to 60 ps FWHM, blindness to visible and infrared photons, and dark count rates of ~ 0.25 counts/hr for a 56 ${\\mu}$m diameter pixel. By using the amorphous superconductor MoSi, these UV SNSPDs are also able to operate at temperatures up to 4.2 K. These performance metrics make UV SNSPDs ideal for applications in trapped-ion quantum information processing, lidar studies of the upper atmosphere, UV fluorescent-lifetime imaging microscopy, and photon-starved UV astronomy.

Fabrication and Characterization of Superconducting Resonators

PubMed Central

Cataldo, Giuseppe; Barrentine, Emily M.; Brown, Ari D.; Moseley, Samuel H.; U-Yen, Kongpop; Wollack, Edward J.

2016-01-01

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors (MKIDs) for the detection of faint astrophysical signatures, as well as for quantum computing applications and materials characterization. In this paper, procedures are presented for the fabrication and characterization of thin-film superconducting microwave resonators. The fabrication methodology allows for the realization of superconducting transmission-line resonators with features on both sides of an atomically smooth single-crystal silicon dielectric. This work describes the procedure for the installation of resonator devices into a cryogenic microwave testbed and for cool-down below the superconducting transition temperature. The set-up of the cryogenic microwave testbed allows one to do careful measurements of the complex microwave transmission of these resonator devices, enabling the extraction of the properties of the superconducting lines and dielectric substrate (e.g., internal quality factors, loss and kinetic inductance fractions), which are important for device design and performance. PMID:27284966

Weakly superconducting, thin-film structures as radiation detectors.

NASA Technical Reports Server (NTRS)

Kirschman, R. K.

1972-01-01

Measurements were taken with weakly superconducting quantum structures of the Notarys-Mercereau type, representing a thin superconductor film with a short region that is weakened in the sense that its transition temperature is lower than in the remaining portion of the film. The structure acts as a superconducting relaxation oscillator in which the supercurrent increases with time until the critical current of the weakened section is attained, at which moment the supercurrent decays and the cycle repeats. Under applied radiation, a series of constant-voltage steps appears in the current-voltage curve, and the size of the steps varies periodically with the amplitude of applied radiation. Measurements of the response characteristics were made in the frequency range of 10 to 450 MHz.

European roadmap on superconductive electronics - status and perspectives

NASA Astrophysics Data System (ADS)

Anders, S.; Blamire, M. G.; Buchholz, F.-Im.; Crété, D.-G.; Cristiano, R.; Febvre, P.; Fritzsch, L.; Herr, A.; Il'ichev, E.; Kohlmann, J.; Kunert, J.; Meyer, H.-G.; Niemeyer, J.; Ortlepp, T.; Rogalla, H.; Schurig, T.; Siegel, M.; Stolz, R.; Tarte, E.; ter Brake, H. J. M.; Toepfer, H.; Villegier, J.-C.; Zagoskin, A. M.; Zorin, A. B.

2010-12-01

Executive SummaryFor four decades semiconductor electronics has followed Moore’s law: with each generation of integration the circuit features became smaller, more complex and faster. This development is now reaching a wall so that smaller is no longer any faster. The clock rate has saturated at about 3-5 GHz and the parallel processor approach will soon reach its limit. The prime reason for the limitation the semiconductor electronics experiences is not the switching speed of the individual transistor, but its power dissipation and thus heat. Digital superconductive electronics is a circuit- and device-technology that is inherently faster at much less power dissipation than semiconductor electronics. It makes use of superconductors and Josephson junctions as circuit elements, which can provide extremely fast digital devices in a frequency range - dependent on the material - of hundreds of GHz: for example a flip-flop has been demonstrated that operated at 750 GHz. This digital technique is scalable and follows similar design rules as semiconductor devices. Its very low power dissipation of only 0.1 μW per gate at 100 GHz opens the possibility of three-dimensional integration. Circuits like microprocessors and analogue-to-digital converters for commercial and military applications have been demonstrated. In contrast to semiconductor circuits, the operation of superconducting circuits is based on naturally standardized digital pulses the area of which is exactly the flux quantum Φ0. The flux quantum is also the natural quantization unit for digital-to-analogue and analogue-to-digital converters. The latter application is so precise, that it is being used as voltage standard and that the physical unit ‘Volt’ is defined by means of this standard. Apart from its outstanding features for digital electronics, superconductive electronics provides also the most sensitive sensor for magnetic fields: the Superconducting Quantum Interference Device (SQUID). Amongst many other applications SQUIDs are used as sensors for magnetic heart and brain signals in medical applications, as sensor for geological surveying and food-processing and for non-destructive testing. As amplifiers of electrical signals, SQUIDs can nearly reach the theoretical limit given by Quantum Mechanics. A further important field of application is the detection of very weak signals by ‘transition-edge’ bolometers, superconducting nanowire single-photon detectors, and superconductive tunnel junctions. Their application as radiation detectors in a wide frequency range, from microwaves to X-rays is now standard. The very low losses of superconductors have led to commercial microwave filter designs that are now widely used in the USA in base stations for cellular phones and in military communication applications. The number of demonstrated applications is continuously increasing and there is no area in professional electronics, in which superconductive electronics cannot be applied and surpasses the performance of classical devices. Superconductive electronics has to be cooled to very low temperatures. Whereas this was a bottleneck in the past, cooling techniques have made a huge step forward in recent years: very compact systems with high reliability and a wide range of cooling power are available commercially, from microcoolers of match-box size with milli-Watt cooling power to high-reliability coolers of many Watts of cooling power for satellite applications. Superconductive electronics will not replace semiconductor electronics and similar room-temperature techniques in standard applications, but for those applications which require very high speed, low-power consumption, extreme sensitivity or extremely high precision, superconductive electronics is superior to all other available techniques. To strengthen the European competitiveness in superconductor electronics research projects have to be set-up in the following field: Ultra-sensitive sensing and imaging. Quantum measurement instrumentation. Advanced analogue-to-digital converters. Superconductive electronics technology.

Superconducting quantum circuits theory and application

NASA Astrophysics Data System (ADS)

Deng, Xiuhao

Superconducting quantum circuit models are widely used to understand superconducting devices. This thesis consists of four studies wherein the superconducting quantum circuit is used to illustrate challenges related to quantum information encoding and processing, quantum simulation, quantum signal detection and amplification. The existence of scalar Aharanov-Bohm phase has been a controversial topic for decades. Scalar AB phase, defined as time integral of electric potential, gives rises to an extra phase factor in wavefunction. We proposed a superconducting quantum Faraday cage to detect temporal interference effect as a consequence of scalar AB phase. Using the superconducting quantum circuit model, the physical system is solved and resulting AB effect is predicted. Further discussion in this chapter shows that treating the experimental apparatus quantum mechanically, spatial scalar AB effect, proposed by Aharanov-Bohm, can't be observed. Either a decoherent interference apparatus is used to observe spatial scalar AB effect, or a quantum Faraday cage is used to observe temporal scalar AB effect. The second study involves protecting a quantum system from losing coherence, which is crucial to any practical quantum computation scheme. We present a theory to encode any qubit, especially superconducting qubits, into a universal quantum degeneracy point (UQDP) where low frequency noise is suppressed significantly. Numerical simulations for superconducting charge qubit using experimental parameters show that its coherence time is prolong by two orders of magnitude using our universal degeneracy point approach. With this improvement, a set of universal quantum gates can be performed at high fidelity without losing too much quantum coherence. Starting in 2004, the use of circuit QED has enabled the manipulation of superconducting qubits with photons. We applied quantum optical approach to model coupled resonators and obtained a four-wave mixing toolbox to operate photons states. The model and toolbox are engineered with a superconducting quantum circuit where two superconducting resonators are coupled via the UQDP circuit. Using fourth order perturbation theory one can realize a complete set of quantum operations between these two photon modes. This helps open a new field to treat photon modes as qubits. Additional, a three-wave mixing scheme using phase qubits permits one to engineer the coupling Hamiltonian using a phase qubit as a tunable coupler. Along with Feynman's idea using quantum to simulate quantum, superconducting quantum simulators have been studied intensively recently. Taking the advantage of mesoscopic size of superconducting circuit and local tunability, we came out the idea to simulate quantum phase transition due to disorder. Our first paper was to propose a superconducting quantum simulator of Bose-Hubbard model to do site-wise manipulation and observe Mott-insulator to superfluid phase transition. The side-band cooling of an array of superconducting resonators is solved after the paper was published. In light of the developed technology in manipulating quantum information with superconducting circuit, one can couple other quantum oscillator system to superconducting resonators in order manipulation of its quantum states or parametric amplification of weak quantum signal. A theory that works for different coupling schemes has been studied in chapter 5. This will be a platform for further research.

2 GHz clock quantum key distribution over 260 km of standard telecom fiber.

PubMed

Wang, Shuang; Chen, Wei; Guo, Jun-Fu; Yin, Zhen-Qiang; Li, Hong-Wei; Zhou, Zheng; Guo, Guang-Can; Han, Zheng-Fu

2012-03-15

We report a demonstration of quantum key distribution (QKD) over a standard telecom fiber exceeding 50 dB in loss and 250 km in length. The differential phase shift QKD protocol was chosen and implemented with a 2 GHz system clock rate. By careful optimization of the 1 bit delayed Faraday-Michelson interferometer and the use of the superconducting single photon detector (SSPD), we achieved a quantum bit error rate below 2% when the fiber length was no more than 205 km, and of 3.45% for a 260 km fiber with 52.9 dB loss. We also improved the quantum efficiency of SSPD to obtain a high key rate for 50 km length.

Satellite laser ranging using superconducting nanowire single-photon detectors at 1064  nm wavelength.

PubMed

Xue, Li; Li, Zhulian; Zhang, Labao; Zhai, Dongsheng; Li, Yuqiang; Zhang, Sen; Li, Ming; Kang, Lin; Chen, Jian; Wu, Peiheng; Xiong, Yaoheng

2016-08-15

Satellite laser ranging operating at 1064 nm wavelength using superconducting nanowire single-photon detectors (SNSPDs) is successfully demonstrated. A SNSPD with an intrinsic quantum efficiency of 80% and a dark count rate of 100 cps at 1064 nm wavelength is developed and introduced to Yunnan Observatory in China. With improved closed-loop telescope systems (field of view of about 26^''), satellites including Cryosat, Ajisai, and Glonass with ranges of 1600 km, 3100 km, and 19,500 km, respectively, are experimentally ranged with mean echo rates of 1200/min, 4200/min, and 320/min, respectively. To the best of our knowledge, this is the first demonstration of laser ranging for satellites using SNSPDs at 1064 nm wavelength. Theoretical analysis of the detection efficiency and the mean echo rate for typical satellites indicate that it is possible for a SNSPD to range satellites from low Earth orbit to geostationary Earth orbit.

The Development of a Transition-Edge Hot-Electron Microbolometer for Observation of the Cosmic Microwave Background

NASA Astrophysics Data System (ADS)

Barrentine, Emily Margaret

In this thesis the development of a Transition-Edge Hot-Electron Microbolometer (THM) is presented. This detector will have the capacity to make sensitive and broadband astrophysical observations when deployed in large detector arrays in future ground- or space-based instruments, over frequencies ranging from 30-300 GHz (10-1 mm). This thesis focuses on the development of the THM for observations of the Cosmic Microwave Background (CMB), and specifically for observations of the CMB polarization signal. The THM is a micron-sized bolometer that is fabricated photolithographically. It consists of a superconducting Molybdenum/Gold Transition-Edge Sensor (TES) and a thin-film semi-metal Bismuth microwave absorber, both of which are deposited directly on the substrate. The THM employs the decoupling between electrons and phonons at low temperatures (˜100-300 mK) to provide thermal isolation for the bolometer. The devices are read out with Superconducting Quantum Interference Devices (SQUIDs). In this thesis a summary of the thermal and electrical models for the THM detector is presented. The physical processes within the detector, with particular attention to electron-phonon decoupling, and the lateral proximity effect between the superconducting leads and the TES, are also discussed. This understanding of the detector and these models are used to interpret measurements of thermal conductance, noise, responsivity and the transition behaviour of a variety of THM test devices. The optimization of the THM design, based on these models and measurements, is also discussed, and the thesis concludes with a presentation of the recommended THM design for CMB applications. In addition, a planar-microwave circuit design and a quasi-optical scheme for coupling microwave radiation to the THM detector are presented.

A Research and Development Strategy for Unexploded Ordnance Sensing

DTIC Science & Technology

1996-04-01

Each lane was carefully traversed with the MK-26 Ordnance Detector (dual fluxgate magnetometer hand-held unit) and the operator hand-excavated any...proton-precessing magnetometers , optically pumped magnetometers , fluxgates magnetometers , and magnetometers based on superconducting quantum...sensitivity better than 0.05 nT, and the optically-pumped magnetometers have sensitivity better than 0.005 nT. Fluxgate magnetometers are based on solid

Optimized Geometry for Superconducting Sensing Coils

NASA Technical Reports Server (NTRS)

Eom, Byeong Ho; Pananen, Konstantin; Hahn, Inseob

2008-01-01

An optimized geometry has been proposed for superconducting sensing coils that are used in conjunction with superconducting quantum interference devices (SQUIDs) in magnetic resonance imaging (MRI), magnetoencephalography (MEG), and related applications in which magnetic fields of small dipoles are detected. In designing a coil of this type, as in designing other sensing coils, one seeks to maximize the sensitivity of the detector of which the coil is a part, subject to geometric constraints arising from the proximity of other required equipment. In MRI or MEG, the main benefit of maximizing the sensitivity would be to enable minimization of measurement time. In general, to maximize the sensitivity of a detector based on a sensing coil coupled with a SQUID sensor, it is necessary to maximize the magnetic flux enclosed by the sensing coil while minimizing the self-inductance of this coil. Simply making the coil larger may increase its self-inductance and does not necessarily increase sensitivity because it also effectively increases the distance from the sample that contains the source of the signal that one seeks to detect. Additional constraints on the size and shape of the coil and on the distance from the sample arise from the fact that the sample is at room temperature but the coil and the SQUID sensor must be enclosed within a cryogenic shield to maintain superconductivity.

Provably secure and high-rate quantum key distribution with time-bin qudits

DOE PAGES

Islam, Nurul T.; Lim, Charles Ci Wen; Cahall, Clinton; ...

2017-11-24

The security of conventional cryptography systems is threatened in the forthcoming era of quantum computers. Quantum key distribution (QKD) features fundamentally proven security and offers a promising option for quantum-proof cryptography solution. Although prototype QKD systems over optical fiber have been demonstrated over the years, the key generation rates remain several orders of magnitude lower than current classical communication systems. In an effort toward a commercially viable QKD system with improved key generation rates, we developed a discrete-variable QKD system based on time-bin quantum photonic states that can generate provably secure cryptographic keys at megabit-per-second rates over metropolitan distances. Wemore » use high-dimensional quantum states that transmit more than one secret bit per received photon, alleviating detector saturation effects in the superconducting nanowire single-photon detectors used in our system that feature very high detection efficiency (of more than 70%) and low timing jitter (of less than 40 ps). Our system is constructed using commercial off-the-shelf components, and the adopted protocol can be readily extended to free-space quantum channels. In conclusion, the security analysis adopted to distill the keys ensures that the demonstrated protocol is robust against coherent attacks, finite-size effects, and a broad class of experimental imperfections identified in our system.« less

Provably secure and high-rate quantum key distribution with time-bin qudits

PubMed Central

Islam, Nurul T.; Lim, Charles Ci Wen; Cahall, Clinton; Kim, Jungsang; Gauthier, Daniel J.

2017-01-01

The security of conventional cryptography systems is threatened in the forthcoming era of quantum computers. Quantum key distribution (QKD) features fundamentally proven security and offers a promising option for quantum-proof cryptography solution. Although prototype QKD systems over optical fiber have been demonstrated over the years, the key generation rates remain several orders of magnitude lower than current classical communication systems. In an effort toward a commercially viable QKD system with improved key generation rates, we developed a discrete-variable QKD system based on time-bin quantum photonic states that can generate provably secure cryptographic keys at megabit-per-second rates over metropolitan distances. We use high-dimensional quantum states that transmit more than one secret bit per received photon, alleviating detector saturation effects in the superconducting nanowire single-photon detectors used in our system that feature very high detection efficiency (of more than 70%) and low timing jitter (of less than 40 ps). Our system is constructed using commercial off-the-shelf components, and the adopted protocol can be readily extended to free-space quantum channels. The security analysis adopted to distill the keys ensures that the demonstrated protocol is robust against coherent attacks, finite-size effects, and a broad class of experimental imperfections identified in our system. PMID:29202028

Provably secure and high-rate quantum key distribution with time-bin qudits.

PubMed

Islam, Nurul T; Lim, Charles Ci Wen; Cahall, Clinton; Kim, Jungsang; Gauthier, Daniel J

2017-11-01

The security of conventional cryptography systems is threatened in the forthcoming era of quantum computers. Quantum key distribution (QKD) features fundamentally proven security and offers a promising option for quantum-proof cryptography solution. Although prototype QKD systems over optical fiber have been demonstrated over the years, the key generation rates remain several orders of magnitude lower than current classical communication systems. In an effort toward a commercially viable QKD system with improved key generation rates, we developed a discrete-variable QKD system based on time-bin quantum photonic states that can generate provably secure cryptographic keys at megabit-per-second rates over metropolitan distances. We use high-dimensional quantum states that transmit more than one secret bit per received photon, alleviating detector saturation effects in the superconducting nanowire single-photon detectors used in our system that feature very high detection efficiency (of more than 70%) and low timing jitter (of less than 40 ps). Our system is constructed using commercial off-the-shelf components, and the adopted protocol can be readily extended to free-space quantum channels. The security analysis adopted to distill the keys ensures that the demonstrated protocol is robust against coherent attacks, finite-size effects, and a broad class of experimental imperfections identified in our system.

Provably secure and high-rate quantum key distribution with time-bin qudits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Islam, Nurul T.; Lim, Charles Ci Wen; Cahall, Clinton

The security of conventional cryptography systems is threatened in the forthcoming era of quantum computers. Quantum key distribution (QKD) features fundamentally proven security and offers a promising option for quantum-proof cryptography solution. Although prototype QKD systems over optical fiber have been demonstrated over the years, the key generation rates remain several orders of magnitude lower than current classical communication systems. In an effort toward a commercially viable QKD system with improved key generation rates, we developed a discrete-variable QKD system based on time-bin quantum photonic states that can generate provably secure cryptographic keys at megabit-per-second rates over metropolitan distances. Wemore » use high-dimensional quantum states that transmit more than one secret bit per received photon, alleviating detector saturation effects in the superconducting nanowire single-photon detectors used in our system that feature very high detection efficiency (of more than 70%) and low timing jitter (of less than 40 ps). Our system is constructed using commercial off-the-shelf components, and the adopted protocol can be readily extended to free-space quantum channels. In conclusion, the security analysis adopted to distill the keys ensures that the demonstrated protocol is robust against coherent attacks, finite-size effects, and a broad class of experimental imperfections identified in our system.« less

Towards a heralded eigenstate-preserving measurement of multi-qubit parity in circuit QED

NASA Astrophysics Data System (ADS)

Huembeli, Patrick; Nigg, Simon E.

2017-07-01

Eigenstate-preserving multi-qubit parity measurements lie at the heart of stabilizer quantum error correction, which is a promising approach to mitigate the problem of decoherence in quantum computers. In this work we explore a high-fidelity, eigenstate-preserving parity readout for superconducting qubits dispersively coupled to a microwave resonator, where the parity bit is encoded in the amplitude of a coherent state of the resonator. Detecting photons emitted by the resonator via a current biased Josephson junction yields information about the parity bit. We analyze theoretically the measurement back action in the limit of a strongly coupled fast detector and show that in general such a parity measurement, while approximately quantum nondemolition is not eigenstate preserving. To remediate this shortcoming we propose a simple dynamical decoupling technique during photon detection, which greatly reduces decoherence within a given parity subspace. Furthermore, by applying a sequence of fast displacement operations interleaved with the dynamical decoupling pulses, the natural bias of this binary detector can be efficiently suppressed. Finally, we introduce the concept of a heralded parity measurement, where a detector click guarantees successful multi-qubit parity detection even for finite detection efficiency.

Efficient generation of twin photons at telecom wavelengths with 2.5 GHz repetition-rate-tunable comb laser.

PubMed

Jin, Rui-Bo; Shimizu, Ryosuke; Morohashi, Isao; Wakui, Kentaro; Takeoka, Masahiro; Izumi, Shuro; Sakamoto, Takahide; Fujiwara, Mikio; Yamashita, Taro; Miki, Shigehito; Terai, Hirotaka; Wang, Zhen; Sasaki, Masahide

2014-12-19

Efficient generation and detection of indistinguishable twin photons are at the core of quantum information and communications technology (Q-ICT). These photons are conventionally generated by spontaneous parametric down conversion (SPDC), which is a probabilistic process, and hence occurs at a limited rate, which restricts wider applications of Q-ICT. To increase the rate, one had to excite SPDC by higher pump power, while it inevitably produced more unwanted multi-photon components, harmfully degrading quantum interference visibility. Here we solve this problem by using recently developed 10 GHz repetition-rate-tunable comb laser, combined with a group-velocity-matched nonlinear crystal, and superconducting nanowire single photon detectors. They operate at telecom wavelengths more efficiently with less noises than conventional schemes, those typically operate at visible and near infrared wavelengths generated by a 76 MHz Ti Sapphire laser and detected by Si detectors. We could show high interference visibilities, which are free from the pump-power induced degradation. Our laser, nonlinear crystal, and detectors constitute a powerful tool box, which will pave a way to implementing quantum photonics circuits with variety of good and low-cost telecom components, and will eventually realize scalable Q-ICT in optical infra-structures.

Microwave photonics with superconducting quantum circuits

NASA Astrophysics Data System (ADS)

Gu, Xiu; Kockum, Anton Frisk; Miranowicz, Adam; Liu, Yu-xi; Nori, Franco

2017-11-01

In the past 20 years, impressive progress has been made both experimentally and theoretically in superconducting quantum circuits, which provide a platform for manipulating microwave photons. This emerging field of superconducting quantum microwave circuits has been driven by many new interesting phenomena in microwave photonics and quantum information processing. For instance, the interaction between superconducting quantum circuits and single microwave photons can reach the regimes of strong, ultra-strong, and even deep-strong coupling. Many higher-order effects, unusual and less familiar in traditional cavity quantum electrodynamics with natural atoms, have been experimentally observed, e.g., giant Kerr effects, multi-photon processes, and single-atom induced bistability of microwave photons. These developments may lead to improved understanding of the counterintuitive properties of quantum mechanics, and speed up applications ranging from microwave photonics to superconducting quantum information processing. In this article, we review experimental and theoretical progress in microwave photonics with superconducting quantum circuits. We hope that this global review can provide a useful roadmap for this rapidly developing field.

Superconducting transmission line particle detector

DOEpatents

Gray, K.E.

1988-07-28

A microvertex particle detector for use in a high energy physic collider including a plurality of parallel superconducting thin film strips separated from a superconducting ground plane by an insulating layer to form a plurality of superconducting waveguides. The microvertex particle detector indicates passage of a charged subatomic particle by measuring a voltage pulse measured across a superconducting waveguide caused by the transition of the superconducting thin film strip from a superconducting to a non- superconducting state in response to the passage of a charged particle. A plurality of superconducting thin film strips in two orthogonal planes plus the slow electromagnetic wave propagating in a superconducting transmission line are used to resolve N/sup 2/ ambiguity of charged particle events. 6 figs.

Superconducting transmission line particle detector

DOEpatents

Gray, Kenneth E.

1989-01-01

A microvertex particle detector for use in a high energy physic collider including a plurality of parallel superconducting thin film strips separated from a superconducting ground plane by an insulating layer to form a plurality of superconducting waveguides. The microvertex particle detector indicates passage of a charged subatomic particle by measuring a voltage pulse measured across a superconducting waveguide caused by the transition of the superconducting thin film strip from a superconducting to a non-superconducting state in response to the passage of a charged particle. A plurality of superconducting thin film strips in two orthogonal planes plus the slow electromagnetic wave propogating in a superconducting transmission line are used to resolve N.sup.2 ambiguity of charged particle events.

Hidden magnetism and quantum criticality in the heavy fermion superconductor CeRhIn5.

PubMed

Park, Tuson; Ronning, F; Yuan, H Q; Salamon, M B; Movshovich, R; Sarrao, J L; Thompson, J D

2006-03-02

With only a few exceptions that are well understood, conventional superconductivity does not coexist with long-range magnetic order (for example, ref. 1). Unconventional superconductivity, on the other hand, develops near a phase boundary separating magnetically ordered and magnetically disordered phases. A maximum in the superconducting transition temperature T(c) develops where this boundary extrapolates to zero Kelvin, suggesting that fluctuations associated with this magnetic quantum-critical point are essential for unconventional superconductivity. Invariably, though, unconventional superconductivity masks the magnetic phase boundary when T < T(c), preventing proof of a magnetic quantum-critical point. Here we report specific-heat measurements of the pressure-tuned unconventional superconductor CeRhIn5 in which we find a line of quantum-phase transitions induced inside the superconducting state by an applied magnetic field. This quantum-critical line separates a phase of coexisting antiferromagnetism and superconductivity from a purely unconventional superconducting phase, and terminates at a quantum tetracritical point where the magnetic field completely suppresses superconductivity. The T --> 0 K magnetic field-pressure phase diagram of CeRhIn5 is well described with a theoretical model developed to explain field-induced magnetism in the high-T(c) copper oxides, but in which a clear delineation of quantum-phase boundaries has not been possible. These experiments establish a common relationship among hidden magnetism, quantum criticality and unconventional superconductivity in copper oxides and heavy-electron systems such as CeRhIn5.

Continuous high speed coherent one-way quantum key distribution.

PubMed

Stucki, Damien; Barreiro, Claudio; Fasel, Sylvain; Gautier, Jean-Daniel; Gay, Olivier; Gisin, Nicolas; Thew, Rob; Thoma, Yann; Trinkler, Patrick; Vannel, Fabien; Zbinden, Hugo

2009-08-03

Quantum key distribution (QKD) is the first commercial quantum technology operating at the level of single quanta and is a leading light for quantum-enabled photonic technologies. However, controlling these quantum optical systems in real world environments presents significant challenges. For the first time, we have brought together three key concepts for future QKD systems: a simple high-speed protocol; high performance detection; and integration both, at the component level and for standard fibre network connectivity. The QKD system is capable of continuous and autonomous operation, generating secret keys in real time. Laboratory and field tests were performed and comparisons made with robust InGaAs avalanche photodiodes and superconducting detectors. We report the first real world implementation of a fully functional QKD system over a 43 dB-loss (150 km) transmission line in the Swisscom fibre optic network where we obtained average real-time distribution rates over 3 hours of 2.5 bps.

Development and study of charge sensors for fast charge detection in quantum dots

NASA Astrophysics Data System (ADS)

Thalakulam, Madhu

Charge detection at microsecond time-scales has far reaching consequences in both technology and in our understanding of electron dynamics in nanoscale devices such as quantum dots. Radio-frequency superconducting single electron transistors (RF-SET) and quantum point contacts (QPC) are ultra sensitive charge sensors operating near the quantum limit. The operation of RF-SETs outside the superconducting gap has been a topic of study; the sub-gap operation, especially in the presence of large quantum fluctuations of quasiparticles remains largely unexplored, both theoretically and experimentally. We have investigated the effects of quantum fluctuations of quasiparticles on the operation of RF-SETs for large values of the quasiparticle cotunneling parameter alpha = 8EJ/Ec, where EJ and Ec are the Josephson and charging energies. We find that, for alpha > 1, sub-gap RF-SET operation is still feasible despite quantum fluctuations that wash out quasiparticle tunneling thresholds. Such RF-SETs show linearity and signal-to-noise ratio superior to those obtained when quantum fluctuations are weak, while still demonstrating excellent charge sensitivity. We have operated a QPC charge detector in a radio frequency mode that allows fast charge detection in a bandwidth of several megahertz. The noise limiting the sensitivity of the charge detector is not the noise of a secondary amplifier, but the non-equilibrium device noise of the QPC itself. The noise power averaged over a measurement bandwidth of about 10MHz around the carrier frequency is in agreement with the theory of photon-assisted shot noise. Frequency-resolved measurements, however show several significant discrepancies with the theoretical predictions. The measurement techniques developed can also be used to investigate the noise of other semiconductor nanostructures such as quantum dots in the Kondo regime. A study of the noise characteristics alone can not determine whether the device is operating at the quantum limit; a characterization of back action is also necessary. The inelastic current through a double quantum dot system (DQD) is sensitive to the spectral density of voltage fluctuations in its electromagnetic environment. Electrical transport studies on a DQD system electrostatically coupled to an SET shows qualitative evidence of back-action of SET. The design and fabrication of a few electron DQD device with integrated RF-SET and QPC charge sensors for the study of back action of the sensors and real-time electron dynamics in the DQD are also discussed.

SQUID readout and ultra-low magnetic fields for Gravity Probe-B (GP-B)

NASA Technical Reports Server (NTRS)

Lockhart, James M.

1986-01-01

The superconducting readout system to be used for resolving 0.001 arcsec changes in the gyroscope spin direction in the Relativity Gyroscope (GP-B) experiment is described. This system couples the London magnetic moment flux of the spinning gyro to a low noise superconducting quantum interference device (SQUID) detector. Resolution limits and noise performance of the detection system are discussed, and improvements obtained and expected with advanced SQUIDs are presented. Also described is the novel use of superconducting magnetic shielding techniques to obtain a 250 dB attenuation of the earth's magnetic field at the location of the gyroscopes. In this approach, expanded superconducting foil shields are coupled with fixed cylindrical superconducting shields and special geometric considerations to obtain the extremely high attenuation factor required. With these shielding techniques, it appears that the 0.5-Gauss earth field (which appears to the gyroscopes as an ac field at the satellite roll rate) can be reduced to the 10 to the -13th G level required by the experiment. Recent results concerning improvements in the performance of the superconducting foil techniques obtained with the use of a new computer-controlled cooling system are presented.

Enhancements to a Superconducting Quantum Interference Device (SQUID) Multiplexer Readout and Control System

NASA Technical Reports Server (NTRS)

Forgione, J.; Benford, D. J.; Buchanan, E. D.; Moseley, S. H.; Rebar, J.; Shafer, R. A.

2004-01-01

Far-infrared detector arrays such as the 16x32 superconducting bolometer array for the SAFIRE instrument (flying on the SOFIA airborne observatory) require systems of readout and control electronics to provide translation between a user-driven, digital PC and the cold, analog world of the cryogenic detector. In 2001, the National Institute of Standards and Technology (NIST) developed their Mark III electronics for purposes of control and readout of their 1x32 SQUID Multiplexer chips. We at NASA s Goddard Space Flight Center acquired a Mark 111 system and subsequently designed upgrades to suit our and our collaborators purposes. We developed an arbitrary, programmable multiplexing system that allows the user to cycle through rows in a SQUID array in an infinite number of combinations. We provided hooks in the Mark III system to allow readout of signals from outside the Mark 111 system, such as telescope status information. Finally, we augmented the heart of the system with a new feedback algorithm implementation, flexible diagnostic tools, and informative telemetry.

Enhancements to a superconducting quantum interference device (SQUID) multiplexer readout and control system

NASA Astrophysics Data System (ADS)

Forgione, Joshua B.; Benford, Dominic J.; Buchanan, Ernest D.; Moseley, S. H., Jr.; Rebar, Joyce; Shafer, Richard A.

2004-10-01

Far-infrared detector arrays such as the 16x32 superconducting bolometer array for the SAFIRE instrument (flying on the SOFIA airborne observatory) require systems of readout and control electronics to provide translation between a user-driven, digital PC and the cold, analog world of the cryogenic detector. In 2001, the National Institute of Standards and Technology (NIST) developed their Mark III electronics for purposes of control and readout of their 1x32 SQUID Multiplexer chips. We at NASA's Goddard Space Flight Center acquired a Mark III system and subsequently designed upgrades to suit our and our collaborators' purposes. We developed an arbitrary, programmable multiplexing system that allows the user to cycle through rows in a SQUID array in an infinite number of combinations. We provided 'hooks' in the Mark III system to allow readout of signals from outside the Mark III system, such as telescope status information. Finally, we augmented the heart of the system with a new feedback algorithm implementation, flexible diagnostic tools, and informative telemetry.

Superconducting transmission line particle detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gray, K.E.

This paper describes a microvertex particle detector for use in a high energy physic collider including a plurality of parallel superconducting thin film strips separated from a superconducting ground plane by an insulating layer to form a plurality of superconducting waveguides. The microvertex particle detector indicates passage of a charged subatomic particle by measuring a voltage pulse measured across a superconducting waveguide caused by the transition of the superconducting thin film strip from a superconducting to a non-superconducting state in response to the passage of a charged particle. A plurality of superconducting thin film strips in two orthogonal planes plusmore » the slow electromagnetic wave propogating in a superconducting transmission line are used to resolve N{sup 2} ambiguity of charged particle events.« less

Superconducting transmission line particle detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gray, K.E.

A microvertex particle detector for use in a high energy physic collider including a plurality of parallel superconducting thin film strips separated from a superconducting ground plane by an insulating layer to form a plurality of superconducting waveguides. The microvertex particle detector indicates passage of a charged subatomic particle by measuring a voltage pulse measured across a superconducting waveguide caused by the transition of the superconducting thin film strip from a superconducting to a non- superconducting state in response to the passage of a charged particle. A plurality of superconducting thin film strips in two orthogonal planes plus the slowmore » electromagnetic wave propagating in a superconducting transmission line are used to resolve N/sup 2/ ambiguity of charged particle events. 6 figs.« less

Efficient generation of twin photons at telecom wavelengths with 2.5 GHz repetition-rate-tunable comb laser

PubMed Central

Jin, Rui-Bo; Shimizu, Ryosuke; Morohashi, Isao; Wakui, Kentaro; Takeoka, Masahiro; Izumi, Shuro; Sakamoto, Takahide; Fujiwara, Mikio; Yamashita, Taro; Miki, Shigehito; Terai, Hirotaka; Wang, Zhen; Sasaki, Masahide

2014-01-01

Efficient generation and detection of indistinguishable twin photons are at the core of quantum information and communications technology (Q-ICT). These photons are conventionally generated by spontaneous parametric down conversion (SPDC), which is a probabilistic process, and hence occurs at a limited rate, which restricts wider applications of Q-ICT. To increase the rate, one had to excite SPDC by higher pump power, while it inevitably produced more unwanted multi-photon components, harmfully degrading quantum interference visibility. Here we solve this problem by using recently developed 10 GHz repetition-rate-tunable comb laser, combined with a group-velocity-matched nonlinear crystal, and superconducting nanowire single photon detectors. They operate at telecom wavelengths more efficiently with less noises than conventional schemes, those typically operate at visible and near infrared wavelengths generated by a 76 MHz Ti Sapphire laser and detected by Si detectors. We could show high interference visibilities, which are free from the pump-power induced degradation. Our laser, nonlinear crystal, and detectors constitute a powerful tool box, which will pave a way to implementing quantum photonics circuits with variety of good and low-cost telecom components, and will eventually realize scalable Q-ICT in optical infra-structures. PMID:25524646

High-Resolution Hard X-Ray and Gamma-Ray Spectrometers Based on Superconducting Absorbers Coupled to Superconducting Transition Edge Sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

van den Berg, M.; Chow, D.; Loshak, A.

2000-09-21

We are developing detectors based on bulk superconducting absorbers coupled to superconducting transition edge sensors (TES) for high-resolution spectroscopy of hard X-rays and soft gamma-rays. We have achieved an energy resolution of 70 eV FWHM at 60 keV using a 1 x 1 x 0.25 mm{sup 3} Sn absorber coupled to a Mo/Cu multilayer TES with a transition temperature of 100 mK. The response of the detector is compared with a simple model using only material properties data and characteristics derived from IV-measurements. We have also manufactured detectors using superconducting absorbers with a higher stopping power, such as Pb andmore » Ta. We present our first measurements of these detectors, including the thermalization characteristics of the bulk superconducting absorbers. The differences in performance between the detectors are discussed and an outline of the future direction of our detector development efforts is given.« less

NMR/MRI with hyperpolarized gas and high Tc SQUID

DOEpatents

Schlenga, Klaus; de Souza, Ricardo E.; Wong-Foy, Annjoe; Clarke, John; Pines, Alexander

2000-01-01

A method and apparatus for the detection of nuclear magnetic resonance (NMR) signals and production of magnetic resonance imaging (MRI) from samples combines the use of hyperpolarized inert gases to enhance the NMR signals from target nuclei in a sample and a high critical temperature (Tc) superconducting quantum interference device (SQUID) to detect the NMR signals. The system operates in static magnetic fields of 3 mT or less (down to 0.1 mT), and at temperatures from liquid nitrogen (77K) to room temperature. Sample size is limited only by the size of the magnetic field coils and not by the detector. The detector is a high Tc SQUID magnetometer designed so that the SQUID detector can be very close to the sample, which can be at room temperature.

Superconducting Digital Multiplexers for Sensor Arrays

NASA Technical Reports Server (NTRS)

Kadin, Alan M.; Brock, Darren K.; Gupta, Deepnarayan

2004-01-01

Arrays of cryogenic microbolometers and other cryogenic detectors are being developed for infrared imaging. If the signal from each sensor is amplified, multiplexed, and digitized using superconducting electronics, then this data can be efficiently read out to ambient temperature with a minimum of noise and thermal load. HYPRES is developing an integrated system based on SQUID amplifiers, a high-resolution analog-to-digital converter (ADC) based on RSFQ (rapid single flux quantum) logic, and a clocked RSFQ multiplexer. The ADC and SQUIDs have already been demonstrated for other projects, so this paper will focus on new results of a digital multiplexer. Several test circuits have been fabricated using Nb Josephson technology and are about to be tested at T = 4.2 K, with a more complete prototype in preparation.

Collective coupling in hybrid superconducting circuits

NASA Astrophysics Data System (ADS)

Saito, Shiro

Hybrid quantum systems utilizing superconducting circuits have attracted significant recent attention, not only for quantum information processing tasks but also as a way to explore fundamentally new physics regimes. In this talk, I will discuss two superconducting circuit based hybrid quantum system approaches. The first is a superconducting flux qubit - electron spin ensemble hybrid system in which quantum information manipulated in the flux qubit can be transferred to, stored in and retrieved from the ensemble. Although the coherence time of the ensemble is short, about 20 ns, this is a significant first step to utilize the spin ensemble as quantum memory for superconducting flux qubits. The second approach is a superconducting resonator - flux qubit ensemble hybrid system in which we fabricated a superconducting LC resonator coupled to a large ensemble of flux qubits. Here we observed a dispersive frequency shift of approximately 250 MHz in the resonators transmission spectrum. This indicates thousands of flux qubits are coupling to the resonator collectively. Although we need to improve our qubits inhomogeneity, our system has many potential uses including the creation of new quantum metamaterials, novel applications in quantum metrology and so on. This work was partially supported by JSPS KAKENHI Grant Number 25220601.

Resolving the vacuum fluctuations of an optomechanical system using an artificial atom

NASA Astrophysics Data System (ADS)

Lecocq, F.; Teufel, J. D.; Aumentado, J.; Simmonds, R. W.

2015-08-01

Heisenberg’s uncertainty principle results in one of the strangest quantum behaviours: a mechanical oscillator can never truly be at rest. Even at a temperature of absolute zero, its position and momentum are still subject to quantum fluctuations. However, direct energy detection of the oscillator in its ground state makes it seem motionless, and in linear position measurements detector noise can masquerade as mechanical fluctuations. Thus, how can we resolve quantum fluctuations? Here, we parametrically couple a micromechanical oscillator to a microwave cavity to prepare the system in its quantum ground state and then amplify the remaining vacuum fluctuations into real energy quanta. We monitor the photon/phonon-number distributions using a superconducting qubit, allowing us to resolve the quantum vacuum fluctuations of the macroscopic oscillator’s motion. Our results further demonstrate the ability to control a long-lived mechanical oscillator using a non-Gaussian resource, directly enabling applications in quantum information processing and enhanced detection of displacement and forces.

Investigations of a voltage-biased microwave cavity for quantum measurements of nanomechanical resonators

NASA Astrophysics Data System (ADS)

Rouxinol, Francisco; Hao, Hugo; Lahaye, Matt

2015-03-01

Quantum electromechanical systems incorporating superconducting qubits have received extensive interest in recent years due to their promising prospects for studying fundamental topics of quantum mechanics such as quantum measurement, entanglement and decoherence in new macroscopic limits, also for their potential as elements in technological applications in quantum information network and weak force detector, to name a few. In this presentation we will discuss ours efforts toward to devise an electromechanical circuit to strongly couple a nanomechanical resonator to a superconductor qubit, where a high voltage dc-bias is required, to study quantum behavior of a mechanical resonator. Preliminary results of our latest generation of devices integrating a superconductor qubit into a high-Q voltage biased microwave cavities are presented. Developments in the circuit design to couple a mechanical resonator to a qubit in the high-Q voltage bias CPW cavity is discussed as well prospects of achieving single-phonon measurement resolution. National Science Foundation under Grant No. DMR-1056423 and Grant No. DMR-1312421.

Remote NMR/MRI detection of laser polarized gases

DOEpatents

Pines, Alexander; Saxena, Sunil; Moule, Adam; Spence, Megan; Seeley, Juliette A.; Pierce, Kimberly L.; Han, Song-I; Granwehr, Josef

2006-06-13

An apparatus and method for remote NMR/MRI spectroscopy having an encoding coil with a sample chamber, a supply of signal carriers, preferably hyperpolarized xenon and a detector allowing the spatial and temporal separation of signal preparation and signal detection steps. This separation allows the physical conditions and methods of the encoding and detection steps to be optimized independently. The encoding of the carrier molecules may take place in a high or a low magnetic field and conventional NMR pulse sequences can be split between encoding and detection steps. In one embodiment, the detector is a high magnetic field NMR apparatus. In another embodiment, the detector is a superconducting quantum interference device. A further embodiment uses optical detection of Rb--Xe spin exchange. Another embodiment uses an optical magnetometer using non-linear Faraday rotation. Concentration of the signal carriers in the detector can greatly improve the signal to noise ratio.

High-speed wavelength-division multiplexing quantum key distribution system.

PubMed

Yoshino, Ken-ichiro; Fujiwara, Mikio; Tanaka, Akihiro; Takahashi, Seigo; Nambu, Yoshihiro; Tomita, Akihisa; Miki, Shigehito; Yamashita, Taro; Wang, Zhen; Sasaki, Masahide; Tajima, Akio

2012-01-15

A high-speed quantum key distribution system was developed with the wavelength-division multiplexing (WDM) technique and dedicated key distillation hardware engines. Two interferometers for encoding and decoding are shared over eight wavelengths to reduce the system's size, cost, and control complexity. The key distillation engines can process a huge amount of data from the WDM channels by using a 1 Mbit block in real time. We demonstrated a three-channel WDM system that simultaneously uses avalanche photodiodes and superconducting single-photon detectors. We achieved 12 h continuous key generation with a secure key rate of 208 kilobits per second through a 45 km field fiber with 14.5 dB loss.

Qubit lattice coherence induced by electromagnetic pulses in superconducting metamaterials.

PubMed

Ivić, Z; Lazarides, N; Tsironis, G P

2016-07-12

Quantum bits (qubits) are at the heart of quantum information processing schemes. Currently, solid-state qubits, and in particular the superconducting ones, seem to satisfy the requirements for being the building blocks of viable quantum computers, since they exhibit relatively long coherence times, extremely low dissipation, and scalability. The possibility of achieving quantum coherence in macroscopic circuits comprising Josephson junctions, envisioned by Legett in the 1980's, was demonstrated for the first time in a charge qubit; since then, the exploitation of macroscopic quantum effects in low-capacitance Josephson junction circuits allowed for the realization of several kinds of superconducting qubits. Furthermore, coupling between qubits has been successfully achieved that was followed by the construction of multiple-qubit logic gates and the implementation of several algorithms. Here it is demonstrated that induced qubit lattice coherence as well as two remarkable quantum coherent optical phenomena, i.e., self-induced transparency and Dicke-type superradiance, may occur during light-pulse propagation in quantum metamaterials comprising superconducting charge qubits. The generated qubit lattice pulse forms a compound "quantum breather" that propagates in synchrony with the electromagnetic pulse. The experimental confirmation of such effects in superconducting quantum metamaterials may open a new pathway to potentially powerful quantum computing.

Observation of enhanced superconductivity in the vicinity of Ar-induced nano-cavities in Pb(111).

PubMed

Song, Sang Yong; Seo, Jungpil

2017-09-22

Local variations of superconductivity have been studied using scanning tunneling microscopy around nano-cavities formed by Ar ions embedded in Pb(111). Various factors including the density of states at Fermi energy, electron-phonon couplings, and quantum well states, which are known to affect superconductivity, have been examined. We show that the superconductivity is enhanced near the nano-cavities and propose that quantum effects such as quantum confinement, proximity effect and multi-gap effect are possibly involved in determining the superconducting gap of this system. These results have important implications for the characterization and understanding of superconductivity at a nanometer scale.

Simultaneous readout of 128 X-ray and gamma-ray transition-edge microcalorimeters using microwave SQUID multiplexing

NASA Astrophysics Data System (ADS)

Mates, J. A. B.; Becker, D. T.; Bennett, D. A.; Dober, B. J.; Gard, J. D.; Hays-Wehle, J. P.; Fowler, J. W.; Hilton, G. C.; Reintsema, C. D.; Schmidt, D. R.; Swetz, D. S.; Vale, L. R.; Ullom, J. N.

2017-08-01

The number of elements in most cryogenic sensor arrays is limited by the technology available to multiplex signals from the arrays into a smaller number of wires and readout amplifiers. The largest demonstrated arrays of transition-edge sensor (TES) microcalorimeters contain roughly 250 detectors and use time-division multiplexing with Superconducting Quantum Interference Devices (SQUIDs). The bandwidth limits of this technology constrain the number of sensors per amplifier chain, a quantity known as the multiplexing factor, to several 10s. With microwave SQUID multiplexing, we can expand the readout bandwidth and enable much larger multiplexing factors. While microwave SQUID multiplexing of TES microcalorimeters has been previously demonstrated with small numbers of detectors, we now present a fully scalable demonstration in which 128 TES detectors are read out on a single pair of coaxial cables.

A modified Stern-Gerlach experiment using a quantum two-state magnetic field

NASA Astrophysics Data System (ADS)

Daghigh, Ramin G.; Green, Michael D.; West, Christopher J.

2018-06-01

The Stern-Gerlach experiment has played an important role in our understanding of quantum behavior. We propose and analyze a modified version of this experiment where the magnetic field of the detector is in a quantum superposition, which may be experimentally realized using a superconducting flux qubit. We show that if incident spin-1/2 particles couple with the two-state magnetic field, a discrete target distribution results that resembles the distribution in the classical Stern-Gerlach experiment. As an application of the general result, we compute the distribution for a Gaussian waveform of the incident fermion. This analysis allows us to demonstrate theoretically: (1) the quantization of the intrinsic angular momentum of a spin-1/2 particle, and (2) a correlation between EPR pairs leading to nonlocality, without necessarily collapsing the particle's spin wavefunction.

Fiber-coupled superconducting nanowire single-photon detectors integrated with a bandpass filter on the fiber end-face

NASA Astrophysics Data System (ADS)

Zhang, W. J.; Yang, X. Y.; Li, H.; You, L. X.; Lv, C. L.; Zhang, L.; Zhang, C. J.; Liu, X. Y.; Wang, Z.; Xie, X. M.

2018-07-01

Superconducting nanowire single-photon detectors (SNSPDs) with both high system detection efficiency (SDE) and low dark count rate (DCR) play significant roles in quantum information processes and various applications. The background dark counts of SNSPDs originate from the room temperature blackbody radiation coupled to the device via a fiber. Therefore, a bandpass filter (BPF) operated at low temperature with minimal insert loss is necessary to suppress the background DCR. Herein, a low-loss BPF integrated on a single-mode fiber end-face was designed, fabricated and verified for the low temperature implement. The fiber end-face BPF was featured with a typical passband width about 40 nm in the 1550 nm telecom band and a peak transmittance of over 0.98. SNSPD with high SDE fabricated on a distributed Bragg reflector was coupled to the BPF. The device with such a BPF showed an SDE of 80% at a DCR of 0.5 Hz, measured at 2.1 K. Compared the same device without a BPF, the DCR was reduced by over 13 dB with an SDE decrease of <3%.

Superconducting nanoribbon with a constriction: A quantum-confined Josephson junction

NASA Astrophysics Data System (ADS)

Flammia, L.; Zhang, L.-F.; Covaci, L.; Perali, A.; Milošević, M. V.

2018-04-01

Extended defects are known to strongly affect nanoscale superconductors. Here, we report the properties of superconducting nanoribbons with a constriction formed between two adjacent step edges by solving the Bogoliubov-de Gennes equations self-consistently in the regime where quantum confinement is important. Since the quantum resonances of the superconducting gap in the constricted area are different from the rest of the nanoribbon, such constriction forms a quantum-confined S-S'-S Josephson junction, with a broadly tunable performance depending on the length and width of the constriction with respect to the nanoribbon, and possible gating. These findings provide an intriguing approach to further tailor superconducting quantum devices where Josephson effect is of use.

Quantum Devices Bonded Beneath a Superconducting Shield: Part 2

NASA Astrophysics Data System (ADS)

McRae, Corey Rae; Abdallah, Adel; Bejanin, Jeremy; Earnest, Carolyn; McConkey, Thomas; Pagel, Zachary; Mariantoni, Matteo

The next-generation quantum computer will rely on physical quantum bits (qubits) organized into arrays to form error-robust logical qubits. In the superconducting quantum circuit implementation, this architecture will require the use of larger and larger chip sizes. In order for on-chip superconducting quantum computers to be scalable, various issues found in large chips must be addressed, including the suppression of box modes (due to the sample holder) and the suppression of slot modes (due to fractured ground planes). By bonding a metallized shield layer over a superconducting circuit using thin-film indium as a bonding agent, we have demonstrated proof of concept of an extensible circuit architecture that holds the key to the suppression of spurious modes. Microwave characterization of shielded transmission lines and measurement of superconducting resonators were compared to identical unshielded devices. The elimination of box modes was investigated, as well as bond characteristics including bond homogeneity and the presence of a superconducting connection.

Metallic Contaminant Detection using a High-Temperature Superconducting Quantum Interference Devices Gradiometer

NASA Astrophysics Data System (ADS)

Saburo, Tanaka; Tomohiro, Akai; Makoto, Takemoto; Yoshimi, Hatsukade; Takeyoshi, Ohtani; Yoshio, Ikeda; Shuichi, Suzuki

2010-08-01

We develop magnetic metallic contaminant detectors using high-temperature superconducting quantum interference devices (HTS-SQUIDs) for industrial products. Finding ultra-small metallic contaminants is an important issue for manufacturers producing commercial products such as lithium ion batteries. If such contaminants cause damages, the manufacturer of the product suffers a big financial loss due to having to recall the faulty products. Previously, we described a system for finding such ultra-small particles in food. In this study, we describe further developments of the system, for the reduction of the effect of the remnant field of the products, and we test the parallel magnetization of the products to generate the remnant field only at both ends of the products. In addition, we use an SQUID gradiometer in place of the magnetometer to reduce the edge effect by measuring the magnetic field gradient. We test the performances of the system and find that tiny iron particles as small as 50 × 50 μm2 on the electrode of a lithium ion battery could be clearly detected. This detection level is difficult to achieve when using other methods.

Superconducting Detectors for Study of Infant Universe

NASA Image and Video Library

2014-03-17

The BICEP2 telescope at the South Pole used a specialized array of superconducting detectors to capture polarized light from billions of years ago. The detector array is shown here, under a microscope.

Qubit lattice coherence induced by electromagnetic pulses in superconducting metamaterials

PubMed Central

Ivić, Z.; Lazarides, N.; Tsironis, G. P.

2016-01-01

Quantum bits (qubits) are at the heart of quantum information processing schemes. Currently, solid-state qubits, and in particular the superconducting ones, seem to satisfy the requirements for being the building blocks of viable quantum computers, since they exhibit relatively long coherence times, extremely low dissipation, and scalability. The possibility of achieving quantum coherence in macroscopic circuits comprising Josephson junctions, envisioned by Legett in the 1980’s, was demonstrated for the first time in a charge qubit; since then, the exploitation of macroscopic quantum effects in low-capacitance Josephson junction circuits allowed for the realization of several kinds of superconducting qubits. Furthermore, coupling between qubits has been successfully achieved that was followed by the construction of multiple-qubit logic gates and the implementation of several algorithms. Here it is demonstrated that induced qubit lattice coherence as well as two remarkable quantum coherent optical phenomena, i.e., self-induced transparency and Dicke-type superradiance, may occur during light-pulse propagation in quantum metamaterials comprising superconducting charge qubits. The generated qubit lattice pulse forms a compound ”quantum breather” that propagates in synchrony with the electromagnetic pulse. The experimental confirmation of such effects in superconducting quantum metamaterials may open a new pathway to potentially powerful quantum computing. PMID:27403780

Qubit lattice coherence induced by electromagnetic pulses in superconducting metamaterials

NASA Astrophysics Data System (ADS)

Ivić, Z.; Lazarides, N.; Tsironis, G. P.

2016-07-01

Quantum bits (qubits) are at the heart of quantum information processing schemes. Currently, solid-state qubits, and in particular the superconducting ones, seem to satisfy the requirements for being the building blocks of viable quantum computers, since they exhibit relatively long coherence times, extremely low dissipation, and scalability. The possibility of achieving quantum coherence in macroscopic circuits comprising Josephson junctions, envisioned by Legett in the 1980’s, was demonstrated for the first time in a charge qubit; since then, the exploitation of macroscopic quantum effects in low-capacitance Josephson junction circuits allowed for the realization of several kinds of superconducting qubits. Furthermore, coupling between qubits has been successfully achieved that was followed by the construction of multiple-qubit logic gates and the implementation of several algorithms. Here it is demonstrated that induced qubit lattice coherence as well as two remarkable quantum coherent optical phenomena, i.e., self-induced transparency and Dicke-type superradiance, may occur during light-pulse propagation in quantum metamaterials comprising superconducting charge qubits. The generated qubit lattice pulse forms a compound ”quantum breather” that propagates in synchrony with the electromagnetic pulse. The experimental confirmation of such effects in superconducting quantum metamaterials may open a new pathway to potentially powerful quantum computing.

Superconductivity in epitaxially grown self-assembled indium islands: progress towards hybrid superconductor/semiconductor optical sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gehl, Michael; Gibson, Ricky; Zandbergen, Sander

Currently, superconducting qubits lead the way in potential candidates for quantum computing. This is a result of the robust nature of superconductivity and the non-linear Josephson effect which make possible many types of qubits. At the same time, transferring quantum information over long distances typically relies on the use of photons as the elementary qubit. Converting between stationary electronic qubits in superconducting systems and traveling photonic qubits is a challenging yet necessary goal for the interface of quantum computing and communication. The most promising path to achieving this goal appears to be the integration of superconductivity with optically active semiconductors,more » with quantum information being transferred between the two by means of the superconducting proximity effect. Obtaining good interfaces between superconductor and semiconductor is the next obvious step for improving these hybrid systems. As a result, we report on our observation of superconductivity in self-assembled indium structures grown epitaxially on the surface of semiconductor material.« less

Superconductivity in epitaxially grown self-assembled indium islands: progress towards hybrid superconductor/semiconductor optical sources

DOE PAGES

Gehl, Michael; Gibson, Ricky; Zandbergen, Sander; ...

2016-02-01

Currently, superconducting qubits lead the way in potential candidates for quantum computing. This is a result of the robust nature of superconductivity and the non-linear Josephson effect which make possible many types of qubits. At the same time, transferring quantum information over long distances typically relies on the use of photons as the elementary qubit. Converting between stationary electronic qubits in superconducting systems and traveling photonic qubits is a challenging yet necessary goal for the interface of quantum computing and communication. The most promising path to achieving this goal appears to be the integration of superconductivity with optically active semiconductors,more » with quantum information being transferred between the two by means of the superconducting proximity effect. Obtaining good interfaces between superconductor and semiconductor is the next obvious step for improving these hybrid systems. As a result, we report on our observation of superconductivity in self-assembled indium structures grown epitaxially on the surface of semiconductor material.« less

Hybrid quantum systems: Outsourcing superconducting qubits

NASA Astrophysics Data System (ADS)

Cleland, Andrew

Superconducting qubits offer excellent prospects for manipulating quantum information, with good qubit lifetimes, high fidelity single- and two-qubit gates, and straightforward scalability (admittedly with multi-dimensional interconnect challenges). One interesting route for experimental development is the exploration of hybrid systems, i.e. coupling superconducting qubits to other systems. I will report on our group's efforts to develop approaches that will allow interfacing superconducting qubits in a quantum-coherent fashion to spin defects in solids, to optomechanical devices, and to resonant nanomechanical structures. The longer term goals of these efforts include transferring quantum states between different qubit systems; generating and receiving ``flying'' acoustic phonon-based as well as optical photon-based qubits; and ultimately developing systems that can be used for quantum memory, quantum computation and quantum communication, the last in both the microwave and fiber telecommunications bands. Work is supported by Grants from AFOSR, ARO, DOE and NSF.

Quantum information processing with superconducting circuits: a review.

PubMed

Wendin, G

2017-10-01

During the last ten years, superconducting circuits have passed from being interesting physical devices to becoming contenders for near-future useful and scalable quantum information processing (QIP). Advanced quantum simulation experiments have been shown with up to nine qubits, while a demonstration of quantum supremacy with fifty qubits is anticipated in just a few years. Quantum supremacy means that the quantum system can no longer be simulated by the most powerful classical supercomputers. Integrated classical-quantum computing systems are already emerging that can be used for software development and experimentation, even via web interfaces. Therefore, the time is ripe for describing some of the recent development of superconducting devices, systems and applications. As such, the discussion of superconducting qubits and circuits is limited to devices that are proven useful for current or near future applications. Consequently, the centre of interest is the practical applications of QIP, such as computation and simulation in Physics and Chemistry.

Quantum information processing with superconducting circuits: a review

NASA Astrophysics Data System (ADS)

Wendin, G.

2017-10-01

During the last ten years, superconducting circuits have passed from being interesting physical devices to becoming contenders for near-future useful and scalable quantum information processing (QIP). Advanced quantum simulation experiments have been shown with up to nine qubits, while a demonstration of quantum supremacy with fifty qubits is anticipated in just a few years. Quantum supremacy means that the quantum system can no longer be simulated by the most powerful classical supercomputers. Integrated classical-quantum computing systems are already emerging that can be used for software development and experimentation, even via web interfaces. Therefore, the time is ripe for describing some of the recent development of superconducting devices, systems and applications. As such, the discussion of superconducting qubits and circuits is limited to devices that are proven useful for current or near future applications. Consequently, the centre of interest is the practical applications of QIP, such as computation and simulation in Physics and Chemistry.

Neutron detection using a current biased kinetic inductance detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shishido, Hiroaki, E-mail: shishido@pe.osakafu-u.ac.jp; Miyajima, Shigeyuki; Ishida, Takekazu

2015-12-07

We demonstrate neutron detection using a solid state superconducting current biased kinetic inductance detector (CB-KID), which consists of a superconducting Nb meander line of 1 μm width and 40 nm thickness. {sup 10}B-enriched neutron absorber layer of 150 nm thickness is placed on top of the CB-KID. Our neutron detectors are able to operate in a wide superconducting region in the bias current–temperature diagram. This is in sharp contrast with our preceding current-biased transition edge detector, which can operate only in a narrow range just below the superconducting critical temperature. The full width at half maximum of the signals remains of the ordermore » of a few tens of ns, which confirms the high speed operation of our detectors.« less

A superconducting nanowire can be modeled by using SPICE

NASA Astrophysics Data System (ADS)

Berggren, Karl K.; Zhao, Qing-Yuan; Abebe, Nathnael; Chen, Minjie; Ravindran, Prasana; McCaughan, Adam; Bardin, Joseph C.

2018-05-01

Modeling of superconducting nanowire single-photon detectors typically requires custom simulations or finite-element analysis in one or two dimensions. Here, we demonstrate two simplified one-dimensional SPICE models of a superconducting nanowire that can quickly and efficiently describe the electrical characteristics of a superconducting nanowire. These models may be of particular use in understanding alternative architectures for nanowire detectors and readouts.

Fabrication of Superconducting Detectors for Studying the Universe

NASA Technical Reports Server (NTRS)

Brown, Ari-David

2012-01-01

Superconducting detectors offer unparalleled means of making astronomical/cosmological observations. Fabrication of these detectors is somewhat unconventional; however, a lot of novel condensed matter physics/materials scientific discoveries and semiconductor fabrication processes can be generated in making these devices.

Waveguide-Coupled Superconducting Nanowire Single-Photon Detectors

NASA Technical Reports Server (NTRS)

Beyer, Andrew D.; Briggs, Ryan M.; Marsili, Francesco; Cohen, Justin D.; Meenehan, Sean M.; Painter, Oskar J.; Shaw, Matthew D.

2015-01-01

We have demonstrated WSi-based superconducting nanowire single-photon detectors coupled to SiNx waveguides with integrated ring resonators. This photonics platform enables the implementation of robust and efficient photon-counting detectors with fine spectral resolution near 1550 nm.

Quantum routing of single optical photons with a superconducting flux qubit

NASA Astrophysics Data System (ADS)

Xia, Keyu; Jelezko, Fedor; Twamley, Jason

2018-05-01

Interconnecting optical photons with superconducting circuits is a challenging problem but essential for building long-range superconducting quantum networks. We propose a hybrid quantum interface between the microwave and optical domains where the propagation of a single-photon pulse along a nanowaveguide is controlled in a coherent way by tuning the electromagnetically induced transparency window with the quantum state of a flux qubit mediated by the spin in a nanodiamond. The qubit can route a single-photon pulse using the nanodiamond into a quantum superposition of paths without the aid of an optical cavity—simplifying the setup. By preparing the flux qubit in a superposition state our cavityless scheme creates a hybrid state-path entanglement between a flying single optical photon and a static superconducting qubit.

Metallic quantum critical points with finite BCS couplings

NASA Astrophysics Data System (ADS)

Raghu, Srinivas

The problem of superconductivity near quantum critical points (QCPs) remains a central topic of modern condensed matter physics. In such systems, there is a competition between the enhanced pairing tendency due to the presence of long-range attractive interactions near criticality, and the suppression of superconductivity due to the destruction of Landau quasiparticles. I will describe some recent work that addresses these competing effects in the context of a solvable model of a metallic quantum critical point. I will show that the two effects - namely the enhanced pairing and the destruction of Landau quasiparticles - can offset one another, resulting in stable ''naked'' quantum critical points without superconductivity. However, the resulting quantum critical metal exhibits strong superconducting fluctuations on all length scales. Reference: S.R., Gonzalo Torroba, and Huajia Wang, arXiv1507.06652, PRB(2015).

Superconducting resonators as beam splitters for linear-optics quantum computation.

PubMed

Chirolli, Luca; Burkard, Guido; Kumar, Shwetank; Divincenzo, David P

2010-06-11

We propose and analyze a technique for producing a beam-splitting quantum gate between two modes of a ring-resonator superconducting cavity. The cavity has two integrated superconducting quantum interference devices (SQUIDs) that are modulated by applying an external magnetic field. The gate is accomplished by applying a radio frequency pulse to one of the SQUIDs at the difference of the two mode frequencies. Departures from perfect beam splitting only arise from corrections to the rotating wave approximation; an exact calculation gives a fidelity of >0.9992. Our construction completes the toolkit for linear-optics quantum computing in circuit quantum electrodynamics.

Detection of geometric phases in superconducting nanocircuits

PubMed

Falci; Fazio; Palma; Siewert; Vedral

2000-09-21

When a quantum-mechanical system undergoes an adiabatic cyclic evolution, it acquires a geometrical phase factor' in addition to the dynamical one; this effect has been demonstrated in a variety of microscopic systems. Advances in nanotechnology should enable the laws of quantum dynamics to be tested at the macroscopic level, by providing controllable artificial two-level systems (for example, in quantum dots and superconducting devices). Here we propose an experimental method to detect geometric phases in a superconducting device. The setup is a Josephson junction nanocircuit consisting of a superconducting electron box. We discuss how interferometry based on geometrical phases may be realized, and show how the effect may be applied to the design of gates for quantum computation.

Implementing quantum optics with parametrically driven superconducting circuits

NASA Astrophysics Data System (ADS)

Aumentado, Jose

Parametric coupling has received much attention, in part because it forms the core of many low-noise amplifiers in superconducting quantum information experiments. However, parametric coupling in superconducting circuits is, as a general rule, simple to generate and forms the basis of a methodology for interacting microwave fields at different frequencies. In the quantum regime, this has important consequences, allowing relative novices to do experiments in superconducting circuits today that were previously heroic efforts in quantum optics and cavity-QED. In this talk, I'll give an overview of some of our work demonstrating parametric coupling within the context of circuit-QED as well as some of the possibilities this concept creates in our field.

NIS tunnel junction as an x-ray photon sensor

NASA Astrophysics Data System (ADS)

Azgui, Fatma; Mears, Carl A.; Labov, Simon E.; Frank, Matthias A.; Sadoulet, Bernard; Brunet, E.; Hiller, Lawrence J.; Lindeman, Mark A.; Netel, Harrie

1995-09-01

This work presents the first results of our development of normal-insulating-superconducting tunnel junctions used as energy dispersive detectors for low energy particles. The device described here is a Ag/Al(subscript 2)O(subscript 3)/Al tunnel junction of area 1.5 multiplied by 10(superscript 4) micrometer squared with thicknesses of 200 nm for the normal Ag strip and 100 nm for the superconducting Al film. Two different high-speed SQUID systems manufactured by quantum magnetics and HYPRES, respectively, were used for the readout of this device. At 80 mK bath temperature we obtained an energy resolution DeltaE(subscript FWHM) equals 250 eV for 5.89 keV x rays absorbed directly in the normal metal. This energy resolution appears to be limited in large part by the observed strong position dependence of the device response.

Two-dimensional lattice gauge theories with superconducting quantum circuits

PubMed Central

Marcos, D.; Widmer, P.; Rico, E.; Hafezi, M.; Rabl, P.; Wiese, U.-J.; Zoller, P.

2014-01-01

A quantum simulator of U(1) lattice gauge theories can be implemented with superconducting circuits. This allows the investigation of confined and deconfined phases in quantum link models, and of valence bond solid and spin liquid phases in quantum dimer models. Fractionalized confining strings and the real-time dynamics of quantum phase transitions are accessible as well. Here we show how state-of-the-art superconducting technology allows us to simulate these phenomena in relatively small circuit lattices. By exploiting the strong non-linear couplings between quantized excitations emerging when superconducting qubits are coupled, we show how to engineer gauge invariant Hamiltonians, including ring-exchange and four-body Ising interactions. We demonstrate that, despite decoherence and disorder effects, minimal circuit instances allow us to investigate properties such as the dynamics of electric flux strings, signaling confinement in gauge invariant field theories. The experimental realization of these models in larger superconducting circuits could address open questions beyond current computational capability. PMID:25512676

Gapless Andreev bound states in the quantum spin Hall insulator HgTe.

PubMed

Bocquillon, Erwann; Deacon, Russell S; Wiedenmann, Jonas; Leubner, Philipp; Klapwijk, Teunis M; Brüne, Christoph; Ishibashi, Koji; Buhmann, Hartmut; Molenkamp, Laurens W

2017-02-01

In recent years, Majorana physics has attracted considerable attention because of exotic new phenomena and its prospects for fault-tolerant topological quantum computation. To this end, one needs to engineer the interplay between superconductivity and electronic properties in a topological insulator, but experimental work remains scarce and ambiguous. Here, we report experimental evidence for topological superconductivity induced in a HgTe quantum well, a 2D topological insulator that exhibits the quantum spin Hall (QSH) effect. The a.c. Josephson effect demonstrates that the supercurrent has a 4π periodicity in the superconducting phase difference, as indicated by a doubling of the voltage step for multiple Shapiro steps. In addition, this response like that of a superconducting quantum interference device to a perpendicular magnetic field shows that the 4π-periodic supercurrent originates from states located on the edges of the junction. Both features appear strongest towards the QSH regime, and thus provide evidence for induced topological superconductivity in the QSH edge states.

Quantum acoustics with superconducting qubits

NASA Astrophysics Data System (ADS)

Chu, Yiwen; Kharel, Prashanta; Renninger, William H.; Burkhart, Luke D.; Frunzio, Luigi; Rakich, Peter T.; Schoelkopf, Robert J.

2017-10-01

Mechanical objects have important practical applications in the fields of quantum information and metrology as quantum memories or transducers for measuring and connecting different types of quantum systems. The field of electromechanics is in pursuit of a robust and highly coherent device that couples motion to nonlinear quantum objects such as superconducting qubits. Here, we experimentally demonstrate a high-frequency bulk acoustic wave resonator that is strongly coupled to a superconducting qubit using piezoelectric transduction with a cooperativity of 260. We measure qubit and mechanical coherence times on the order of 10 microseconds. Our device requires only simple fabrication methods and provides controllable access to a multitude of phonon modes. We demonstrate quantum control and measurement on gigahertz phonons at the single-quantum level.

Macroscopic Quantum Tunneling in Superconducting Junctions of β-Ag2Se Topological Insulator Nanowire.

PubMed

Kim, Jihwan; Kim, Bum-Kyu; Kim, Hong-Seok; Hwang, Ahreum; Kim, Bongsoo; Doh, Yong-Joo

2017-11-08

We report on the fabrication and electrical transport properties of superconducting junctions made of β-Ag 2 Se topological insulator (TI) nanowires in contact with Al superconducting electrodes. The temperature dependence of the critical current indicates that the superconducting junction belongs to a short and diffusive junction regime. As a characteristic feature of the narrow junction, the critical current decreases monotonously with increasing magnetic field. The stochastic distribution of the switching current exhibits the macroscopic quantum tunneling behavior, which is robust up to T = 0.8 K. Our observations indicate that the TI nanowire-based Josephson junctions can be a promising building block for the development of nanohybrid superconducting quantum bits.

MOCCA: A 4k-Pixel Molecule Camera for the Position- and Energy-Resolving Detection of Neutral Molecule Fragments at CSR

NASA Astrophysics Data System (ADS)

Gamer, L.; Schulz, D.; Enss, C.; Fleischmann, A.; Gastaldo, L.; Kempf, S.; Krantz, C.; Novotný, O.; Schwalm, D.; Wolf, A.

2016-08-01

We present the design of MOCCA, a large-area particle detector that is developed for the position- and energy-resolving detection of neutral molecule fragments produced in electron-ion interactions at the Cryogenic Storage Ring at the Max Planck Institute for Nuclear Physics in Heidelberg. The detector is based on metallic magnetic calorimeters and consists of 4096 particle absorbers covering a total detection area of 44.8 mathrm {mm} × 44.8 mathrm {mm}. Groups of four absorbers are thermally coupled to a common paramagnetic temperature sensor where the strength of the thermal link is different for each absorber. This allows attributing a detector event within this group to the corresponding absorber by discriminating the signal rise times. A novel readout scheme further allows reading out all 1024 temperature sensors that are arranged in a 32 × 32 square array using only 16+16 current-sensing superconducting quantum interference devices. Numerical calculations taking into account a simplified detector model predict an energy resolution of Δ E_mathrm {FWHM} le 80 mathrm {eV} for all pixels of this detector.

The Quantum Socket: Wiring for Superconducting Qubits - Part 2

NASA Astrophysics Data System (ADS)

Bejanin, J. H.; McConkey, T. G.; Rinehart, J. R.; Bateman, J. D.; Earnest, C. T.; McRae, C. H.; Rohanizadegan, Y.; Shiri, D.; Mariantoni, M.; Penava, B.; Breul, P.; Royak, S.; Zapatka, M.; Fowler, A. G.

Quantum computing research has reached a level of maturity where quantum error correction (QEC) codes can be executed on linear arrays of superconducting quantum bits (qubits). A truly scalable quantum computing architecture, however, based on practical QEC algorithms, requires nearest neighbor interaction between qubits on a two-dimensional array. Such an arrangement is not possible with techniques that rely on wire bonding. To address this issue, we have developed the quantum socket, a device based on three-dimensional wires that enables the control of superconducting qubits on a two-dimensional grid. In this talk, we present experimental results characterizing this type of wiring. We will show that the quantum socket performs exceptionally well for the transmission and reflection of microwave signals up to 10 GHz, while minimizing crosstalk between adjacent wires. Under realistic conditions, we measured an S21 of -5 dB at 6 GHz and an average crosstalk of -60 dB. We also describe time domain reflectometry results and arbitrary pulse transmission tests, showing that the quantum socket can be used to control superconducting qubits.

Optical Probe of the Superconducting Normal Mixed State in a Magnetic Penetration Thermometer

NASA Technical Reports Server (NTRS)

Stevenson, T. R.; Balvin, M. A.; Bandler, S. R.; Denis, K. L.; Lee, S. -J.; Nagler, P. C.; Smith, S. J.

2016-01-01

Using ultraviolet photon pulses, we have probed the internal behavior of a molybdenum-gold Magnetic Penetration Thermometer (MPT) that we designed for x-ray microcalorimetry. In this low-temperature detector, the diamagnetic response of a superconducting MoAu bilayer is used to sense temperature changes in response to absorbed photons. We have previously described an approximate model that explains the high responsivity of the detector to temperature changes as a consequence of a Meissner transition of the molybdenum-gold film in the magnetic field applied by the superconducting circuit used to bias the detector. We compare measurements of MPT heat capacity and thermal conductance, derived from UV photon pulse data, to our model predictions for the thermodynamic properties of the sensor and for the electron cooling obtained by quasiparticle recombination. Our data on electron cooling power is also relevant to the operation of other superconducting detectors, such as Microwave Kinetic Inductance Detectors.

Non-Fermi-liquid superconductivity: Eliashberg approach versus the renormalization group

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Huajia; Raghu, Srinivas; Torroba, Gonzalo

Here, we address the problem of superconductivity for non-Fermi liquids using two commonly adopted, yet apparently distinct, methods: (1) the renormalization group (RG) and (2) Eliashberg theory. The extent to which both methods yield consistent solutions for the low-energy behavior of quantum metals has remained unclear. We show that the perturbative RG beta function for the 4-Fermi coupling can be explicitly derived from the linearized Eliashberg equations, under the assumption that quantum corrections are approximately local across energy scales. We apply our analysis to the test case of phonon-mediated superconductivity and show the consistency of both the Eliashberg and RGmore » treatments. We next study superconductivity near a class of quantum critical points and find a transition between superconductivity and a “naked” metallic quantum critical point with finite, critical BCS couplings. We speculate on the applications of our theory to the phenomenology of unconventional metals.« less

Non-Fermi-liquid superconductivity: Eliashberg approach versus the renormalization group

DOE PAGES

Wang, Huajia; Raghu, Srinivas; Torroba, Gonzalo

2017-04-15

Here, we address the problem of superconductivity for non-Fermi liquids using two commonly adopted, yet apparently distinct, methods: (1) the renormalization group (RG) and (2) Eliashberg theory. The extent to which both methods yield consistent solutions for the low-energy behavior of quantum metals has remained unclear. We show that the perturbative RG beta function for the 4-Fermi coupling can be explicitly derived from the linearized Eliashberg equations, under the assumption that quantum corrections are approximately local across energy scales. We apply our analysis to the test case of phonon-mediated superconductivity and show the consistency of both the Eliashberg and RGmore » treatments. We next study superconductivity near a class of quantum critical points and find a transition between superconductivity and a “naked” metallic quantum critical point with finite, critical BCS couplings. We speculate on the applications of our theory to the phenomenology of unconventional metals.« less

Quantum State Transmission in a Superconducting Charge Qubit-Atom Hybrid

PubMed Central

Yu, Deshui; Valado, María Martínez; Hufnagel, Christoph; Kwek, Leong Chuan; Amico, Luigi; Dumke, Rainer

2016-01-01

Hybrids consisting of macroscopic superconducting circuits and microscopic components, such as atoms and spins, have the potential of transmitting an arbitrary state between different quantum species, leading to the prospective of high-speed operation and long-time storage of quantum information. Here we propose a novel hybrid structure, where a neutral-atom qubit directly interfaces with a superconducting charge qubit, to implement the qubit-state transmission. The highly-excited Rydberg atom located inside the gate capacitor strongly affects the behavior of Cooper pairs in the box while the atom in the ground state hardly interferes with the superconducting device. In addition, the DC Stark shift of the atomic states significantly depends on the charge-qubit states. By means of the standard spectroscopic techniques and sweeping the gate voltage bias, we show how to transfer an arbitrary quantum state from the superconducting device to the atom and vice versa. PMID:27922087

Implementation of adiabatic geometric gates with superconducting phase qubits.

PubMed

Peng, Z H; Chu, H F; Wang, Z D; Zheng, D N

2009-01-28

We present an adiabatic geometric quantum computation strategy based on the non-degenerate energy eigenstates in (but not limited to) superconducting phase qubit systems. The fidelity of the designed quantum gate was evaluated in the presence of simulated thermal fluctuations in a superconducting phase qubits circuit and was found to be quite robust against random errors. In addition, it was elucidated that the Berry phase in the designed adiabatic evolution may be detected directly via the quantum state tomography developed for superconducting qubits. We also analyze the effects of control parameter fluctuations on the experimental detection of the Berry phase.

Coherent quantum dynamics of a superconducting flux qubit.

PubMed

Chiorescu, I; Nakamura, Y; Harmans, C J P M; Mooij, J E

2003-03-21

We have observed coherent time evolution between two quantum states of a superconducting flux qubit comprising three Josephson junctions in a loop. The superposition of the two states carrying opposite macroscopic persistent currents is manipulated by resonant microwave pulses. Readout by means of switching-event measurement with an attached superconducting quantum interference device revealed quantum-state oscillations with high fidelity. Under strong microwave driving, it was possible to induce hundreds of coherent oscillations. Pulsed operations on this first sample yielded a relaxation time of 900 nanoseconds and a free-induction dephasing time of 20 nanoseconds. These results are promising for future solid-state quantum computing.

Error budgeting single and two qubit gates in a superconducting qubit

NASA Astrophysics Data System (ADS)

Chen, Z.; Chiaro, B.; Dunsworth, A.; Foxen, B.; Neill, C.; Quintana, C.; Wenner, J.; Martinis, John. M.; Google Quantum Hardware Team Team

Superconducting qubits have shown promise as a platform for both error corrected quantum information processing and demonstrations of quantum supremacy. High fidelity quantum gates are crucial to achieving both of these goals, and superconducting qubits have demonstrated two qubit gates exceeding 99% fidelity. In order to improve gate fidelity further, we must understand the remaining sources of error. In this talk, I will demonstrate techniques for quantifying the contributions of control, decoherence, and leakage to gate error, for both single and two qubit gates. I will also discuss the near term outlook for achieving quantum supremacy using a gate-based approach in superconducting qubits. This work is supported Google Inc., and by the National Science Foundation Graduate Research Fellowship under Grant No. DGE 1605114.

A multilayered approach to superconducting tunnel junction x ray detectors

NASA Technical Reports Server (NTRS)

Rippert, E. D.; Song, S. N.; Ketterson, J. B.; Maglic, S. R.; Lomatch, S.; Thomas, C.; Cheida, M. A.; Ulmer, M. P.

1992-01-01

'First generation' superconducting tunnel junction X-ray detectors (characterized by a single tunnel junction in direct contact with its substrate, with totally external amplification) remain more than an order of magnitude away from their theoretical energy resolutions which are in the order of eV's. The difficulties that first generation devices are encountering are being attacked by a 'second generation' of superconducting X-ray detector designs including quasiparticle trapping configurations and Josephson junction arrays. A second generation design concept, the multilayered superconducting tunnel junction X-ray detector, consisting of tens to hundreds of tunnel junctions stacked on top of one another (a superlattice), is presented. Some of the possibilities of this engineered materials approach include the tuning of phonon transmission characteristics of the material, suppression of parasitic quasiparticle trapping and intrinsic amplification.

Impurity-generated non-Abelions

NASA Astrophysics Data System (ADS)

Simion, G.; Kazakov, A.; Rokhinson, L. P.; Wojtowicz, T.; Lyanda-Geller, Y. B.

2018-06-01

Two classes of topological superconductors and Majorana modes in condensed matter systems are known to date: one in which disorder induced by impurities strongly suppresses topological superconducting gap and is detrimental to Majorana modes, and another where Majorana fermions are protected by a disorder-robust topological superconductor gap. Observation and control of Majorana fermions and other non-Abelions often requires a symmetry of an underlying system leading to a gap in the single-particle or quasiparticle spectra. In semiconductor structures, impurities that provide charge carriers introduce states into the gap and enable conductance and proximity-induced superconductivity via the in-gap states. Thus a third class of topological superconductivity and Majorana modes emerges, in which topological superconductivity and Majorana fermions appear exclusively when impurities generate in-gap states. We show that impurity-enabled topological superconductivity is realized in a quantum Hall ferromagnet, when a helical domain wall is coupled to an s -wave superconductor. As an example of emergence of topological superconductivity in quantum Hall ferromagnets, we consider the integer quantum Hall effect in Mn-doped CdTe quantum wells. Recent experiments on transport through the quantum Hall ferromagnet domain wall in this system indicated a vital role of impurities in the conductance, but left unresolved the question whether impurities preclude generation of Majorana fermions and other non-Abelions in such systems in general. Here, solving a general quantum-mechanical problem of impurity bound states in a system of spin-orbit coupled Landau levels, we demonstrate that impurity-induced Majorana modes emerge at boundaries between topological and conventional superconducting states generated in a domain wall due to proximity to an s superconductor. We consider both short-range disorder and a smooth random potential. The phase diagram of the system is defined by characteristic disorder, gate voltage induced angular momentum splitting of impurity levels, and by a proximity superconducting gap. The phase diagram exhibits two ranges of gate voltage with conventional superconducting order separated by a gate voltage range with topological superconductivity. We show that electrostatic control of domain walls in an integer quantum Hall ferromagnet allows manipulation of Majorana fermions. Ferromagnetic transitions in the fractional quantum Hall regime may lead to the formation and electrostatic control of higher order non-Abelian excitations.

Decoy-state quantum key distribution with polarized photons over 200 km.

PubMed

Liu, Yang; Chen, Teng-Yun; Wang, Jian; Cai, Wen-Qi; Wan, Xu; Chen, Luo-Kan; Wang, Jin-Hong; Liu, Shu-Bin; Liang, Hao; Yang, Lin; Peng, Cheng-Zhi; Chen, Kai; Chen, Zeng-Bing; Pan, Jian-Wei

2010-04-12

We report an implementation of decoy-state quantum key distribution (QKD) over 200 km optical fiber cable through photon polarization encoding. This is achieved by constructing the whole QKD system operating at 320 MHz repetition rate, and developing high-speed transmitter and receiver modules. A novel and economic way of synchronization method is designed and incorporated into the system, which allows to work at a low frequency of 40kHz and removes the use of highly precise clock. A final key rate of 15 Hz is distributed within the experimental time of 3089 seconds, by using super-conducting single photon detectors. This is longest decoy-state QKD yet demonstrated up to date. It helps to make a significant step towards practical secure communication in long-distance scope.

Projected Dipole Moments of Individual Two-Level Defects Extracted Using Circuit Quantum Electrodynamics.

PubMed

Sarabi, B; Ramanayaka, A N; Burin, A L; Wellstood, F C; Osborn, K D

2016-04-22

Material-based two-level systems (TLSs), appearing as defects in low-temperature devices including superconducting qubits and photon detectors, are difficult to characterize. In this study we apply a uniform dc electric field across a film to tune the energies of TLSs within. The film is embedded in a superconducting resonator such that it forms a circuit quantum electrodynamical system. The energy of individual TLSs is observed as a function of the known tuning field. By studying TLSs for which we can determine the tunneling energy, the actual p_{z}, dipole moments projected along the uniform field direction, are individually obtained. A distribution is created with 60 p_{z}. We describe the distribution using a model with two dipole moment magnitudes, and a fit yields the corresponding values p=p_{1}=2.8±0.2  D and p=p_{2}=8.3±0.4  D. For a strong-coupled TLS the vacuum-Rabi splitting can be obtained with p_{z} and tunneling energy. This allows a measurement of the circuit's zero-point electric-field fluctuations, in a method that does not need the electric-field volume.

Josephson Photodetectors via Temperature-to-Phase Conversion

NASA Astrophysics Data System (ADS)

Virtanen, P.; Ronzani, A.; Giazotto, F.

2018-05-01

We theoretically investigate the temperature-to-phase conversion (TPC) process occurring in dc superconducting quantum interferometers based on superconductor-normal-metal-superconductor (S -N -S ) mesoscopic Josephson junctions. In particular, we predict the temperature-driven rearrangement of the phase gradients in the interferometer under the fixed constraints of fluxoid quantization and supercurrent conservation. This mechanism allows sizeable phase variations across the junctions for suitable structure parameters and temperatures. We show that the TPC can be a basis for sensitive single-photon sensors or bolometers. We propose a radiation detector realizable with conventional materials and state-of-the-art nanofabrication techniques. Integrated with a superconducting quantum-interference proximity transistor as a readout setup, an aluminum-based TPC calorimeter can provide a large signal-to-noise ratio >100 in the 10-GHz-10-THz frequency range and a resolving power larger than 1 02 below 50 mK for terahertz photons. In the bolometric operation, electrical noise equivalent power of approximately 10-22 W /√{Hz } is predicted at 50 mK. This device can be attractive as a cryogenic single-photon sensor operating in the giga- and terahertz regime with applications in dark-matter searches.

Exploring quantum thermodynamics in continuous measurement of superconducting qubits

NASA Astrophysics Data System (ADS)

Murch, Kater

The extension of thermodynamics into the realm of quantum mechanics, where quantum fluctuations dominate and systems need not occupy definite states, poses unique challenges. Superconducting quantum circuits offer exquisite control over the environment of simple quantum systems allowing the exploration of thermodynamics at the quantum level through measurement and feedback control. We use a superconducting transmon qubit that is resonantly coupled to a waveguide cavity as an effectively one-dimensional quantum emitter. By driving the emitter and detecting the fluorescence with a near-quantum-limited Josephson parametric amplifier, we track the evolution of the quantum state and characterize the work and heat along single quantum trajectories. By using quantum feedback control to compensate for heat exchanged with the emitter's environment we are able to extract the work statistics associated with the quantum evolution and examine fundamental fluctuation theorems in non-equilibrium thermodynamics. This work was supported by the Alfred P. Sloan Foundation, the National Science Foundation, and the Office of Naval Research.

Quantum state transfer and controlled-phase gate on one-dimensional superconducting resonators assisted by a quantum bus.

PubMed

Hua, Ming; Tao, Ming-Jie; Deng, Fu-Guo

2016-02-24

We propose a quantum processor for the scalable quantum computation on microwave photons in distant one-dimensional superconducting resonators. It is composed of a common resonator R acting as a quantum bus and some distant resonators rj coupled to the bus in different positions assisted by superconducting quantum interferometer devices (SQUID), different from previous processors. R is coupled to one transmon qutrit, and the coupling strengths between rj and R can be fully tuned by the external flux through the SQUID. To show the processor can be used to achieve universal quantum computation effectively, we present a scheme to complete the high-fidelity quantum state transfer between two distant microwave-photon resonators and another one for the high-fidelity controlled-phase gate on them. By using the technique for catching and releasing the microwave photons from resonators, our processor may play an important role in quantum communication as well.

Emergence of Quantum Phase-Slip Behaviour in Superconducting NbN Nanowires: DC Electrical Transport and Fabrication Technologies.

PubMed

Constantino, Nicolas G N; Anwar, Muhammad Shahbaz; Kennedy, Oscar W; Dang, Manyu; Warburton, Paul A; Fenton, Jonathan C

2018-06-16

Superconducting nanowires undergoing quantum phase-slips have potential for impact in electronic devices, with a high-accuracy quantum current standard among a possible toolbox of novel components. A key element of developing such technologies is to understand the requirements for, and control the production of, superconducting nanowires that undergo coherent quantum phase-slips. We present three fabrication technologies, based on using electron-beam lithography or neon focussed ion-beam lithography, for defining narrow superconducting nanowires, and have used these to create nanowires in niobium nitride with widths in the range of 20⁻250 nm. We present characterisation of the nanowires using DC electrical transport at temperatures down to 300 mK. We demonstrate that a range of different behaviours may be obtained in different nanowires, including bulk-like superconducting properties with critical-current features, the observation of phase-slip centres and the observation of zero conductance below a critical voltage, characteristic of coherent quantum phase-slips. We observe critical voltages up to 5 mV, an order of magnitude larger than other reports to date. The different prominence of quantum phase-slip effects in the various nanowires may be understood as arising from the differing importance of quantum fluctuations. Control of the nanowire properties will pave the way for routine fabrication of coherent quantum phase-slip nanowire devices for technology applications.

The Quantum Socket: Wiring for Superconducting Qubits - Part 3

NASA Astrophysics Data System (ADS)

Mariantoni, M.; Bejianin, J. H.; McConkey, T. G.; Rinehart, J. R.; Bateman, J. D.; Earnest, C. T.; McRae, C. H.; Rohanizadegan, Y.; Shiri, D.; Penava, B.; Breul, P.; Royak, S.; Zapatka, M.; Fowler, A. G.

The implementation of a quantum computer requires quantum error correction codes, which allow to correct errors occurring on physical quantum bits (qubits). Ensemble of physical qubits will be grouped to form a logical qubit with a lower error rate. Reaching low error rates will necessitate a large number of physical qubits. Thus, a scalable qubit architecture must be developed. Superconducting qubits have been used to realize error correction. However, a truly scalable qubit architecture has yet to be demonstrated. A critical step towards scalability is the realization of a wiring method that allows to address qubits densely and accurately. A quantum socket that serves this purpose has been designed and tested at microwave frequencies. In this talk, we show results where the socket is used at millikelvin temperatures to measure an on-chip superconducting resonator. The control electronics is another fundamental element for scalability. We will present a proposal based on the quantum socket to interconnect a classical control hardware to a superconducting qubit hardware, where both are operated at millikelvin temperatures.

Coupling Monte Carlo simulations with thermal analysis for correcting microdosimetric spectra from a novel micro-calorimeter

NASA Astrophysics Data System (ADS)

Fathi, K.; Galer, S.; Kirkby, K. J.; Palmans, H.; Nisbet, A.

2017-11-01

The high uncertainty in the Relative Biological Effectiveness (RBE) values of particle therapy beam, which are used in combination with the quantity absorbed dose in radiotherapy, together with the increase in the number of particle therapy centres worldwide necessitate a better understating of the biological effect of such modalities. The present novel study is part of performance testing and development of a micro-calorimeter based on Superconducting QUantum Interference Devices (SQUIDs). Unlike other microdosimetric detectors that are used for investigating the energy distribution, this detector provides a direct measurement of energy deposition at the micrometre scale, that can be used to improve our understanding of biological effects in particle therapy application, radiation protection and environmental dosimetry. Temperature rises of less than 1μK are detectable and when combined with the low specific heat capacity of the absorber at cryogenic temperature, extremely high energy deposition sensitivity of approximately 0.4 eV can be achieved. The detector consists of 3 layers: tissue equivalent (TE) absorber, superconducting (SC) absorber and silicon substrate. Ideally all energy would be absorbed in the TE absorber and heat rise in the superconducting layer would arise due to heat conduction from the TE layer. However, in practice direct particle absorption occurs in all 3 layers and must be corrected for. To investigate the thermal behaviour within the detector, and quantify any possible correction, particle tracks were simulated employing Geant4 (v9.6) Monte Carlo simulations. The track information was then passed to the COMSOL Multiphysics (Finite Element Method) software. The 3D heat transfer within each layer was then evaluated in a time-dependent model. For a statistically reliable outcome, the simulations had to be repeated for a large number of particles. An automated system has been developed that couples Geant4 Monte Carlo output to COMSOL for determining the expected distribution of proton tracks and their thermal contribution within the detector. The correction factor for a 3.8 MeV proton pencil beam was determined and applied to the expected spectra. The corrected microdosimetric spectra was shown to have a good agreement with the ideal spectra.

Superconductivity mediated by quantum critical antiferromagnetic fluctuations: The rise and fall of hot spots

NASA Astrophysics Data System (ADS)

Wang, Xiaoyu; Schattner, Yoni; Berg, Erez; Fernandes, Rafael M.

2017-05-01

In several unconventional superconductors, the highest superconducting transition temperature Tc is found in a region of the phase diagram where the antiferromagnetic transition temperature extrapolates to zero, signaling a putative quantum critical point. The elucidation of the interplay between these two phenomena—high-Tc superconductivity and magnetic quantum criticality—remains an important piece of the complex puzzle of unconventional superconductivity. In this paper, we combine sign-problem-free quantum Monte Carlo simulations and field-theoretical analytical calculations to unveil the microscopic mechanism responsible for the superconducting instability of a general low-energy model, called the spin-fermion model. In this approach, low-energy electronic states interact with each other via the exchange of quantum critical magnetic fluctuations. We find that even in the regime of moderately strong interactions, both the superconducting transition temperature and the pairing susceptibility are governed not by the properties of the entire Fermi surface, but instead by the properties of small portions of the Fermi surface called hot spots. Moreover, Tc increases with increasing interaction strength, until it starts to saturate at the crossover from hot-spots-dominated to Fermi-surface-dominated pairing. Our work provides not only invaluable insights into the system parameters that most strongly affect Tc, but also important benchmarks to assess the origin of superconductivity in both microscopic models and actual materials.

5,120 Superconducting Bolometers for the PIPER Balloon-Borne CMB Polarization Experiment

NASA Technical Reports Server (NTRS)

Benford, Dominic J.; Chuss, David T.; Hilton, Gene C.; Irwin, Kent D.; Jethava, Nikhil; Jhabvala, Christine A.; Kogut, Alan J.; Miller, Timothy M.; Moseley, S. Harvey; Rostem, Karwan;

5,120 Superconducting Bolometers for the PIPER Balloon-Borne CMB Polarization Experiment

NASA Technical Reports Server (NTRS)

Benford, Dominic J.; Chuss, David T.; Hilton, Gene C.; Irwin, Kent D.; Jethava, Nikhil S.; Jhabvala, Christine A.; Kogut, Alan J.; Miller, Timothy M.; Mirel, Paul; Moseley, S. Harvey;

Superconducting Magnetometry for Cardiovascular Studies and AN Application of Adaptive Filtering.

NASA Astrophysics Data System (ADS)

Leifer, Mark Curtis

Sensitive magnetic detectors utilizing Superconducting Quantum Interference Devices (SQUID's) have been developed and used for studying the cardiovascular system. The theory of magnetic detection of cardiac currents is discussed, and new experimental data supporting the validity of the theory is presented. Measurements on both humans and dogs, in both healthy and diseased states, are presented using the new technique, which is termed vector magnetocardiography. In the next section, a new type of superconducting magnetometer with a room temperature pickup is analyzed, and techniques for optimizing its sensitivity to low-frequency sub-microamp currents are presented. Performance of the actual device displays significantly improved sensitivity in this frequency range, and the ability to measure currents in intact, in vivo biological fibers. The final section reviews the theoretical operation of a digital self-optimizing filter, and presents a four-channel software implementation of the system. The application of the adaptive filter to enhancement of geomagnetic signals for earthquake forecasting is discussed, and the adaptive filter is shown to outperform existing techniques in suppressing noise from geomagnetic records.

Multiple quantum phase transitions and superconductivity in Ce-based heavy fermions.

PubMed

Weng, Z F; Smidman, M; Jiao, L; Lu, Xin; Yuan, H Q

2016-09-01

Heavy fermions have served as prototype examples of strongly-correlated electron systems. The occurrence of unconventional superconductivity in close proximity to the electronic instabilities associated with various degrees of freedom points to an intricate relationship between superconductivity and other electronic states, which is unique but also shares some common features with high temperature superconductivity. The magnetic order in heavy fermion compounds can be continuously suppressed by tuning external parameters to a quantum critical point, and the role of quantum criticality in determining the properties of heavy fermion systems is an important unresolved issue. Here we review the recent progress of studies on Ce based heavy fermion superconductors, with an emphasis on the superconductivity emerging on the edge of magnetic and charge instabilities as well as the quantum phase transitions which occur by tuning different parameters, such as pressure, magnetic field and doping. We discuss systems where multiple quantum critical points occur and whether they can be classified in a unified manner, in particular in terms of the evolution of the Fermi surface topology.

Unconventional superconductivity and quantum criticality in the heavy fermions CeIrSi3 and CeRhSi3

NASA Astrophysics Data System (ADS)

Landaeta, J. F.; Subero, D.; Catalá, D.; Taylor, S. V.; Kimura, N.; Settai, R.; Īnuki, Y.; Sigrist, M.; Bonalde, I.

2018-03-01

In most strongly correlated electron systems superconductivity appears nearby a magnetic quantum critical point (QCP) which is believed to cause unconventional behaviors. In order to explore this physics, we present here a study of the heavy-fermion superconductors CeIrSi3 and CeRhSi3 carried out using a newly developed system for high-resolution magnetic penetration-depth measurements under pressure. Superconductivity in CeIrSi3 shows a change from an excitation spectrum with a line-nodal gap to one which is entirely gapful when pressure is close but not yet at the QCP. In contrast, CeRhSi3 does not possess a T =0 quantum phase transition and the superconducting phase remains for all accessible pressures with a nodal gap. Combining both results suggests that in these compounds unconventional superconducting behaviors are rather connected with the coexisting antiferromagnetic order. This study provides another viewpoint on the interplay of superconductivity, magnetism, and quantum criticality in CeIrSi3 and CeRhSi3 and maybe in other heavy fermions.

Implementing an ancilla-free 1→M economical phase-covariant quantum cloning machine with superconducting quantum-interference devices in cavity QED

NASA Astrophysics Data System (ADS)

Yu, Long-Bao; Zhang, Wen-Hai; Ye, Liu

2007-09-01

We propose a simple scheme to realize 1→M economical phase-covariant quantum cloning machine (EPQCM) with superconducting quantum interference device (SQUID) qubits. In our scheme, multi-SQUIDs are fixed into a microwave cavity by adiabatic passage for their manipulation. Based on this model, we can realize the EPQCM with high fidelity via adiabatic quantum computation.

Circuit quantum electrodynamics with a spin qubit.

PubMed

Petersson, K D; McFaul, L W; Schroer, M D; Jung, M; Taylor, J M; Houck, A A; Petta, J R

2012-10-18

Electron spins trapped in quantum dots have been proposed as basic building blocks of a future quantum processor. Although fast, 180-picosecond, two-quantum-bit (two-qubit) operations can be realized using nearest-neighbour exchange coupling, a scalable, spin-based quantum computing architecture will almost certainly require long-range qubit interactions. Circuit quantum electrodynamics (cQED) allows spatially separated superconducting qubits to interact via a superconducting microwave cavity that acts as a 'quantum bus', making possible two-qubit entanglement and the implementation of simple quantum algorithms. Here we combine the cQED architecture with spin qubits by coupling an indium arsenide nanowire double quantum dot to a superconducting cavity. The architecture allows us to achieve a charge-cavity coupling rate of about 30 megahertz, consistent with coupling rates obtained in gallium arsenide quantum dots. Furthermore, the strong spin-orbit interaction of indium arsenide allows us to drive spin rotations electrically with a local gate electrode, and the charge-cavity interaction provides a measurement of the resulting spin dynamics. Our results demonstrate how the cQED architecture can be used as a sensitive probe of single-spin physics and that a spin-cavity coupling rate of about one megahertz is feasible, presenting the possibility of long-range spin coupling via superconducting microwave cavities.

Quantum phase slip phenomenon in ultra-narrow superconducting nanorings

NASA Astrophysics Data System (ADS)

Arutyunov, Konstantin Yu.; Hongisto, Terhi T.; Lehtinen, Janne S.; Leino, Leena I.; Vasiliev, Alexander L.

2012-02-01

The smaller the system, typically - the higher is the impact of fluctuations. In narrow superconducting wires sufficiently close to the critical temperature Tc thermal fluctuations are responsible for the experimentally observable finite resistance. Quite recently it became possible to fabricate sub-10 nm superconducting structures, where the finite resistivity was reported within the whole range of experimentally obtainable temperatures. The observation has been associated with quantum fluctuations capable to quench zero resistivity in superconducting nanowires even at temperatures T-->0. Here we demonstrate that in tiny superconducting nanorings the same phenomenon is responsible for suppression of another basic attribute of superconductivity - persistent currents - dramatically affecting their magnitude, the period and the shape of the current-phase relation. The effect is of fundamental importance demonstrating the impact of quantum fluctuations on the ground state of a macroscopically coherent system, and should be taken into consideration in various nanoelectronic applications.

Coherent coupling of a superconducting flux qubit to an electron spin ensemble in diamond.

PubMed

Zhu, Xiaobo; Saito, Shiro; Kemp, Alexander; Kakuyanagi, Kosuke; Karimoto, Shin-ichi; Nakano, Hayato; Munro, William J; Tokura, Yasuhiro; Everitt, Mark S; Nemoto, Kae; Kasu, Makoto; Mizuochi, Norikazu; Semba, Kouichi

2011-10-12

During the past decade, research into superconducting quantum bits (qubits) based on Josephson junctions has made rapid progress. Many foundational experiments have been performed, and superconducting qubits are now considered one of the most promising systems for quantum information processing. However, the experimentally reported coherence times are likely to be insufficient for future large-scale quantum computation. A natural solution to this problem is a dedicated engineered quantum memory based on atomic and molecular systems. The question of whether coherent quantum coupling is possible between such natural systems and a single macroscopic artificial atom has attracted considerable attention since the first demonstration of macroscopic quantum coherence in Josephson junction circuits. Here we report evidence of coherent strong coupling between a single macroscopic superconducting artificial atom (a flux qubit) and an ensemble of electron spins in the form of nitrogen-vacancy colour centres in diamond. Furthermore, we have observed coherent exchange of a single quantum of energy between a flux qubit and a macroscopic ensemble consisting of about 3 × 10(7) such colour centres. This provides a foundation for future quantum memories and hybrid devices coupling microwave and optical systems.

Conductance signatures of odd-frequency superconductivity in quantum spin Hall systems using a quantum point contact

NASA Astrophysics Data System (ADS)

Fleckenstein, C.; Ziani, N. Traverso; Trauzettel, B.

2018-04-01

Topological superconductors give rise to unconventional superconductivity, which is mainly characterized by the symmetry of the superconducting pairing amplitude. However, since the symmetry of the superconducting pairing amplitude is not directly observable, its experimental identification is rather difficult. In our work, we propose a system, composed of a quantum point contact and proximity-induced s -wave superconductivity at the helical edge of a two-dimensional topological insulator, for which we demonstrate the presence of odd-frequency pairing and its intimate connection to unambiguous transport signatures. Notably, our proposal requires no time-reversal symmetry breaking terms. We discover the domination of crossed Andreev reflection over electron cotunneling in a wide range of parameter space, which is a quite unusual transport regime.

Transferring arbitrary d-dimensional quantum states of a superconducting transmon qudit in circuit QED.

PubMed

Liu, Tong; Su, Qi-Ping; Yang, Jin-Hu; Zhang, Yu; Xiong, Shao-Jie; Liu, Jin-Ming; Yang, Chui-Ping

2017-08-01

A qudit (d-level quantum system) has a large Hilbert space and thus can be used to achieve many quantum information and communication tasks. Here, we propose a method to transfer arbitrary d-dimensional quantum states (known or unknown) between two superconducting transmon qudits coupled to a single cavity. The state transfer can be performed by employing resonant interactions only. In addition, quantum states can be deterministically transferred without measurement. Numerical simulations show that high-fidelity transfer of quantum states between two superconducting transmon qudits (d ≤ 5) is feasible with current circuit QED technology. This proposal is quite general and can be applied to accomplish the same task with natural or artificial atoms of a ladder-type level structure coupled to a cavity or resonator.

Strongly correlated superconductivity and quantum criticality

NASA Astrophysics Data System (ADS)

Tremblay, A.-M. S.

Doped Mott insulators and doped charge-transfer insulators describe classes of materials that can exhibit unconventional superconducting ground states. Examples include the cuprates and the layered organic superconductors of the BEDT family. I present results obtained from plaquette cellular dynamical mean-field theory. Continuous-time quantum Monte Carlo evaluation of the hybridization expansion allows one to study the models in the large interaction limit where quasiparticles can disappear. The normal state which is unstable to the superconducting state exhibits a first-order transition between a pseudogap and a correlated metal phase. That transition is the finite-doping extension of the metal-insulator transition obtained at half-filling. This transition serves as an organizing principle for the normal and superconducting states of both cuprates and doped organic superconductors. In the less strongly correlated limit, these methods also describe the more conventional case where the superconducting dome surrounds an antiferromagnetic quantum critical point. Sponsored by NSERC RGPIN-2014-04584, CIFAR, Research Chair in the Theory of Quantum Materials.

Coherent quantum phase slip.

PubMed

Astafiev, O V; Ioffe, L B; Kafanov, S; Pashkin, Yu A; Arutyunov, K Yu; Shahar, D; Cohen, O; Tsai, J S

2012-04-18

A hundred years after the discovery of superconductivity, one fundamental prediction of the theory, coherent quantum phase slip (CQPS), has not been observed. CQPS is a phenomenon exactly dual to the Josephson effect; whereas the latter is a coherent transfer of charges between superconducting leads, the former is a coherent transfer of vortices or fluxes across a superconducting wire. In contrast to previously reported observations of incoherent phase slip, CQPS has been only a subject of theoretical study. Its experimental demonstration is made difficult by quasiparticle dissipation due to gapless excitations in nanowires or in vortex cores. This difficulty might be overcome by using certain strongly disordered superconductors near the superconductor-insulator transition. Here we report direct observation of CQPS in a narrow segment of a superconducting loop made of strongly disordered indium oxide; the effect is made manifest through the superposition of quantum states with different numbers of flux quanta. As with the Josephson effect, our observation should lead to new applications in superconducting electronics and quantum metrology.

Thermal response of large area high temperature superconducting YBaCuO infrared bolometers

NASA Technical Reports Server (NTRS)

Khalil, Ali E.

1991-01-01

Thermal analysis of large area high temperature superconducting infrared detector operating in the equilibrium mode (bolometer) was performed. An expression for the temperature coefficient beta = 1/R(dR/dT) in terms of the thermal conductance and the thermal time constant of the detector were derived. A superconducting transition edge bolometer is a thermistor consisting of a thin film superconducting YBaCuO evaporated into a suitable thermally isolated substrate. The operating temperature of the bolometer is maintained close to the midpoint of the superconducting transition region where the resistance R has a maximum dynamic range. A detector with a strip configuration was analyzed and an expression for the temperature rise (delta T) above the ambient due to a uniform illumination with a source of power density was calculated. An expression for the thermal responsibility depends upon the spatial modulation frequency and the angular frequency of the incoming radiation. The problem of the thermal cross talk between different detector elements was addressed. In the case of monolithic HTS detector array with a row of square elements of dimensions 2a and CCD or CID readout electronics the thermal spread function was derived for different spacing between elements.

Toward a superconducting quantum computer. Harnessing macroscopic quantum coherence.

PubMed

Tsai, Jaw-Shen

2010-01-01

Intensive research on the construction of superconducting quantum computers has produced numerous important achievements. The quantum bit (qubit), based on the Josephson junction, is at the heart of this research. This macroscopic system has the ability to control quantum coherence. This article reviews the current state of quantum computing as well as its history, and discusses its future. Although progress has been rapid, the field remains beset with unsolved issues, and there are still many new research opportunities open to physicists and engineers.

Superconducting quantum circuits at the surface code threshold for fault tolerance.

PubMed

Barends, R; Kelly, J; Megrant, A; Veitia, A; Sank, D; Jeffrey, E; White, T C; Mutus, J; Fowler, A G; Campbell, B; Chen, Y; Chen, Z; Chiaro, B; Dunsworth, A; Neill, C; O'Malley, P; Roushan, P; Vainsencher, A; Wenner, J; Korotkov, A N; Cleland, A N; Martinis, John M

2014-04-24

A quantum computer can solve hard problems, such as prime factoring, database searching and quantum simulation, at the cost of needing to protect fragile quantum states from error. Quantum error correction provides this protection by distributing a logical state among many physical quantum bits (qubits) by means of quantum entanglement. Superconductivity is a useful phenomenon in this regard, because it allows the construction of large quantum circuits and is compatible with microfabrication. For superconducting qubits, the surface code approach to quantum computing is a natural choice for error correction, because it uses only nearest-neighbour coupling and rapidly cycled entangling gates. The gate fidelity requirements are modest: the per-step fidelity threshold is only about 99 per cent. Here we demonstrate a universal set of logic gates in a superconducting multi-qubit processor, achieving an average single-qubit gate fidelity of 99.92 per cent and a two-qubit gate fidelity of up to 99.4 per cent. This places Josephson quantum computing at the fault-tolerance threshold for surface code error correction. Our quantum processor is a first step towards the surface code, using five qubits arranged in a linear array with nearest-neighbour coupling. As a further demonstration, we construct a five-qubit Greenberger-Horne-Zeilinger state using the complete circuit and full set of gates. The results demonstrate that Josephson quantum computing is a high-fidelity technology, with a clear path to scaling up to large-scale, fault-tolerant quantum circuits.

A miniaturized 4 K platform for superconducting infrared photon counting detectors

NASA Astrophysics Data System (ADS)

Gemmell, Nathan R.; Hills, Matthew; Bradshaw, Tom; Rawlings, Tom; Green, Ben; Heath, Robert M.; Tsimvrakidis, Konstantinos; Dobrovolskiy, Sergiy; Zwiller, Val; Dorenbos, Sander N.; Crook, Martin; Hadfield, Robert H.

2017-11-01

We report on a miniaturized platform for superconducting infrared photon counting detectors. We have implemented a fibre-coupled superconducting nanowire single photon detector in a Stirling/Joule-Thomson platform with a base temperature of 4.2 K. We have verified a cooling power of 4 mW at 4.7 K. We report 20% system detection efficiency at 1310 nm wavelength at a dark count rate of 1 kHz. We have carried out compelling application demonstrations in single photon depth metrology and singlet oxygen luminescence detection.

Superconducting Detectors for Superlight Dark Matter.

PubMed

Hochberg, Yonit; Zhao, Yue; Zurek, Kathryn M

2016-01-08

We propose and study a new class of superconducting detectors that are sensitive to O(meV) electron recoils from dark matter-electron scattering. Such devices could detect dark matter as light as the warm dark-matter limit, m(X)≳1  keV. We compute the rate of dark-matter scattering off of free electrons in a (superconducting) metal, including the relevant Pauli blocking factors. We demonstrate that classes of dark matter consistent with terrestrial and cosmological or astrophysical constraints could be detected by such detectors with a moderate size exposure.

Superconducting Detectors for Superlight Dark Matter

NASA Astrophysics Data System (ADS)

Hochberg, Yonit; Zhao, Yue; Zurek, Kathryn M.

2016-01-01

We propose and study a new class of superconducting detectors that are sensitive to O (meV ) electron recoils from dark matter-electron scattering. Such devices could detect dark matter as light as the warm dark-matter limit, mX≳1 keV . We compute the rate of dark-matter scattering off of free electrons in a (superconducting) metal, including the relevant Pauli blocking factors. We demonstrate that classes of dark matter consistent with terrestrial and cosmological or astrophysical constraints could be detected by such detectors with a moderate size exposure.

Superconductivity and non-Fermi liquid behavior near a nematic quantum critical point.

PubMed

Lederer, Samuel; Schattner, Yoni; Berg, Erez; Kivelson, Steven A

2017-05-09

Using determinantal quantum Monte Carlo, we compute the properties of a lattice model with spin [Formula: see text] itinerant electrons tuned through a quantum phase transition to an Ising nematic phase. The nematic fluctuations induce superconductivity with a broad dome in the superconducting [Formula: see text] enclosing the nematic quantum critical point. For temperatures above [Formula: see text], we see strikingly non-Fermi liquid behavior, including a "nodal-antinodal dichotomy" reminiscent of that seen in several transition metal oxides. In addition, the critical fluctuations have a strong effect on the low-frequency optical conductivity, resulting in behavior consistent with "bad metal" phenomenology.

Integrated System Technologies for Modular Trapped Ion Quantum Information Processing

NASA Astrophysics Data System (ADS)

Crain, Stephen G.

Although trapped ion technology is well-suited for quantum information science, scalability of the system remains one of the main challenges. One of the challenges associated with scaling the ion trap quantum computer is the ability to individually manipulate the increasing number of qubits. Using micro-mirrors fabricated with micro-electromechanical systems (MEMS) technology, laser beams are focused on individual ions in a linear chain and steer the focal point in two dimensions. Multiple single qubit gates are demonstrated on trapped 171Yb+ qubits and the gate performance is characterized using quantum state tomography. The system features negligible crosstalk to neighboring ions (< 3e-4), and switching speeds comparable to typical single qubit gate times (< 2 mus). In a separate experiment, photons scattered from the 171Yb+ ion are coupled into an optical fiber with 63% efficiency using a high numerical aperture lens (0.6 NA). The coupled photons are directed to superconducting nanowire single photon detectors (SNSPD), which provide a higher detector efficiency (69%) compared to traditional photomultiplier tubes (35%). The total system photon collection efficiency is increased from 2.2% to 3.4%, which allows for fast state detection of the qubit. For a detection beam intensity of 11 mW/cm 2, the average detection time is 23.7 mus with 99.885(7)% detection fidelity. The technologies demonstrated in this thesis can be integrated to form a single quantum register with all of the necessary resources to perform local gates as well as high fidelity readout and provide a photon link to other systems.

Test of a Nb thin film superconducting detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lacquaniti, V.; Maggi, S.; Menichetti, E.

1993-08-01

Results from tests of several Nb thin film microstrip superconducting detectors are reported. A preliminary measurement of critical radius of the hot spot generated by 5 MeV [alpha]-particles is compared with simple model predictions.

Quantum-circuit refrigerator

NASA Astrophysics Data System (ADS)

Tan, Kuan Yen; Partanen, Matti; Lake, Russell E.; Govenius, Joonas; Masuda, Shumpei; Möttönen, Mikko

2017-05-01

Quantum technology promises revolutionizing applications in information processing, communications, sensing and modelling. However, efficient on-demand cooling of the functional quantum degrees of freedom remains challenging in many solid-state implementations, such as superconducting circuits. Here we demonstrate direct cooling of a superconducting resonator mode using voltage-controllable electron tunnelling in a nanoscale refrigerator. This result is revealed by a decreased electron temperature at a resonator-coupled probe resistor, even for an elevated electron temperature at the refrigerator. Our conclusions are verified by control experiments and by a good quantitative agreement between theory and experimental observations at various operation voltages and bath temperatures. In the future, we aim to remove spurious dissipation introduced by our refrigerator and to decrease the operational temperature. Such an ideal quantum-circuit refrigerator has potential applications in the initialization of quantum electric devices. In the superconducting quantum computer, for example, fast and accurate reset of the quantum memory is needed.

Hybrid Quantum Information Processing with Superconductors and Neutral Atoms

NASA Astrophysics Data System (ADS)

McDermott, Robert

Hybrid approaches to quantum information processing (QIP) aim to capitalize on the strengths of disparate quantum technologies to realize a system whose capabilities exceed those of any single experimental platform. At the University of Wisconsin, we are working toward integration of a fast superconducting quantum processor with a stable, long-lived quantum memory based on trapped neutral atoms. Here we describe the development of a quantum interface between superconducting thin-film cavity circuits and trapped Rydberg atoms, the key technological obstacle to realization of superconductor-atom hybrid QIP. Specific accomplishments to date include development of a theoretical protocol for high-fidelity state transfer between the atom and the cavity; fabrication and characterization of high- Q superconducting cavities with integrated trapping electrodes to enhance zero-point microwave fields at a location remote from the chip surface; and trapping and Rydberg excitation of single atoms within 1 mm of the cavity. We discuss the status of experiments to probe the strong coherent coupling of single Rydberg atoms and the superconducting cavity. Supported by ARO under contract W911NF-16-1-0133.

Rise time of voltage pulses in NbN superconducting single photon detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smirnov, K. V.; CJSC “Superconducting Nanotechnology”; National Research University Higher School of Economics, Moscow Institute of Electronics and Mathematics, 34 Tallinskaya St., 109028 Moscow

2016-08-01

We have found experimentally that the rise time of voltage pulse in NbN superconducting single photon detectors increases nonlinearly with increasing the length of the detector L. The effect is connected with dependence of resistance of the detector R{sub n}, which appears after photon absorption, on its kinetic inductance L{sub k} and, hence, on the length of the detector. This conclusion is confirmed by our calculations in the framework of two temperature model.

Fabrication of Circuit QED Quantum Processors, Part 1: Extensible Footprint for a Superconducting Surface Code

NASA Astrophysics Data System (ADS)

Bruno, A.; Michalak, D. J.; Poletto, S.; Clarke, J. S.; Dicarlo, L.

Large-scale quantum computation hinges on the ability to preserve and process quantum information with higher fidelity by increasing redundancy in a quantum error correction code. We present the realization of a scalable footprint for superconducting surface code based on planar circuit QED. We developed a tileable unit cell for surface code with all I/O routed vertically by means of superconducting through-silicon vias (TSVs). We address some of the challenges encountered during the fabrication and assembly of these chips, such as the quality of etch of the TSV, the uniformity of the ALD TiN coating conformal to the TSV, and the reliability of superconducting indium contact between the chips and PCB. We compare measured performance to a detailed list of specifications required for the realization of quantum fault tolerance. Our demonstration using centimeter-scale chips can accommodate the 50 qubits needed to target the experimental demonstration of small-distance logical qubits. Research funded by Intel Corporation and IARPA.

Realizing a partial general quantum cloning machine with superconducting quantum-interference devices in a cavity QED

NASA Astrophysics Data System (ADS)

Fang, Bao-Long; Yang, Zhen; Ye, Liu

2009-05-01

We propose a scheme for implementing a partial general quantum cloning machine with superconducting quantum-interference devices coupled to a nonresonant cavity. By regulating the time parameters, our system can perform optimal symmetric (asymmetric) universal quantum cloning, optimal symmetric (asymmetric) phase-covariant cloning, and optimal symmetric economical phase-covariant cloning. In the scheme the cavity is only virtually excited, thus, the cavity decay is suppressed during the cloning operations.

Proximity-Induced Superconductivity and Quantum Interference in Topological Crystalline Insulator SnTe Thin-Film Devices.

PubMed

Klett, Robin; Schönle, Joachim; Becker, Andreas; Dyck, Denis; Borisov, Kiril; Rott, Karsten; Ramermann, Daniela; Büker, Björn; Haskenhoff, Jan; Krieft, Jan; Hübner, Torsten; Reimer, Oliver; Shekhar, Chandra; Schmalhorst, Jan-Michael; Hütten, Andreas; Felser, Claudia; Wernsdorfer, Wolfgang; Reiss, Günter

2018-02-14

Topological crystalline insulators represent a new state of matter, in which the electronic transport is governed by mirror-symmetry protected Dirac surface states. Due to the helical spin-polarization of these surface states, the proximity of topological crystalline matter to a nearby superconductor is predicted to induce unconventional superconductivity and, thus, to host Majorana physics. We report on the preparation and characterization of Nb-based superconducting quantum interference devices patterned on top of topological crystalline insulator SnTe thin films. The SnTe films show weak anti-localization, and the weak links of the superconducting quantum interference devices (SQUID) exhibit fully gapped proximity-induced superconductivity. Both properties give a coinciding coherence length of 120 nm. The SQUID oscillations induced by a magnetic field show 2π periodicity, possibly dominated by the bulk conductivity.

Metal-insulator quantum critical point beneath the high Tc superconducting dome.

PubMed

Sebastian, Suchitra E; Harrison, N; Altarawneh, M M; Mielke, C H; Liang, Ruixing; Bonn, D A; Hardy, W N; Lonzarich, G G

2010-04-06

An enduring question in correlated systems concerns whether superconductivity is favored at a quantum critical point (QCP) characterized by a divergent quasiparticle effective mass. Despite such a scenario being widely postulated in high T(c) cuprates and invoked to explain non-Fermi liquid transport signatures, experimental evidence is lacking for a critical divergence under the superconducting dome. We use ultrastrong magnetic fields to measure quantum oscillations in underdoped YBa(2)Cu(3)O(6+x), revealing a dramatic doping-dependent upturn in quasiparticle effective mass at a critical metal-insulator transition beneath the superconducting dome. Given the location of this QCP under a plateau in T(c) in addition to a postulated QCP at optimal doping, we discuss the intriguing possibility of two intersecting superconducting subdomes, each centered at a critical Fermi surface instability.

Evaluating charge noise acting on semiconductor quantum dots in the circuit quantum electrodynamics architecture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Basset, J.; Stockklauser, A.; Jarausch, D.-D.

2014-08-11

We evaluate the charge noise acting on a GaAs/GaAlAs based semiconductor double quantum dot dipole-coupled to the voltage oscillations of a superconducting transmission line resonator. The in-phase (I) and the quadrature (Q) components of the microwave tone transmitted through the resonator are sensitive to charging events in the surrounding environment of the double dot with an optimum sensitivity of 8.5×10{sup −5} e/√(Hz). A low frequency 1/f type noise spectrum combined with a white noise level of 6.6×10{sup −6} e{sup 2}/Hz above 1 Hz is extracted, consistent with previous results obtained with quantum point contact charge detectors on similar heterostructures. The slope ofmore » the 1/f noise allows to extract a lower bound for the double-dot charge qubit dephasing rate which we compare to the one extracted from a Jaynes-Cummings Hamiltonian approach. The two rates are found to be similar emphasizing that charge noise is the main source of dephasing in our system.« less

Significant-Loophole-Free Test of Bell's Theorem with Entangled Photons.

PubMed

Giustina, Marissa; Versteegh, Marijn A M; Wengerowsky, Sören; Handsteiner, Johannes; Hochrainer, Armin; Phelan, Kevin; Steinlechner, Fabian; Kofler, Johannes; Larsson, Jan-Åke; Abellán, Carlos; Amaya, Waldimar; Pruneri, Valerio; Mitchell, Morgan W; Beyer, Jörn; Gerrits, Thomas; Lita, Adriana E; Shalm, Lynden K; Nam, Sae Woo; Scheidl, Thomas; Ursin, Rupert; Wittmann, Bernhard; Zeilinger, Anton

2015-12-18

Local realism is the worldview in which physical properties of objects exist independently of measurement and where physical influences cannot travel faster than the speed of light. Bell's theorem states that this worldview is incompatible with the predictions of quantum mechanics, as is expressed in Bell's inequalities. Previous experiments convincingly supported the quantum predictions. Yet, every experiment requires assumptions that provide loopholes for a local realist explanation. Here, we report a Bell test that closes the most significant of these loopholes simultaneously. Using a well-optimized source of entangled photons, rapid setting generation, and highly efficient superconducting detectors, we observe a violation of a Bell inequality with high statistical significance. The purely statistical probability of our results to occur under local realism does not exceed 3.74×10^{-31}, corresponding to an 11.5 standard deviation effect.

Quantum fluctuations of the superconducting cosmic string

NASA Technical Reports Server (NTRS)

Zhang, Shoucheng

1987-01-01

Quantum fluctuations of the proposed superconducting string with Bose charge carriers are studied in terms of the vortices on the string world sheet. In the thermodynamical limit, it is found that they appear in the form of free vortices rather than as bound pairs. This fluctuation mode violates the topological conservation law on which superconductivity is based. However, this limit may not be reached. The critical size of the superconducting string is estimated as a function of the coupling constants involved.

Correlation effects in superconducting quantum dot systems

NASA Astrophysics Data System (ADS)

Pokorný, Vladislav; Žonda, Martin

2018-05-01

We study the effect of electron correlations on a system consisting of a single-level quantum dot with local Coulomb interaction attached to two superconducting leads. We use the single-impurity Anderson model with BCS superconducting baths to study the interplay between the proximity induced electron pairing and the local Coulomb interaction. We show how to solve the model using the continuous-time hybridization-expansion quantum Monte Carlo method. The results obtained for experimentally relevant parameters are compared with results of self-consistent second order perturbation theory as well as with the numerical renormalization group method.

Tuning single-photon sources for telecom multi-photon experiments.

PubMed

Greganti, Chiara; Schiansky, Peter; Calafell, Irati Alonso; Procopio, Lorenzo M; Rozema, Lee A; Walther, Philip

2018-02-05

Multi-photon state generation is of great interest for near-future quantum simulation and quantum computation experiments. To-date spontaneous parametric down-conversion is still the most promising process, even though two major impediments still exist: accidental photon noise (caused by the probabilistic non-linear process) and imperfect single-photon purity (arising from spectral entanglement between the photon pairs). In this work, we overcome both of these difficulties by (1) exploiting a passive temporal multiplexing scheme and (2) carefully optimizing the spectral properties of the down-converted photons using periodically-poled KTP crystals. We construct two down-conversion sources in the telecom wavelength regime, finding spectral purities of > 91%, while maintaining high four-photon count rates. We use single-photon grating spectrometers together with superconducting nanowire single-photon detectors to perform a detailed characterization of our multi-photon source. Our methods provide practical solutions to produce high-quality multi-photon states, which are in demand for many quantum photonics applications.

Langmuir vacuum and superconductivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veklenko, B. A.

It is shown that, in the 'jelly' model of cold electron-ion plasma, the interaction between electrons and the quantum electromagnetic vacuum of Langmuir waves involves plasma superconductivity with an energy gap proportional to the energy of the Langmuir quantum.

Equal-Spin Andreev Reflection on Junctions of Spin-Resolved Quantum Hall Bulk State and Spin-Singlet Superconductor.

PubMed

Matsuo, Sadashige; Ueda, Kento; Baba, Shoji; Kamata, Hiroshi; Tateno, Mizuki; Shabani, Javad; Palmstrøm, Christopher J; Tarucha, Seigo

2018-02-22

The recent development of superconducting spintronics has revealed the spin-triplet superconducting proximity effect from a spin-singlet superconductor into a spin-polarized normal metal. In addition recently superconducting junctions using semiconductors are in demand for highly controlled experiments to engineer topological superconductivity. Here we report experimental observation of Andreev reflection in junctions of spin-resolved quantum Hall (QH) states in an InAs quantum well and the spin-singlet superconductor NbTi. The measured conductance indicates a sub-gap feature and two peaks on the outer side of the sub-gap feature in the QH plateau-transition regime increases. The observed structures can be explained by considering transport with Andreev reflection from two channels, one originating from equal-spin Andreev reflection intermediated by spin-flip processes and second arising from normal Andreev reflection. This result indicates the possibility to induce the superconducting proximity gap in the the QH bulk state, and the possibility for the development of superconducting spintronics in semiconductor devices.

Andreev molecules in semiconductor nanowire double quantum dots.

PubMed

Su, Zhaoen; Tacla, Alexandre B; Hocevar, Moïra; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P A M; Daley, Andrew J; Pekker, David; Frolov, Sergey M

2017-09-19

Chains of quantum dots coupled to superconductors are promising for the realization of the Kitaev model of a topological superconductor. While individual superconducting quantum dots have been explored, control of longer chains requires understanding of interdot coupling. Here, double quantum dots are defined by gate voltages in indium antimonide nanowires. High transparency superconducting niobium titanium nitride contacts are made to each of the dots in order to induce superconductivity, as well as probe electron transport. Andreev bound states induced on each of dots hybridize to define Andreev molecular states. The evolution of these states is studied as a function of charge parity on the dots, and in magnetic field. The experiments are found in agreement with a numerical model.Quantum dots in a nanowire are one possible approach to creating a solid-state quantum simulator. Here, the authors demonstrate the coupling of electronic states in a double quantum dot to form Andreev molecule states; a potential building block for longer chains suitable for quantum simulation.

Toward a superconducting quantum computer

PubMed Central

Tsai, Jaw-Shen

2010-01-01

Intensive research on the construction of superconducting quantum computers has produced numerous important achievements. The quantum bit (qubit), based on the Josephson junction, is at the heart of this research. This macroscopic system has the ability to control quantum coherence. This article reviews the current state of quantum computing as well as its history, and discusses its future. Although progress has been rapid, the field remains beset with unsolved issues, and there are still many new research opportunities open to physicists and engineers. PMID:20431256

Implementing two optimal economical quantum cloning with superconducting quantum interference devices in a cavity

NASA Astrophysics Data System (ADS)

Ye, Liu; Hu, GuiYu; Li, AiXia

2011-01-01

We propose a unified scheme to implement the optimal 1 → 3 economical phase-covariant quantum cloning and optimal 1 → 3 economical real state cloning with superconducting quantum interference devices (SQUIDs) in a cavity. During this process, no transfer of quantum information between the SQUIDs and cavity is required. The cavity field is only virtually excited. The scheme is insensitive to cavity decay. Therefore, the scheme can be experimentally realized in the range of current cavity QED techniques.

The Physics of Superconducting Microwave Resonators

NASA Astrophysics Data System (ADS)

Gao, Jiansong

Over the past decade, low temperature detectors have brought astronomers revolutionary new observational capabilities and led to many great discoveries. Although a single low temperature detector has very impressive sensitivity, a large detector array would be much more powerful and are highly demanded for the study of more difficult and fundamental problems in astronomy. However, current detector technologies, such as transition edge sensors and superconducting tunnel junction detectors, are difficult to integrate into a large array. The microwave kinetic inductance detector (MKID) is a promising new detector technology invented at Caltech and JPL which provides both high sensitivity and an easy solution to the detector integration. It senses the change in the surface impedance of a superconductor as incoming photons break Cooper pairs, by using high-Q superconducting microwave resonators capacitively coupled to a common feedline. This architecture allows thousands of detectors to be easily integrated through passive frequency domain multiplexing. In this thesis, we explore the rich and interesting physics behind these superconducting microwave resonators. The first part of the thesis discusses the surface impedance of a superconductor, the kinetic inductance of a superconducting coplanar waveguide, and the circuit response of a resonator. These topics are related with the responsivity of MKIDs. The second part presents the study of the excess frequency noise that is universally observed in these resonators. The properties of the excess noise, including power, temperature, material, and geometry dependence, have been quantified. The noise source has been identified to be the two-level systems in the dielectric material on the surface of the resonator. A semi-empirical noise model has been developed to explain the power and geometry dependence of the noise, which is useful to predict the noise for a specified resonator geometry. The detailed physical noise mechanism, however, is still not clear. With the theoretical results of the responsivity and the semi-empirical noise model established in this thesis, a prediction of the detector sensitivity (noise equivalent power) and an optimization of the detector design are now possible.

Microwave amplification with nanomechanical resonators.

PubMed

Massel, F; Heikkilä, T T; Pirkkalainen, J-M; Cho, S U; Saloniemi, H; Hakonen, P J; Sillanpää, M A

2011-12-14

The sensitive measurement of electrical signals is at the heart of modern technology. According to the principles of quantum mechanics, any detector or amplifier necessarily adds a certain amount of noise to the signal, equal to at least the noise added by quantum fluctuations. This quantum limit of added noise has nearly been reached in superconducting devices that take advantage of nonlinearities in Josephson junctions. Here we introduce the concept of the amplification of microwave signals using mechanical oscillation, which seems likely to enable quantum-limited operation. We drive a nanomechanical resonator with a radiation pressure force, and provide an experimental demonstration and an analytical description of how a signal input to a microwave cavity induces coherent stimulated emission and, consequently, signal amplification. This generic scheme, which is based on two linear oscillators, has the advantage of being conceptually and practically simpler than the Josephson junction devices. In our device, we achieve signal amplification of 25 decibels with the addition of 20 quanta of noise, which is consistent with the expected amount of added noise. The generality of the model allows for realization in other physical systems as well, and we anticipate that near-quantum-limited mechanical microwave amplification will soon be feasible in various applications involving integrated electrical circuits.

Superconducting transition detectors for low-energy gamma-ray astrophysics

NASA Astrophysics Data System (ADS)

Kurfess, J. D.; Johnson, W. N.; Fritz, G. G.; Strickman, M. S.; Kinzer, R. L.; Jung, G.; Drukier, A. K.; Chmielowski, M.

1990-08-01

A program to investigate superconducting devices such as STDs for use in high-resolution Compton telescopes and coded-aperture detectors is presented. For higher energy applications, techniques are investigated with potential for scaling to large detectors, while also providing excellent energy and positional resolution. STDs are discussed, utilizing a uniform array of spherical granules tens of microns in diameter. The typical temperature-magnetic field phase for a low-temperature superconductor, the signal produced by the superconducting-normal transition in the 32-m diameter Sn granule, and the temperature history of an STD granule following heating by an ionizing particle are illustrated.

Environmental testing of high Tc superconductive thermal isolators for space-borne cryogenic detector systems

NASA Technical Reports Server (NTRS)

Wise, Stephanie A.; Buckley, John D.; Randolf, Henry W.; Verbelyi, Darren; Haertling, Gene H.; Hooker, Matthew W.; Selim, Raouf; Caton, Randall

1992-01-01

Thick films of superconductive material on low thermal conductivity substrates (e.g., yttria-stabilized zirconia and fused silica) are considered as a replacement for the existing electrical connections between the detector array and data acquisition and storage electronics in the cryogenic detector systems being developed by NASA. The paper describes some of the design constraints on the superconducting device and presents results of a preliminary analysis of the effects of vibration, gamma irradiation, and long-term exposure to high vacuum and liquid nitrogen encountered in operating such a device in space.

Edge-mode superconductivity in a two-dimensional topological insulator.

PubMed

Pribiag, Vlad S; Beukman, Arjan J A; Qu, Fanming; Cassidy, Maja C; Charpentier, Christophe; Wegscheider, Werner; Kouwenhoven, Leo P

2015-07-01

Topological superconductivity is an exotic state of matter that supports Majorana zero-modes, which have been predicted to occur in the surface states of three-dimensional systems, in the edge states of two-dimensional systems, and in one-dimensional wires. Localized Majorana zero-modes obey non-Abelian exchange statistics, making them interesting building blocks for topological quantum computing. Here, we report superconductivity induced in the edge modes of semiconducting InAs/GaSb quantum wells, a two-dimensional topological insulator. Using superconducting quantum interference we demonstrate gate-tuning between edge-dominated and bulk-dominated regimes of superconducting transport. The edge-dominated regime arises only under conditions of high-bulk resistivity, which we associate with the two-dimensional topological phase. These experiments establish InAs/GaSb as a promising platform for the confinement of Majoranas into localized states, enabling future investigations of non-Abelian statistics.

On-chip quantum interference of a superconducting microsphere

NASA Astrophysics Data System (ADS)

Pino, H.; Prat-Camps, J.; Sinha, K.; Prasanna Venkatesh, B.; Romero-Isart, O.

2018-04-01

We propose and analyze an all-magnetic scheme to perform a Young’s double slit experiment with a micron-sized superconducting sphere of mass ≳ {10}13 amu. We show that its center of mass could be prepared in a spatial quantum superposition state with an extent of the order of half a micrometer. The scheme is based on magnetically levitating the sphere above a superconducting chip and letting it skate through a static magnetic potential landscape where it interacts for short intervals with quantum circuits. In this way, a protocol for fast quantum interferometry using quantum magnetomechanics is passively implemented. Such a table-top earth-based quantum experiment would operate in a parameter regime where gravitational energy scales become relevant. In particular, we show that the faint parameter-free gravitationally-induced decoherence collapse model, proposed by Diósi and Penrose, could be unambiguously falsified.

Radiofrequency amplifier based on a dc superconducting quantum interference device

DOEpatents

Hilbert, C.; Martinis, J.M.; Clarke, J.

1984-04-27

A low noise radiofrequency amplifer, using a dc SQUID (superconducting quantum interference device) as the input amplifying element. The dc SQUID and an input coil are maintained at superconductivity temperatures in a superconducting shield, with the input coil inductively coupled to the superconducting ring of the dc SQUID. A radiofrequency signal from outside the shield is applied to the input coil, and an amplified radiofrequency signal is developed across the dc SQUID ring and transmitted to exteriorly of the shield. A power gain of 19.5 +- 0.5 dB has been achieved with a noise temperature of 1.0 +- 0.4 K at a frequency of 100 MHz.

Superconducting inductive displacement detection of a microcantilever

NASA Astrophysics Data System (ADS)

Vinante, A.

2014-07-01

We demonstrate a superconducting inductive technique to measure the displacement of a micromechanical resonator. In our scheme, a type I superconducting microsphere is attached to the free end of a microcantilever and approached to the loop of a dc Superconducting Quantum Interference Device (SQUID) microsusceptometer. A local magnetic field as low as 100 μT, generated by a field coil concentric to the SQUID, enables detection of the cantilever thermomechanical noise at 4.2 K. The magnetomechanical coupling and the magnetic spring are in good agreement with image method calculations assuming pure Meissner effect. These measurements are relevant to recent proposals of quantum magnetomechanics experiments based on levitating superconducting microparticles.

Highly efficient entanglement swapping and teleportation at telecom wavelength

PubMed Central

Jin, Rui-Bo; Takeoka, Masahiro; Takagi, Utako; Shimizu, Ryosuke; Sasaki, Masahide

2015-01-01

Entanglement swapping at telecom wavelengths is at the heart of quantum networking in optical fiber infrastructures. Although entanglement swapping has been demonstrated experimentally so far using various types of entangled photon sources both in near-infrared and telecom wavelength regions, the rate of swapping operation has been too low to be applied to practical quantum protocols, due to limited efficiency of entangled photon sources and photon detectors. Here we demonstrate drastic improvement of the efficiency at telecom wavelength by using two ultra-bright entangled photon sources and four highly efficient superconducting nanowire single photon detectors. We have attained a four-fold coincidence count rate of 108 counts per second, which is three orders higher than the previous experiments at telecom wavelengths. A raw (net) visibility in a Hong-Ou-Mandel interference between the two independent entangled sources was 73.3 ± 1.0% (85.1 ± 0.8%). We performed the teleportation and entanglement swapping, and obtained a fidelity of 76.3% in the swapping test. Our results on the coincidence count rates are comparable with the ones ever recorded in teleportation/swapping and multi-photon entanglement generation experiments at around 800 nm wavelengths. Our setup opens the way to practical implementation of device-independent quantum key distribution and its distance extension by the entanglement swapping as well as multi-photon entangled state generation in telecom band infrastructures with both space and fiber links. PMID:25791212

Highly efficient entanglement swapping and teleportation at telecom wavelength.

PubMed

Jin, Rui-Bo; Takeoka, Masahiro; Takagi, Utako; Shimizu, Ryosuke; Sasaki, Masahide

2015-03-20

Entanglement swapping at telecom wavelengths is at the heart of quantum networking in optical fiber infrastructures. Although entanglement swapping has been demonstrated experimentally so far using various types of entangled photon sources both in near-infrared and telecom wavelength regions, the rate of swapping operation has been too low to be applied to practical quantum protocols, due to limited efficiency of entangled photon sources and photon detectors. Here we demonstrate drastic improvement of the efficiency at telecom wavelength by using two ultra-bright entangled photon sources and four highly efficient superconducting nanowire single photon detectors. We have attained a four-fold coincidence count rate of 108 counts per second, which is three orders higher than the previous experiments at telecom wavelengths. A raw (net) visibility in a Hong-Ou-Mandel interference between the two independent entangled sources was 73.3 ± 1.0% (85.1 ± 0.8%). We performed the teleportation and entanglement swapping, and obtained a fidelity of 76.3% in the swapping test. Our results on the coincidence count rates are comparable with the ones ever recorded in teleportation/swapping and multi-photon entanglement generation experiments at around 800 nm wavelengths. Our setup opens the way to practical implementation of device-independent quantum key distribution and its distance extension by the entanglement swapping as well as multi-photon entangled state generation in telecom band infrastructures with both space and fiber links.

Proceedings of the Annual Conference on Magnetism and Magnetic Materials (38th) Held at Minneapolis, Minnesota on 15-18 November 1993. (Journal of Applied Physics. Volume 75, Number 10, Part 28

DTIC Science & Technology

1994-05-15

Nogues superconducting quantum interference device magnetometry and small-angle neutron-scattering techniques 5829 Thermodynamical properties of a...sa’nple magnetometer (VSM) and superconducting Coey et al.1 have been extensively studied during the past quantum interference device (SQUID) were used to...were measured in a superconducting quantum- interference 30 device magnetometer at 273 K. 20 e 10 U1 Y3 U RESULTS - C0 20 40 60 80 100 Phase relations

Nano-patterned superconducting surface for high quantum efficiency cathode

DOEpatents

Hannon, Fay; Musumeci, Pietro

2017-03-07

A method for providing a superconducting surface on a laser-driven niobium cathode in order to increase the effective quantum efficiency. The enhanced surface increases the effective quantum efficiency by improving the laser absorption of the surface and enhancing the local electric field. The surface preparation method makes feasible the construction of superconducting radio frequency injectors with niobium as the photocathode. An array of nano-structures are provided on a flat surface of niobium. The nano-structures are dimensionally tailored to interact with a laser of specific wavelength to thereby increase the electron yield of the surface.

Control and Measurement of an Xmon with the Quantum Socket

NASA Astrophysics Data System (ADS)

McConkey, T. G.; Bejanin, J. H.; Earnest, C. T.; McRae, C. R. H.; Rinehart, J. R.; Weides, M.; Mariantoni, M.

The implementation of superconducting quantum processors is rapidly reaching scalability limitations. Extensible electronics and wiring solutions for superconducting quantum bits (qubits) are among the most imminent issues to be tackled. The necessity to substitute planar electrical interconnects (e.g., wire bonds) with three-dimensional wires is emerging as a fundamental pillar towards scalability. In a previous work, we have shown that three-dimensional wires housed in a suitable package, named the quantum socket, can be utilized to measure high-quality superconducting resonators. In this work, we set out to test the quantum socket with actual superconducting qubits to verify its suitability as a wiring solution in the development of an extensible quantum computing architecture. To this end, we have designed and fabricated a series of Xmon qubits. The qubits range in frequency from about 6 to 7 GHz with anharmonicity of 200 MHz and can be tuned by means of Z pulses. Controlling tunable Xmons will allow us to verify whether the three-dimensional wires contact resistance is low enough for qubit operation. Qubit T1 and T2 times and single qubit gate fidelities are compared against current standards in the field.

Quantum memory operations in a flux qubit - spin ensemble hybrid system

NASA Astrophysics Data System (ADS)

Saito, S.; Zhu, X.; Amsuss, R.; Matsuzaki, Y.; Kakuyanagi, K.; Shimo-Oka, T.; Mizuochi, N.; Nemoto, K.; Munro, W. J.; Semba, K.

2014-03-01

Superconducting quantum bits (qubits) are one of the most promising candidates for a future large-scale quantum processor. However for larger scale realizations the currently reported coherence times of these macroscopic objects (superconducting qubits) has not yet reached those of microscopic systems (electron spins, nuclear spins, etc). In this context, a superconductor-spin ensemble hybrid system has attracted considerable attention. The spin ensemble could operate as a quantum memory for superconducting qubits. We have experimentally demonstrated quantum memory operations in a superconductor-diamond hybrid system. An excited state and a superposition state prepared in the flux qubit can be transferred to, stored in and retrieved from the NV spin ensemble in diamond. From these experiments, we have found the coherence time of the spin ensemble is limited by the inhomogeneous broadening of the electron spin (4.4 MHz) and by the hyperfine coupling to nitrogen nuclear spins (2.3 MHz). In the future, spin echo techniques could eliminate these effects and elongate the coherence time. Our results are a significant first step in utilizing the spin ensemble as long-lived quantum memory for superconducting flux qubits. This work was supported by the FIRST program and NICT.

Terahertz Mixing Characteristics of NbN Superconducting Tunnel Junctions and Related Astronomical Observations

NASA Astrophysics Data System (ADS)

Li, J.

2010-01-01

High-sensitivity superconducting SIS (superconductor-insulator-superconductor) mixers are playing an increasingly important role in the terahertz (THz) astronomical observation, which is an emerging research frontier in modern astrophysics. Superconducting SIS mixers with niobium (Nb) tunnel junctions have reached a sensitivity close to the quantum limit, but have a frequency limit about 0.7 THz (i.e., gap frequency of Nb tunnel junctions). Beyond this frequency Nb superconducting films will absorb energetic photons (i.e., energy loss) to break Cooper pairs, thereby resulting in significant degradation of the mixer performance. Therefore, it is of particular interest to develop THz superconducting SIS mixers incorporating tunnel junctions with a larger energy gap. Niobium-nitride (NbN) superconducting tunnel junctions have been long known for their large energy gap, almost double that of Nb ones. With the introduction of epitaxially grown NbN films, the fabrication technology of NbN superconducting tunnel junctions has been considerably improved in the recent years. Nevertheless, their performances are still not as good as Nb ones, and furthermore they are not yet demonstrated in real astronomical applications. Given the facts mentioned above, in this paper we systematically study the quantum mixing behaviors of NbN superconducting tunnel junctions in the THz regime and demonstrate an astronomical testing observation with a 0.5 THz superconducting SIS mixer developed with NbN tunnel junctions. The main results of this study include: (1) successful design and fabrication of a 0.4˜0.6 THz waveguide mixing circuit with the high-dielectric-constant MgO substrate; (2) successful fabrication of NbN superconducting tunnel junctions with the gap voltage reaching 5.6 mV and the quality factor as high as 15; (3) demonstration of a 0.5 THz waveguide NbN superconducting SIS mixer with a measured receiver noise temperature (no correction) as low as five times the quantum limit (5hω/kB), which is the best among NbN superconducting SIS mixers developed in this frequency band; (4) demonstration of high sensitivity for NbN superconducting SIS mixers operated at temperatures as high as 10 K, and demonstration of much less interference resulting from the Josephson effect; (5) demonstration of the first astronomical observation ever done with an NbN superconducting SIS mixer. This study has provided further understanding of the quantum mixing behaviors of NbN superconducting SIS mixers. It has been demonstrated that NbN superconducting SIS mixers can reach nearly quantum-limited sensitivity and have good stability. Furthermore, NbN superconducting SIS mixers have less stringent requirement for cooling and magnetic field compared with Nb ones. Hence they can be used in astronomical applications, especially for space-borne projects and complex systems such as multi-beam receivers.

Memorial to Professor Antonio Barone

NASA Astrophysics Data System (ADS)

Tafuri, Francesco; Pepe, Giampiero; Vaglio, Ruggero

2014-04-01

Antonio Barone prematurely passed away on 4 December 2011 at the age of 72, after a one-year battle with cancer. He left behind his wife Sveva and his two sons, Alberto and Livio. Antonio was Professor Emeritus at the University of Napoli Federico II, where he had been teaching for about 40 years. The initial research activity of Antonio was in the field of nuclear physics. In this context, almost 45 years ago, the Ge 'Lithium drift' semiconductor detectors represented a novelty, due to the high energy resolution enabled by those devices. Superconductors stimulated new approaches to radiation detection and this motivated Antonio's interest towards superconductivity. Following the birth of the Laboratorio di Cibernetica of the CNR in 1967 he was given the opportunity to work on a joint USA-Italy project (University of Wisconsin, Madison and CNR Naples) in the field of superconductivity on the peculiar subject of the superconductive 'Neuristors'. His research activity on Josephson junctions opened up a wide variety of very stimulating subjects in which he was deeply involved, ranging from the soliton propagation in 'long' Josephson structures to fluctuations phenomena, from light-sensitive junctions and proximity effect to the development of innovative superconducting devices. The strong interaction of Antonio with the Landau Institute for Theoretical Physics of the Academy of Sciences in Moscow, characterizes a long period of his research activity with a precious merging of theoretical and experimental aspects. This body of work converged into the famous monograph on the 'Physics and Applications of the Josephson Effect', written in collaboration with Gianfranco Paternò in 1982. This rapidly became the reference text for the Josephson effect, as documented by thousands of citations and the fact that it was translated into Russian, Japanese and Chinese. In 1983 Antonio was awarded the highest academic title of 'Doctor of the Physical-Mathematical Sciences' by the Academy of Sciences in Moscow, and later the coveted Kapitza Prize. The discovery of high-Tc superconductors (HTS) offered new problems and perspectives. Antonio and his group significantly contributed by reporting original results on the 'archetype' high-Tc Josephson junctions. His studies on unconventional superconductivity, first developed for 'p-wave' superconductors, had great impact and were very influential on the d-wave experiments on HTS compounds, and later on the physics of HTS Josephson junctions. Macroscopic quantum phenomena and particle detectors are the keywords and the logical paths to recall several relevant contributions from Antonio scattered over more than 40 years of activity. Topics of his interest ranged from the fundamentals of macroscopic quantum tunnelling to barrier penetration in non stationary fields, to finally a project encompassing a wider vision of macroscopic quantum phenomena in unconventional systems. He has filled very important positions of scientific management in Italy and participated in many international committees. He chaired (with R Vaglio) the very successful EUCAS 2003 conference in Sorrento, Italy. He has significantly contributed to the popularization of superconductivity as a professor, as a researcher and as a manager. All scientists that had the privilege to deal with him remember Antonio as a real gentleman of science and life, a man of vision and perspective. The local Organizing Committee and the International Advisory Committee of EUCAS 2013 have dedicated the Session 'Junctions and Squids' to the memory of Professor Antonio Barone1. 1A longer version of this memorial has also been published on the Istituto SPIN-CNR website (www.spin.cnr.it/index.php/barone).

Inverse correlation between quasiparticle mass and T c in a cuprate high-T c superconductor.

PubMed

Putzke, Carsten; Malone, Liam; Badoux, Sven; Vignolle, Baptiste; Vignolles, David; Tabis, Wojciech; Walmsley, Philip; Bird, Matthew; Hussey, Nigel E; Proust, Cyril; Carrington, Antony

2016-03-01

Close to a zero-temperature transition between ordered and disordered electronic phases, quantum fluctuations can lead to a strong enhancement of electron mass and to the emergence of competing phases such as superconductivity. A correlation between the existence of such a quantum phase transition and superconductivity is quite well established in some heavy fermion and iron-based superconductors, and there have been suggestions that high-temperature superconductivity in copper-oxide materials (cuprates) may also be driven by the same mechanism. Close to optimal doping, where the superconducting transition temperature T c is maximal in cuprates, two different phases are known to compete with superconductivity: a poorly understood pseudogap phase and a charge-ordered phase. Recent experiments have shown a strong increase in quasiparticle mass m* in the cuprate YBa2Cu3O7-δ as optimal doping is approached, suggesting that quantum fluctuations of the charge-ordered phase may be responsible for the high-T c superconductivity. We have tested the robustness of this correlation between m* and T c by performing quantum oscillation studies on the stoichiometric compound YBa2Cu4O8 under hydrostatic pressure. In contrast to the results for YBa2Cu3O7-δ, we find that in YBa2Cu4O8, the mass decreases as T c increases under pressure. This inverse correlation between m* and T c suggests that quantum fluctuations of the charge order enhance m* but do not enhance T c.

Inverse correlation between quasiparticle mass and Tc in a cuprate high-Tc superconductor

PubMed Central

Putzke, Carsten; Malone, Liam; Badoux, Sven; Vignolle, Baptiste; Vignolles, David; Tabis, Wojciech; Walmsley, Philip; Bird, Matthew; Hussey, Nigel E.; Proust, Cyril; Carrington, Antony

2016-01-01

Close to a zero-temperature transition between ordered and disordered electronic phases, quantum fluctuations can lead to a strong enhancement of electron mass and to the emergence of competing phases such as superconductivity. A correlation between the existence of such a quantum phase transition and superconductivity is quite well established in some heavy fermion and iron-based superconductors, and there have been suggestions that high-temperature superconductivity in copper-oxide materials (cuprates) may also be driven by the same mechanism. Close to optimal doping, where the superconducting transition temperature Tc is maximal in cuprates, two different phases are known to compete with superconductivity: a poorly understood pseudogap phase and a charge-ordered phase. Recent experiments have shown a strong increase in quasiparticle mass m* in the cuprate YBa2Cu3O7-δ as optimal doping is approached, suggesting that quantum fluctuations of the charge-ordered phase may be responsible for the high-Tc superconductivity. We have tested the robustness of this correlation between m* and Tc by performing quantum oscillation studies on the stoichiometric compound YBa2Cu4O8 under hydrostatic pressure. In contrast to the results for YBa2Cu3O7-δ, we find that in YBa2Cu4O8, the mass decreases as Tc increases under pressure. This inverse correlation between m* and Tc suggests that quantum fluctuations of the charge order enhance m* but do not enhance Tc. PMID:27034989

Digital-analog quantum simulation of generalized Dicke models with superconducting circuits

NASA Astrophysics Data System (ADS)

Lamata, Lucas

2017-03-01

We propose a digital-analog quantum simulation of generalized Dicke models with superconducting circuits, including Fermi- Bose condensates, biased and pulsed Dicke models, for all regimes of light-matter coupling. We encode these classes of problems in a set of superconducting qubits coupled with a bosonic mode implemented by a transmission line resonator. Via digital-analog techniques, an efficient quantum simulation can be performed in state-of-the-art circuit quantum electrodynamics platforms, by suitable decomposition into analog qubit-bosonic blocks and collective single-qubit pulses through digital steps. Moreover, just a single global analog block would be needed during the whole protocol in most of the cases, superimposed with fast periodic pulses to rotate and detune the qubits. Therefore, a large number of digital steps may be attained with this approach, providing a reduced digital error. Additionally, the number of gates per digital step does not grow with the number of qubits, rendering the simulation efficient. This strategy paves the way for the scalable digital-analog quantum simulation of many-body dynamics involving bosonic modes and spin degrees of freedom with superconducting circuits.

Digital-analog quantum simulation of generalized Dicke models with superconducting circuits

PubMed Central

Lamata, Lucas

2017-01-01

We propose a digital-analog quantum simulation of generalized Dicke models with superconducting circuits, including Fermi- Bose condensates, biased and pulsed Dicke models, for all regimes of light-matter coupling. We encode these classes of problems in a set of superconducting qubits coupled with a bosonic mode implemented by a transmission line resonator. Via digital-analog techniques, an efficient quantum simulation can be performed in state-of-the-art circuit quantum electrodynamics platforms, by suitable decomposition into analog qubit-bosonic blocks and collective single-qubit pulses through digital steps. Moreover, just a single global analog block would be needed during the whole protocol in most of the cases, superimposed with fast periodic pulses to rotate and detune the qubits. Therefore, a large number of digital steps may be attained with this approach, providing a reduced digital error. Additionally, the number of gates per digital step does not grow with the number of qubits, rendering the simulation efficient. This strategy paves the way for the scalable digital-analog quantum simulation of many-body dynamics involving bosonic modes and spin degrees of freedom with superconducting circuits. PMID:28256559

The Microwave SQUID Multiplexer

NASA Astrophysics Data System (ADS)

Mates, John Arthur Benson

2011-12-01

This thesis describes a multiplexer of Superconducting Quantum Interference Devices (SQUIDs) with low-noise, ultra-low power dissipation, and great scalability. The multiplexer circuit measures the magnetic flux in a large number of unshunted rf SQUIDs by coupling each SQUID to a superconducting microwave resonator tuned to a unique resonance frequency and driving the resonators from a common feedline. A superposition of microwave tones measures each SQUID simultaneously using only two coaxial cables between the cryogenic device and room temperature. This multiplexer will enable the instrumentation of arrays with hundreds of thousands of low-temperature detectors for new applications in cosmology, materials analysis, and nuclear non-proliferation. The driving application of the Microwave SQUID Multiplexer is the readout of large arrays of superconducting transition-edge sensors, by some figures of merit the most sensitive detectors of electromagnetic signals over a span of more than nine orders of magnitude in energy, from 40 GHz microwaves to 200 keV gamma rays. Modern transition-edge sensors have noise-equivalent power as low as 10-20 W / Hz1/2 and energy resolution as good as 2 eV at 6 keV. These per-pixel sensitivities approach theoretical limits set by the underlying signals, motivating a rapid increase in pixel count to access new science. Compelling applications, like the non-destructive assay of nuclear material for treaty verification or the search for primordial gravity waves from inflation use arrays of these detectors to increase collection area or tile a focal plane. We developed three generations of SQUID multiplexers, optimizing the first for flux noise 0.17 muPhi0 / Hz1/2, the second for input current noise 19 pA / Hz1/2, and the last for practical multiplexing of large arrays of cosmic microwave background polarimeters based on transition-edge sensors. Using the last design we demonstrated multiplexed readout of prototype polarimeters with the performance required for the future development of a large-scale astronomical instrument.

On-chip integration of a superconducting microwave circulator and a Josephson parametric amplifier

NASA Astrophysics Data System (ADS)

Rosenthal, Eric I.; Chapman, Benjamin J.; Moores, Bradley A.; Kerckhoff, Joseph; Malnou, Maxime; Palken, D. A.; Mates, J. A. B.; Hilton, G. C.; Vale, L. R.; Ullom, J. N.; Lehnert, K. W.

Recent progress in microwave amplification based on parametric processes in superconducting circuits has revolutionized the measurement of feeble microwave signals. These devices, which operate near the quantum limit, are routinely used in ultralow temperature cryostats to: readout superconducting qubits, search for axionic dark matter, and characterize astrophysical sensors. However, these amplifiers often require ferrite circulators to separate incoming and outgoing traveling waves. For this reason, measurement efficiency and scalability are limited. In order to facilitate the routing of quantum signals we have created a superconducting, on-chip microwave circulator without permanent magnets. We integrate our circulator on-chip with a Josephson parametric amplifier for the purpose of near quantum-limited directional amplification. In this talk I will present a design overview and preliminary measurements.

Microwave amplification based on quasiparticle SIS up and down frequency converters

NASA Astrophysics Data System (ADS)

Kojima, T.; Uzawa, Y.; Shan, W.

2018-02-01

Heterodyne instruments have recently attained quantum-limited low-noise performance, particularly in radio astronomy, but it is difficult to develop large heterodyne arrays such as a modern radio camera using cryogenic sensitive detectors based on microwave kinetic inductance detectors, transition edge sensors, etc. In the realization of the heterodyne array, the reduction of power dissipation for semiconductor-based amplifiers remains a major challenge. Alternatively, superconducting parametric amplifiers still seem to have several barriers to application, especially in terms of operating temperature. Here, we show a novel concept of microwave amplification based on up and down frequency-conversion processes using quasiparticle superconductor-insulator-superconductor (SIS) tunnel junctions. We demonstrate positive gain using a proof-of-concept test module, which operates with a power dissipation of several μW at a bath temperature of 4 K. The performance of the module suggests great potential for application in large arrays.

Identification of nonclassical properties of light with multiplexing layouts

NASA Astrophysics Data System (ADS)

Sperling, J.; Eckstein, A.; Clements, W. R.; Moore, M.; Renema, J. J.; Kolthammer, W. S.; Nam, S. W.; Lita, A.; Gerrits, T.; Walmsley, I. A.; Agarwal, G. S.; Vogel, W.

2017-07-01

In Sperling et al. [Phys. Rev. Lett. 118, 163602 (2017), 10.1103/PhysRevLett.118.163602], we introduced and applied a detector-independent method to uncover nonclassicality. Here, we extend those techniques and give more details on the performed analysis. We derive a general theory of the positive-operator-valued measure that describes multiplexing layouts with arbitrary detectors. From the resulting quantum version of a multinomial statistics, we infer nonclassicality probes based on a matrix of normally ordered moments. We discuss these criteria and apply the theory to our data which are measured with superconducting transition-edge sensors. Our experiment produces heralded multiphoton states from a parametric down-conversion light source. We show that the known notions of sub-Poisson and sub-binomial light can be deduced from our general approach, and we establish the concept of sub-multinomial light, which is shown to outperform the former two concepts of nonclassicality for our data.

Identification of nonclassical properties of light with multiplexing layouts

PubMed Central

Sperling, J.; Eckstein, A.; Clements, W. R.; Moore, M.; Renema, J. J.; Kolthammer, W. S.; Nam, S. W.; Lita, A.; Gerrits, T.; Walmsley, I. A.; Agarwal, G. S.; Vogel, W.

2018-01-01

In Sperling et al. [Phys. Rev. Lett. 118, 163602 (2017)], we introduced and applied a detector-independent method to uncover nonclassicality. Here, we extend those techniques and give more details on the performed analysis. We derive a general theory of the positive-operator-valued measure that describes multiplexing layouts with arbitrary detectors. From the resulting quantum version of a multinomial statistics, we infer nonclassicality probes based on a matrix of normally ordered moments. We discuss these criteria and apply the theory to our data which are measured with superconducting transition-edge sensors. Our experiment produces heralded multiphoton states from a parametric down-conversion light source. We show that the known notions of sub-Poisson and sub-binomial light can be deduced from our general approach, and we establish the concept of sub-multinomial light, which is shown to outperform the former two concepts of nonclassicality for our data. PMID:29670949

Room-temperature-deposited dielectrics and superconductors for integrated photonics.

PubMed

Shainline, Jeffrey M; Buckley, Sonia M; Nader, Nima; Gentry, Cale M; Cossel, Kevin C; Cleary, Justin W; Popović, Miloš; Newbury, Nathan R; Nam, Sae Woo; Mirin, Richard P

2017-05-01

We present an approach to fabrication and packaging of integrated photonic devices that utilizes waveguide and detector layers deposited at near-ambient temperature. All lithography is performed with a 365 nm i-line stepper, facilitating low cost and high scalability. We have shown low-loss SiN waveguides, high-Q ring resonators, critically coupled ring resonators, 50/50 beam splitters, Mach-Zehnder interferometers (MZIs) and a process-agnostic fiber packaging scheme. We have further explored the utility of this process for applications in nonlinear optics and quantum photonics. We demonstrate spectral tailoring and octave-spanning supercontinuum generation as well as the integration of superconducting nanowire single photon detectors with MZIs and channel-dropping filters. The packaging approach is suitable for operation up to 160 ^°C as well as below 1 K. The process is well suited for augmentation of existing foundry capabilities or as a stand-alone process.

Signatures of Induced Superconductivity in NbTi Contacted InAs Quantum Wells

NASA Astrophysics Data System (ADS)

McFadden, Anthony; Shabani, Javad; Shojaei, Borzoyeh; Lee, Joon Sue; Palmstrøm, Chris

We have studied electrical transport through InAs quantum wells grown by MBE with unannealed superconducting NbTi contacts deposited ex-situ and patterned by optical photolithography. Characterization of the InAs 2DEG's without superconducting contacts yields typical mobilities greater than 100,000 cm2/Vs at a density of 4e11 cm-2. NbTi-InAs-NbTi (SNS) and NbTi-InAs (SN) devices with dimensions greater than 1 µm are fabricated using optical lithography. Although the dimensions of the fabricated SNS devices are too large to observe a supercurrent, signatures of superconductivity induced in the InAs are present. We observe two superconducting critical temperatures: one of the NbTi leads (Tc~8K), and a second (Tc <4.5K) attributed to superconductivity induced in the InAs channel. dI/dV vs V spectroscopy on SNS junctions below the second critical temperature shows a conductance maximum at zero applied voltage while conductance minima appear at finite bias voltage which is attributed to the presence of an induced superconducting gap in the InAs quantum well. This work has been supported by Microsoft research.

SNSPD with parallel nanowires (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ejrnaes, Mikkel; Parlato, Loredana; Gaggero, Alessandro; Mattioli, Francesco; Leoni, Roberto; Pepe, Giampiero; Cristiano, Roberto

2017-05-01

Superconducting nanowire single-photon detectors (SNSPDs) have shown to be promising in applications such as quantum communication and computation, quantum optics, imaging, metrology and sensing. They offer the advantages of a low dark count rate, high efficiency, a broadband response, a short time jitter, a high repetition rate, and no need for gated-mode operation. Several SNSPD designs have been proposed in literature. Here, we discuss the so-called parallel nanowires configurations. They were introduced with the aim of improving some SNSPD property like detection efficiency, speed, signal-to-noise ratio, or photon number resolution. Although apparently similar, the various parallel designs are not the same. There is no one design that can improve the mentioned properties all together. In fact, each design presents its own characteristics with specific advantages and drawbacks. In this work, we will discuss the various designs outlining peculiarities and possible improvements.

Discrete-time quantum walk with nitrogen-vacancy centers in diamond coupled to a superconducting flux qubit

NASA Astrophysics Data System (ADS)

Hardal, Ali Ü. C.; Xue, Peng; Shikano, Yutaka; Müstecaplıoğlu, Özgür E.; Sanders, Barry C.

2013-08-01

We propose a quantum-electrodynamics scheme for implementing the discrete-time, coined quantum walk with the walker corresponding to the phase degree of freedom for a quasimagnon field realized in an ensemble of nitrogen-vacancy centers in diamond. The coin is realized as a superconducting flux qubit. Our scheme improves on an existing proposal for implementing quantum walks in cavity quantum electrodynamics by removing the cumbersome requirement of varying drive-pulse durations according to mean quasiparticle number. Our improvement is relevant to all indirect-coin-flip cavity quantum-electrodynamics realizations of quantum walks. Our numerical analysis shows that this scheme can realize a discrete quantum walk under realistic conditions.

Cryogenic gamma detectors enable direct detection of 236U and minor actinides for non-destructive assay [Cryogenic gamma detectors enable direct detection of minor actinides for non-destructive assay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velazquez, Miguel; Dreyer, Jonathan; Drury, Owen B.

2015-09-05

Here, we demonstrate the utility of a superconducting transition edge sensor (TES) γ-ray detector with high energy resolution and low Compton background for non-destructive assay (NDA) of a uranium sample from reprocessed nuclear fuel. We show that TES γ-detectors can separate low energy actinide γ-emissions from the background and nearby lines, even from minor isotopes whose signals are often obscured in NDA with conventional Ge detectors. Superconducting γ detectors may therefore bridge the gap between high-accuracy destructive assay (DA) and easier to-use NDA.

Superconductivity bordering Rashba type topological transition

DOE PAGES

Jin, M. L.; Sun, F.; Xing, L. Y.; ...

2017-01-04

Strong spin orbital interaction (SOI) can induce unique quantum phenomena such as topological insulators, the Rashba effect, or p-wave superconductivity. Combining these three quantum phenomena into a single compound has important scientific implications. Here we report experimental observations of consecutive quantum phase transitions from a Rashba type topological trivial phase to topological insulator state then further proceeding to superconductivity in a SOI compound BiTeI tuned via pressures. The electrical resistivity measurement with V shape change signals the transition from a Rashba type topological trivial to a topological insulator phase at 2 GPa, which is caused by an energy gap closemore » then reopen with band inverse. Superconducting transition appears at 8 GPa with a critical temperature T C of 5.3 K. Structure refinements indicate that the consecutive phase transitions are correlated to the changes in the Bi–Te bond and bond angle as function of pressures. As a result, the Hall Effect measurements reveal an intimate relationship between superconductivity and the unusual change in carrier density that points to possible unconventional superconductivity.« less

Quantum-Circuit Refrigerator

NASA Astrophysics Data System (ADS)

MöTtöNen, Mikko; Tan, Kuan Y.; Masuda, Shumpei; Partanen, Matti; Lake, Russell E.; Govenius, Joonas; Silveri, Matti; Grabert, Hermann

Quantum technology holds great potential in providing revolutionizing practical applications. However, fast and precise cooling of the functional quantum degrees of freedom on demand remains a major challenge in many solid-state implementations, such as superconducting circuits. We demonstrate direct cooling of a superconducting resonator mode using voltage-controllable quantum tunneling of electrons in a nanoscale refrigerator. In our first experiments on this type of a quantum-circuit refrigerator, we measure the drop in the mode temperature by electron thermometry at a resistor which is coupled to the resonator mode through ohmic losses. To eliminate unwanted dissipation, we remove the probe resistor and directly observe the power spectrum of the resonator output in agreement with the so-called P(E) theory. We also demonstrate in microwave reflection experiments that the internal quality factor of the resonator can be tuned by orders of magnitude. In the future, our refrigerator can be integrated with different quantum electric devices, potentially enhancing their performance. For example, it may prove useful in the initialization of superconducting quantum bits and in dissipation-assisted quantum annealing. We acknowledge European Research Council Grant SINGLEOUT (278117) and QUESS (681311) for funding.

0 - π Quantum transition in a carbon nanotube Josephson junction: Universal phase dependence and orbital degeneracy

NASA Astrophysics Data System (ADS)

Delagrange, R.; Weil, R.; Kasumov, A.; Ferrier, M.; Bouchiat, H.; Deblock, R.

2018-05-01

In a quantum dot hybrid superconducting junction, the behavior of the supercurrent is dominated by Coulomb blockade physics, which determines the magnetic state of the dot. In particular, in a single level quantum dot singly occupied, the sign of the supercurrent can be reversed, giving rise to a π-junction. This 0 - π transition, corresponding to a singlet-doublet transition, is then driven by the gate voltage or by the superconducting phase in the case of strong competition between the superconducting proximity effect and Kondo correlations. In a two-level quantum dot, such as a clean carbon nanotube, 0- π transitions exist as well but, because more cotunneling processes are allowed, are not necessarily associated to a magnetic state transition of the dot. In this proceeding, after a review of 0- π transitions in Josephson junctions, we present measurements of current-phase relation in a clean carbon nanotube quantum dot, in the single and two-level regimes. In the single level regime, close to orbital degeneracy and in a regime of strong competition between local electronic correlations and superconducting proximity effect, we find that the phase diagram of the phase-dependent transition is a universal characteristic of a discontinuous level-crossing quantum transition at zero temperature. In the case where the two levels are involved, the nanotube Josephson current exhibits a continuous 0 - π transition, independent of the superconducting phase, revealing a different physical mechanism of the transition.

Nanoantenna enhancement for telecom-wavelength superconducting single photon detectors.

PubMed

Heath, Robert M; Tanner, Michael G; Drysdale, Timothy D; Miki, Shigehito; Giannini, Vincenzo; Maier, Stefan A; Hadfield, Robert H

2015-02-11

Superconducting nanowire single photon detectors are rapidly emerging as a key infrared photon-counting technology. Two front-side-coupled silver dipole nanoantennas, simulated to have resonances at 1480 and 1525 nm, were fabricated in a two-step process. An enhancement of 50 to 130% in the system detection efficiency was observed when illuminating the antennas. This offers a pathway to increasing absorption into superconducting nanowires, creating larger active areas, and achieving more efficient detection at longer wavelengths.

Experimental demonstration of conflicting interest nonlocal games using superconducting qubits

NASA Astrophysics Data System (ADS)

Situ, Haozhen; Li, Lvzhou; Huang, Zhiming; He, Zhimin; Zhang, Cai

2018-06-01

Conflicting interest nonlocal games are special Bayesian games played by noncooperative players without communication. In recent years, some conflicting interest nonlocal games have been proposed where quantum advice can help players to obtain higher payoffs. In this work we perform an experiment of six conflicting interest nonlocal games using the IBM quantum computer made up of five superconducting qubits. The experimental results demonstrate quantum advantage in four of these games, whereas the other two games fail to showcase quantum advantage in the experiment.

Analog cosmological particle generation in a superconducting circuit

NASA Astrophysics Data System (ADS)

Tian, Zehua; Jing, Jiliang; Dragan, Andrzej

2017-06-01

We propose the use of a waveguidelike transmission line based on direct-current superconducting quantum interference devices (dc-SQUID) and demonstrate that the node flux in this transmission line behaves in the same way as quantum fields in an expanding (or contracting) universe. We show how to detect the analog cosmological particle generation and analyze its feasibility with current circuit quantum electrodynamics (cQED) technology. Our setup in principle paves a new way for the exploration of analog quantum gravitational effects.

One-way quantum computing in superconducting circuits

NASA Astrophysics Data System (ADS)

Albarrán-Arriagada, F.; Alvarado Barrios, G.; Sanz, M.; Romero, G.; Lamata, L.; Retamal, J. C.; Solano, E.

2018-03-01

We propose a method for the implementation of one-way quantum computing in superconducting circuits. Measurement-based quantum computing is a universal quantum computation paradigm in which an initial cluster state provides the quantum resource, while the iteration of sequential measurements and local rotations encodes the quantum algorithm. Up to now, technical constraints have limited a scalable approach to this quantum computing alternative. The initial cluster state can be generated with available controlled-phase gates, while the quantum algorithm makes use of high-fidelity readout and coherent feedforward. With current technology, we estimate that quantum algorithms with above 20 qubits may be implemented in the path toward quantum supremacy. Moreover, we propose an alternative initial state with properties of maximal persistence and maximal connectedness, reducing the required resources of one-way quantum computing protocols.

Single-photon imager based on a superconducting nanowire delay line

NASA Astrophysics Data System (ADS)

Zhao, Qing-Yuan; Zhu, Di; Calandri, Niccolò; Dane, Andrew E.; McCaughan, Adam N.; Bellei, Francesco; Wang, Hao-Zhu; Santavicca, Daniel F.; Berggren, Karl K.

2017-03-01

Detecting spatial and temporal information of individual photons is critical to applications in spectroscopy, communication, biological imaging, astronomical observation and quantum-information processing. Here we demonstrate a scalable single-photon imager using a single continuous superconducting nanowire that is not only a single-photon detector but also functions as an efficient microwave delay line. In this context, photon-detection pulses are guided in the nanowire and enable the readout of the position and time of photon-absorption events from the arrival times of the detection pulses at the nanowire's two ends. Experimentally, we slowed down the velocity of pulse propagation to ∼2% of the speed of light in free space. In a 19.7 mm long nanowire that meandered across an area of 286 × 193 μm2, we were able to resolve ∼590 effective pixels with a temporal resolution of 50 ps (full width at half maximum). The nanowire imager presents a scalable approach for high-resolution photon imaging in space and time.

Universal quantum gate set approaching fault-tolerant thresholds with superconducting qubits.

PubMed

Chow, Jerry M; Gambetta, Jay M; Córcoles, A D; Merkel, Seth T; Smolin, John A; Rigetti, Chad; Poletto, S; Keefe, George A; Rothwell, Mary B; Rozen, J R; Ketchen, Mark B; Steffen, M

2012-08-10

We use quantum process tomography to characterize a full universal set of all-microwave gates on two superconducting single-frequency single-junction transmon qubits. All extracted gate fidelities, including those for Clifford group generators, single-qubit π/4 and π/8 rotations, and a two-qubit controlled-not, exceed 95% (98%), without (with) subtracting state preparation and measurement errors. Furthermore, we introduce a process map representation in the Pauli basis which is visually efficient and informative. This high-fidelity gate set serves as a critical building block towards scalable architectures of superconducting qubits for error correction schemes and pushes up on the known limits of quantum gate characterization.

Universal Quantum Gate Set Approaching Fault-Tolerant Thresholds with Superconducting Qubits

NASA Astrophysics Data System (ADS)

Chow, Jerry M.; Gambetta, Jay M.; Córcoles, A. D.; Merkel, Seth T.; Smolin, John A.; Rigetti, Chad; Poletto, S.; Keefe, George A.; Rothwell, Mary B.; Rozen, J. R.; Ketchen, Mark B.; Steffen, M.

2012-08-01

We use quantum process tomography to characterize a full universal set of all-microwave gates on two superconducting single-frequency single-junction transmon qubits. All extracted gate fidelities, including those for Clifford group generators, single-qubit π/4 and π/8 rotations, and a two-qubit controlled-not, exceed 95% (98%), without (with) subtracting state preparation and measurement errors. Furthermore, we introduce a process map representation in the Pauli basis which is visually efficient and informative. This high-fidelity gate set serves as a critical building block towards scalable architectures of superconducting qubits for error correction schemes and pushes up on the known limits of quantum gate characterization.

A graph-theoretical representation of multiphoton resonance processes in superconducting quantum circuits

DOE PAGES

Jooya, Hossein Z.; Reihani, Kamran; Chu, Shih-I

2016-11-21

We propose a graph-theoretical formalism to study generic circuit quantum electrodynamics systems consisting of a two level qubit coupled with a single-mode resonator in arbitrary coupling strength regimes beyond rotating-wave approximation. We define colored-weighted graphs, and introduce different products between them to investigate the dynamics of superconducting qubits in transverse, longitudinal, and bidirectional coupling schemes. In conclusion, the intuitive and predictive picture provided by this method, and the simplicity of the mathematical construction, are demonstrated with some numerical studies of the multiphoton resonance processes and quantum interference phenomena for the superconducting qubit systems driven by intense ac fields.

Bell-state generation on remote superconducting qubits with dark photons

NASA Astrophysics Data System (ADS)

Hua, Ming; Tao, Ming-Jie; Alsaedi, Ahmed; Hayat, Tasawar; Wei, Hai-Rui; Deng, Fu-Guo

2018-06-01

We present a scheme to generate the Bell state deterministically on remote transmon qubits coupled to different 1D superconducting resonators connected by a long superconducting transmission line. Using the coherent evolution of the entire system in the all-resonance regime, the transmission line need not to be populated with microwave photons which can robust against the long transmission line loss. This lets the scheme more applicable to the distributed quantum computing on superconducting quantum circuit. Besides, the influence from the small anharmonicity of the energy levels of the transmon qubits can be ignored safely.

Fate of superconductivity in three-dimensional disordered Luttinger semimetals

NASA Astrophysics Data System (ADS)

Mandal, Ipsita

2018-05-01

Superconducting instability can occur in three-dimensional quadratic band crossing semimetals only at a finite coupling strength due to the vanishing of density of states at the quadratic band touching point. Since realistic materials are always disordered to some extent, we study the effect of short-ranged-correlated disorder on this superconducting quantum critical point using a controlled loop-expansion applying dimensional regularization. The renormalization group (RG) scheme allows us to determine the RG flows of the various interaction strengths and shows that disorder destroys the superconducting quantum critical point. In fact, the system exhibits a runaway flow to strong disorder.

Complete Bell-state analysis for superconducting-quantum-interference-device qubits with a transitionless tracking algorithm

NASA Astrophysics Data System (ADS)

Kang, Yi-Hao; Chen, Ye-Hong; Shi, Zhi-Cheng; Huang, Bi-Hua; Song, Jie; Xia, Yan

2017-08-01

We propose a protocol for complete Bell-state analysis for two superconducting-quantum-interference-device qubits. The Bell-state analysis could be completed by using a sequence of microwave pulses designed by the transitionless tracking algorithm, which is a useful method in the technique of shortcut to adiabaticity. After the whole process, the information for distinguishing four Bell states will be encoded on two auxiliary qubits, while the Bell states remain unchanged. One can read out the information by detecting the auxiliary qubits. Thus the Bell-state analysis is nondestructive. The numerical simulations show that the protocol possesses a high success probability of distinguishing each Bell state with current experimental technology even when decoherence is taken into account. Thus, the protocol may have potential applications for the information readout in quantum communications and quantum computations in superconducting quantum networks.

Flux-tunable heat sink for quantum electric circuits.

PubMed

Partanen, M; Tan, K Y; Masuda, S; Govenius, J; Lake, R E; Jenei, M; Grönberg, L; Hassel, J; Simbierowicz, S; Vesterinen, V; Tuorila, J; Ala-Nissila, T; Möttönen, M

2018-04-20

Superconducting microwave circuits show great potential for practical quantum technological applications such as quantum information processing. However, fast and on-demand initialization of the quantum degrees of freedom in these devices remains a challenge. Here, we experimentally implement a tunable heat sink that is potentially suitable for the initialization of superconducting qubits. Our device consists of two coupled resonators. The first resonator has a high quality factor and a fixed frequency whereas the second resonator is designed to have a low quality factor and a tunable resonance frequency. We engineer the low quality factor using an on-chip resistor and the frequency tunability using a superconducting quantum interference device. When the two resonators are in resonance, the photons in the high-quality resonator can be efficiently dissipated. We show that the corresponding loaded quality factor can be tuned from above 10 5 down to a few thousand at 10 GHz in good quantitative agreement with our theoretical model.

Note: Increasing dynamic range of digital-to-analog converter using a superconducting quantum interference device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakanishi, Masakazu, E-mail: m.nakanishi@aist.go.jp

Responses of a superconducting quantum interference device (SQUID) are periodically dependent on magnetic flux coupling to its superconducting ring and the period is a flux quantum (Φ{sub o} = h/2e, where h and e, respectively, express Planck's constant and elementary charge). Using this periodicity, we had proposed a digital to analog converter using a SQUID (SQUID DAC) of first generation with linear current output, interval of which corresponded to Φ{sub o}. Modification for increasing dynamic range by interpolating within each interval is reported. Linearity of the interpolation was also based on the quantum periodicity. A SQUID DAC with dynamic rangemore » of about 1.4 × 10{sup 7} was created as a demonstration.« less

Scalable designs for quasiparticle-poisoning-protected topological quantum computation with Majorana zero modes

NASA Astrophysics Data System (ADS)

Karzig, Torsten; Knapp, Christina; Lutchyn, Roman M.; Bonderson, Parsa; Hastings, Matthew B.; Nayak, Chetan; Alicea, Jason; Flensberg, Karsten; Plugge, Stephan; Oreg, Yuval; Marcus, Charles M.; Freedman, Michael H.

2017-06-01

We present designs for scalable quantum computers composed of qubits encoded in aggregates of four or more Majorana zero modes, realized at the ends of topological superconducting wire segments that are assembled into superconducting islands with significant charging energy. Quantum information can be manipulated according to a measurement-only protocol, which is facilitated by tunable couplings between Majorana zero modes and nearby semiconductor quantum dots. Our proposed architecture designs have the following principal virtues: (1) the magnetic field can be aligned in the direction of all of the topological superconducting wires since they are all parallel; (2) topological T junctions are not used, obviating possible difficulties in their fabrication and utilization; (3) quasiparticle poisoning is abated by the charging energy; (4) Clifford operations are executed by a relatively standard measurement: detection of corrections to quantum dot energy, charge, or differential capacitance induced by quantum fluctuations; (5) it is compatible with strategies for producing good approximate magic states.

Enhancement of phonon backscattering due to confinement of ballistic phonon pathways in silicon as studied with a microfabricated phonon spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Otelaja, O. O.; Robinson, R. D., E-mail: rdr82@cornell.edu

2015-10-26

In this work, the mechanism for enhanced phonon backscattering in silicon is investigated. An understanding of phonon propagation through substrates has implications for engineering heat flow at the nanoscale, for understanding sources of decoherence in quantum systems, and for realizing efficient phonon-mediated particle detectors. In these systems, phonons that backscatter from the bottom of substrates, within the crystal or from interfaces, often contribute to the overall detector signal. We utilize a microscale phonon spectrometer, comprising superconducting tunnel junction emitters and detectors, to specifically probe phonon backscattering in silicon substrates (∼500 μm thick). By etching phonon “enhancers” or deep trenches (∼90 μm) aroundmore » the detectors, we show that the backscattered signal level increases by a factor of ∼2 for two enhancers versus one enhancer. Using a geometric analysis of the phonon pathways, we show that the mechanism of the backscattered phonon enhancement is due to confinement of the ballistic phonon pathways and increased scattering off the enhancer walls. Our result is applicable to the geometric design and patterning of substrates that are employed in phonon-mediated detection devices.« less

Building logical qubits in a superconducting quantum computing system

NASA Astrophysics Data System (ADS)

Gambetta, Jay M.; Chow, Jerry M.; Steffen, Matthias

2017-01-01

The technological world is in the midst of a quantum computing and quantum information revolution. Since Richard Feynman's famous `plenty of room at the bottom' lecture (Feynman, Engineering and Science23, 22 (1960)), hinting at the notion of novel devices employing quantum mechanics, the quantum information community has taken gigantic strides in understanding the potential applications of a quantum computer and laid the foundational requirements for building one. We believe that the next significant step will be to demonstrate a quantum memory, in which a system of interacting qubits stores an encoded logical qubit state longer than the incorporated parts. Here, we describe the important route towards a logical memory with superconducting qubits, employing a rotated version of the surface code. The current status of technology with regards to interconnected superconducting-qubit networks will be described and near-term areas of focus to improve devices will be identified. Overall, the progress in this exciting field has been astounding, but we are at an important turning point, where it will be critical to incorporate engineering solutions with quantum architectural considerations, laying the foundation towards scalable fault-tolerant quantum computers in the near future.

Quantum acoustics with superconducting qubits

NASA Astrophysics Data System (ADS)

Chu, Yiwen

2017-04-01

The ability to engineer and manipulate different types of quantum mechanical objects allows us to take advantage of their unique properties and create useful hybrid technologies. Thus far, complex quantum states and exquisite quantum control have been demonstrated in systems ranging from trapped ions to superconducting resonators. Recently, there have been many efforts to extend these demonstrations to the motion of complex, macroscopic objects. These mechanical objects have important applications as quantum memories or transducers for measuring and connecting different types of quantum systems. In particular, there have been a few experiments that couple motion to nonlinear quantum objects such as superconducting qubits. This opens up the possibility of creating, storing, and manipulating non-Gaussian quantum states in mechanical degrees of freedom. However, before sophisticated quantum control of mechanical motion can be achieved, we must realize systems with long coherence times while maintaining a sufficient interaction strength. These systems should be implemented in a simple and robust manner that allows for increasing complexity and scalability in the future. In this talk, I will describe our recent experiments demonstrating a high frequency bulk acoustic wave resonator that is strongly coupled to a superconducting qubit using piezoelectric transduction. In contrast to previous experiments with qubit-mechanical systems, our device requires only simple fabrication methods, extends coherence times to many microseconds, and provides controllable access to a multitude of phonon modes. We use this system to demonstrate basic quantum operations on the coupled qubit-phonon system. Straightforward improvements to the current device will allow for advanced protocols analogous to what has been shown in optical and microwave resonators, resulting in a novel resource for implementing hybrid quantum technologies.

Continuous measurement of two spatially separated superconducting qubits: quantum trajectories and statistics

NASA Astrophysics Data System (ADS)

Roch, Nicolas

2015-03-01

Measurement can be harnessed to probabilistically generate entanglement in the absence of local interactions, for example between spatially separated quantum objects. Continuous weak measurement allows us to observe the dynamics associated with this process. In particular, we perform joint dispersive readout of two superconducting transmon qubits separated by one meter of coaxial cable. We track the evolution of a joint quantum state under the influence of measurement, both as an ensemble and as a set of individual quantum trajectories. Analyzing the statistics of such quantum trajectories can shed new light on the underlying entangling mechanism.

Using Quasiparticle Poisoning To Detect Photons

NASA Technical Reports Server (NTRS)

Echternach, Pierre; Day, Peter

2006-01-01

According to a proposal, a phenomenon associated with excitation of quasiparticles in certain superconducting quantum devices would be exploited as a means of detecting photons with exquisite sensitivity. The phenomenon could also be exploited to perform medium-resolution spectroscopy. The proposal was inspired by the observation that Coulomb blockade devices upon which some quantum logic gates are based are extremely sensitive to quasiparticles excited above the superconducting gaps in their leads. The presence of quasiparticles in the leads can be easily detected via the charge states. If quasiparticles could be generated in the leads by absorption of photons, then the devices could be used as very sensitive detectors of electromagnetic radiation over the spectral range from x-rays to submillimeter waves. The devices in question are single-Cooper-pair boxes (SCBs), which are mesoscopic superconducting devices developed for quantum computing. An SCB consists of a small superconducting island connected to a reservoir via a small tunnel junction and connected to a voltage source through a gate capacitor. An SCB is an artificial two-level quantum system, the Hamiltonian of which can be controlled by the gate voltage. One measures the expected value of the charge of the eigenvectors of this quantum system by use of a radio-frequency single-electron transistor. A plot of this expected value of charge as a function of gate voltage resembles a staircase that, in the ideal case, consists of steps of height 2 e (where e is the charge of one electron). Experiments have shown that depending on the parameters of the device, quasiparticles in the form of "broken" Cooper pairs present in the reservoir can tunnel to the island, giving rise to steps of 1 e. This effect is sometimes called "poisoning." Simulations have shown that an extremely small average number of quasiparticles can generate a 1-e periodic signal. In a device according to the proposal, this poisoning would be turned to advantage. Depending on the wavelength, an antenna or other component would be used to couple radiation into the reservoir, wherein the absorption of photons would break Cooper pairs, thereby creating quasiparticles that, in turn, would tunnel to the island, creating a 1-e signal. On the basis of conservative estimates of device parameters derived from experimental data and computational simulations that fit the data, it has been estimated that the noise equivalent power of a device according to the proposal could be as low as 6 10(exp -22) W/Hz(exp 1/2). It has also been estimated that the spectroscopic resolution (photon energy divided by increment of photon energy) of such a device in visible light would exceed 100.

Development and evaluation of thin semi-rigid cables for superconducting detectors

NASA Astrophysics Data System (ADS)

Kasai, Soichi; Kushino, Akihiro

2015-03-01

We are developing semi-rigid cables for accurate readout of superconducting radiation/particle detectors and other low temperature experiments. The center conductor with a diameter of 0.86 mm is separated with seamless metal outer conductor by dielectric material, polytetrafluoroethylene. We used various metal materials with low thermal conductivity for the electrical conductors such as stainless-steel, cupro-nickel, brass, beryllium-copper, phosphor-bronze, niobium-titanium, and niobium. In addition to the conventional semi-rigid cables, low-pass-filter-type cables were manufactured and evaluated to cut the high frequency noise into superconducting detectors. We measured their low thermal conductance and attenuation property up to 10GHz below the liquid helium temperature.

Development of semi-rigid cables for low temperature superconducting detectors

NASA Astrophysics Data System (ADS)

Kushino, Akihiro; Kasai, Soichi

We are developing semi-rigid cables for accurate readout of superconducting radiation/particle detectors and other low temperature experiments. The center conductor with a diameter of 0.86 mm is separated with seamless metal outer conductor by dielectric material, polytetrafluoroethylene. We used various metal materials with low thermal conductivity for the electrical conductors such as stainless-steel, cupro-nickel, brass, beryllium-copper, phosphor-bronze, niobium-titanium, and niobium. In addition to the conventional semi-rigid cables, low-pass-filter type cables were manufactured and evaluated to cut the high frequency noise into superconducting detectors. We measured their low thermal conductance and attenuation property up to 10 GHz below the liquid helium temperature.

Low Loss Superconducting Microstrip Development at Argonne National Lab

DOE PAGES

Chang, C. L.; Ade, P. A. R.; Ahmed, Z.; ...

2014-11-20

Low loss superconducting microstrip is an essential component in realizing 100 kilo-pixel multichroic cosmic microwave background detector arrays. In this paper, we have been developing a low loss microstrip by understanding and controlling the loss mechanisms. We present the fabrication of the superconducting microstrip, the loss measurements at a few GHz frequencies using half-wavelength resonators, and the loss measurements at 220 GHz frequencies with the superconducting microstrip coupled to slot antennas at one end and to TES detectors at the other end. Finally, the measured loss tangent of the microstrip made of sputtered Nb and SiOx is 1-2e-3.

Superconducting quantum spin-Hall systems with giant orbital g-factors

NASA Astrophysics Data System (ADS)

Hankiewicz, Ewelina; Reinthaler, Rolf; Tkachov, Grigory

Topological aspects of superconductivity in quantum spin-Hall systems (QSHSs) such as thin layers of three-dimensional topological insulators (3D Tis) or two-dimensional Tis are in the focus of current research. Here, we describe a novel superconducting quantum spin-Hall effect (quantum spin Hall system in the proximity to the s-wave superconductor and in the orbital in-plane magnetic field), which is protected against elastic backscattering by combined time-reversal and particle-hole symmetry. This effect is characterized by spin-polarized edge states, which can be manipulated in weak magnetic fields due to a giant effective orbital g-factor, allowing the generation of spin currents. The phenomenon provides a novel solution to the outstanding challenge of detecting the spin-polarization of the edge states. Here we propose the detection of the edge polarization in the three-terminal junction using unusual transport properties of superconducting quantum Hall-effect: a non-monotonic excess current and a zero-bias conductance splitting. We thank for the financial support the German Science Foundation (DFG), Grants No HA 5893/4-1 within SPP 1666, HA5893/5-2 within FOR1162 and TK60/1-1 (G.T.), as well the ENB graduate school ``Topological insulators''.

Experimental Quantum Randomness Processing Using Superconducting Qubits

NASA Astrophysics Data System (ADS)

Yuan, Xiao; Liu, Ke; Xu, Yuan; Wang, Weiting; Ma, Yuwei; Zhang, Fang; Yan, Zhaopeng; Vijay, R.; Sun, Luyan; Ma, Xiongfeng

2016-07-01

Coherently manipulating multipartite quantum correlations leads to remarkable advantages in quantum information processing. A fundamental question is whether such quantum advantages persist only by exploiting multipartite correlations, such as entanglement. Recently, Dale, Jennings, and Rudolph negated the question by showing that a randomness processing, quantum Bernoulli factory, using quantum coherence, is strictly more powerful than the one with classical mechanics. In this Letter, focusing on the same scenario, we propose a theoretical protocol that is classically impossible but can be implemented solely using quantum coherence without entanglement. We demonstrate the protocol by exploiting the high-fidelity quantum state preparation and measurement with a superconducting qubit in the circuit quantum electrodynamics architecture and a nearly quantum-limited parametric amplifier. Our experiment shows the advantage of using quantum coherence of a single qubit for information processing even when multipartite correlation is not present.

Nanowire-based detector

DOEpatents

Berggren, Karl K; Hu, Xiaolong; Masciarelli, Daniele

2014-06-24

Systems, articles, and methods are provided related to nanowire-based detectors, which can be used for light detection in, for example, single-photon detectors. In one aspect, a variety of detectors are provided, for example one including an electrically superconductive nanowire or nanowires constructed and arranged to interact with photons to produce a detectable signal. In another aspect, fabrication methods are provided, including techniques to precisely reproduce patterns in subsequently formed layers of material using a relatively small number of fabrication steps. By precisely reproducing patterns in multiple material layers, one can form electrically insulating materials and electrically conductive materials in shapes such that incoming photons are redirected toward a nearby electrically superconductive materials (e.g., electrically superconductive nanowire(s)). For example, one or more resonance structures (e.g., comprising an electrically insulating material), which can trap electromagnetic radiation within its boundaries, can be positioned proximate the nanowire(s). The resonance structure can include, at its boundaries, electrically conductive material positioned proximate the electrically superconductive nanowire such that light that would otherwise be transmitted through the sensor is redirected toward the nanowire(s) and detected. In addition, electrically conductive material can be positioned proximate the electrically superconductive nanowire (e.g. at the aperture of the resonant structure), such that light is directed by scattering from this structure into the nanowire.

Realizing a Circuit Analog of an Optomechanical System with Longitudinally Coupled Superconducting Resonators

NASA Astrophysics Data System (ADS)

Eichler, C.; Petta, J. R.

2018-06-01

We realize a superconducting circuit analog of the generic cavity-optomechanical Hamiltonian by longitudinally coupling two superconducting resonators, which are an order of magnitude different in frequency. We achieve longitudinal coupling by embedding a superconducting quantum interference device into a high frequency resonator, making its resonance frequency depend on the zero point current fluctuations of a nearby low frequency L C resonator. By applying sideband drive fields we enhance the intrinsic coupling strength of about 15 kHz up to 280 kHz by controlling the amplitude of the drive field. Our results pave the way towards the exploration of optomechanical effects in a fully superconducting platform and could enable quantum optics experiments with photons in the yet unexplored radio frequency band.

Radiofrequency amplifier based on a dc superconducting quantum interference device

DOEpatents

Hilbert, Claude; Martinis, John M.; Clarke, John

1986-01-01

A low noise radiofrequency amplifier (10), using a dc SQUID (superconducting quantum interference device) as the input amplifying element. The dc SQUID (11) and an input coil (12) are maintained at superconductivity temperatures in a superconducting shield (13), with the input coil (12) inductively coupled to the superconducting ring (17) of the dc SQUID (11). A radiofrequency signal from outside the shield (13) is applied to the input coil (12), and an amplified radiofrequency signal is developed across the dc SQUID ring (17) and transmitted to exteriorly of the shield (13). A power gain of 19.5.+-.0.5 dB has been achieved with a noise temperature of 1.0.+-.0.4 K. at a frequency of 100 MHz.

Design and validation of a large-format transition edge sensor array magnetic shielding system for space application

NASA Astrophysics Data System (ADS)

Bergen, A.; van Weers, H. J.; Bruineman, C.; Dhallé, M. M. J.; Krooshoop, H. J. G.; ter Brake, H. J. M.; Ravensberg, K.; Jackson, B. D.; Wafelbakker, C. K.

2016-10-01

The paper describes the development and the experimental validation of a cryogenic magnetic shielding system for transition edge sensor based space detector arrays. The system consists of an outer mu-metal shield and an inner superconducting niobium shield. First, a basic comparison is made between thin-walled mu-metal and superconducting shields, giving an off-axis expression for the field inside a cup-shaped superconductor as a function of the transverse external field. Starting from these preliminary analytical considerations, the design of an adequate and realistic shielding configuration for future space flight applications (either X-IFU [D. Barret et al., e-print arXiv:1308.6784 [astro-ph.IM] (2013)] or SAFARI [B. Jackson et al., IEEE Trans. Terahertz Sci. Technol. 2, 12 (2012)]) is described in more detail. The numerical design and verification tools (static and dynamic finite element method (FEM) models) are discussed together with their required input, i.e., the magnetic-field dependent permeability data. Next, the actual manufacturing of the shields is described, including a method to create a superconducting joint between the two superconducting shield elements that avoid flux penetration through the seam. The final part of the paper presents the experimental verification of the model predictions and the validation of the shield's performance. The shields were cooled through the superconducting transition temperature of niobium in zero applied magnetic field (<10 nT) or in a DC field with magnitude ˜100 μT, applied either along the system's symmetry axis or perpendicular to it. After cool-down, DC trapped flux profiles were measured along the shield axis with a flux-gate magnetometer and the attenuation of externally applied AC fields (100 μT, 0.1 Hz, both axial and transverse) was verified along this axis with superconducting quantum interference device magnetometers. The system's measured on-axis shielding factor is greater than 106, well exceeding the requirement of the envisaged missions. Following field-cooling in an axial field of 85 μT, the residual internal DC field normal to the detector plane is less than 1 μT. The trapped field patterns are compared to the predictions of the dynamic FEM model, which describes them well in the region where the internal field exceeds 6 μT.

Design and validation of a large-format transition edge sensor array magnetic shielding system for space application.

PubMed

Bergen, A; van Weers, H J; Bruineman, C; Dhallé, M M J; Krooshoop, H J G; Ter Brake, H J M; Ravensberg, K; Jackson, B D; Wafelbakker, C K

2016-10-01

The paper describes the development and the experimental validation of a cryogenic magnetic shielding system for transition edge sensor based space detector arrays. The system consists of an outer mu-metal shield and an inner superconducting niobium shield. First, a basic comparison is made between thin-walled mu-metal and superconducting shields, giving an off-axis expression for the field inside a cup-shaped superconductor as a function of the transverse external field. Starting from these preliminary analytical considerations, the design of an adequate and realistic shielding configuration for future space flight applications (either X-IFU [D. Barret et al., e-print arXiv:1308.6784 [astro-ph.IM] (2013)] or SAFARI [B. Jackson et al., IEEE Trans. Terahertz Sci. Technol. 2, 12 (2012)]) is described in more detail. The numerical design and verification tools (static and dynamic finite element method (FEM) models) are discussed together with their required input, i.e., the magnetic-field dependent permeability data. Next, the actual manufacturing of the shields is described, including a method to create a superconducting joint between the two superconducting shield elements that avoid flux penetration through the seam. The final part of the paper presents the experimental verification of the model predictions and the validation of the shield's performance. The shields were cooled through the superconducting transition temperature of niobium in zero applied magnetic field (<10 nT) or in a DC field with magnitude ∼100 μT, applied either along the system's symmetry axis or perpendicular to it. After cool-down, DC trapped flux profiles were measured along the shield axis with a flux-gate magnetometer and the attenuation of externally applied AC fields (100 μT, 0.1 Hz, both axial and transverse) was verified along this axis with superconducting quantum interference device magnetometers. The system's measured on-axis shielding factor is greater than 10 6 , well exceeding the requirement of the envisaged missions. Following field-cooling in an axial field of 85 μT, the residual internal DC field normal to the detector plane is less than 1 μT. The trapped field patterns are compared to the predictions of the dynamic FEM model, which describes them well in the region where the internal field exceeds 6 μT.

Frequency-domain cascading microwave superconducting quantum interference device multiplexers; beyond limitations originating from room-temperature electronics

NASA Astrophysics Data System (ADS)

Kohjiro, Satoshi; Hirayama, Fuminori

2018-07-01

A novel approach, frequency-domain cascading microwave multiplexers (MW-Mux), has been proposed and its basic operation has been demonstrated to increase the number of pixels multiplexed in a readout line U of MW-Mux for superconducting detector arrays. This method is an alternative to the challenging development of wideband, large power, and spurious-free room-temperature (300 K) electronics. The readout system for U pixels consists of four main parts: (1) multiplexer chips connected in series those contain U superconducting resonators in total. (2) A cryogenic high-electron-mobility transistor amplifier (HEMT). (3) A 300 K microwave frequency comb generator based on N(≡U/M) parallel units of digital-to-analog converters (DAC). (4) N parallel units of 300 K analog-to-digital converters (ADC). Here, M is the number of tones each DAC produces and each ADC handles. The output signal of U detectors multiplexed at the cryogenic stage is transmitted through a cable to the room temperature and divided into N processors where each handles M pixels. Due to the reduction factor of 1/N, U is not anymore dominated by the 300 K electronics but can be increased up to the potential value determined by either the bandwidth or the spurious-free power of the HEMT. Based on experimental results on the prototype system with N = 2 and M = 3, neither excess inter-pixel crosstalk nor excess noise has been observed in comparison with conventional MW-Mux. This indicates that the frequency-domain cascading MW-Mux provides the full (100%) usage of the HEMT band by assigning N 300 K bands on the frequency axis without inter-band gaps.

Progress Towards High-Sensitivity Arrays of Detectors of Sub-mm Radiation using Superconducting Tunnel Junctions with Radio-Frequency Single-Electron Transistors

NASA Technical Reports Server (NTRS)

Stevenson, T. R.; Hsieh, W.-T.; Li, M. J.; Stahle, C. M.; Wollack, E. J.; Schoelkopf, R. J.; Krebs, Carolyn (Technical Monitor)

2002-01-01

The science drivers for the SPIRIT/SPECS missions demand sensitive, fast, compact, low-power, large-format detector arrays for high resolution imaging and spectroscopy in the far infrared and submillimeter. Detector arrays with 10,000 pixels and sensitivity less than 10(exp 20)-20 W/Hz(exp 20)0.5 are needed. Antenna-coupled superconducting tunnel junction detectors with integrated rf single-electron transistor readout amplifiers have the potential for achieving this high level of sensitivity, and can take advantage of an rf multiplexing technique when forming arrays. The device consists of an antenna structure to couple radiation into a small superconducting volume and cause quasiparticle excitations, and a single-electron transistor to measure currents through tunnel junction contacts to the absorber volume. We will describe optimization of device parameters, and recent results on fabrication techniques for producing devices with high yield for detector arrays. We will also present modeling of expected saturation power levels, antenna coupling, and rf multiplexing schemes.

Quantum criticality and nodal superconductivity in the FeAs-based superconductor KFe2As2.

PubMed

Dong, J K; Zhou, S Y; Guan, T Y; Zhang, H; Dai, Y F; Qiu, X; Wang, X F; He, Y; Chen, X H; Li, S Y

2010-02-26

The in-plane resistivity rho and thermal conductivity kappa of the FeAs-based superconductor KFe2As2 single crystal were measured down to 50 mK. We observe non-Fermi-liquid behavior rho(T) approximately T{1.5} at H{c{2}}=5 T, and the development of a Fermi liquid state with rho(T) approximately T{2} when further increasing the field. This suggests a field-induced quantum critical point, occurring at the superconducting upper critical field H{c{2}}. In zero field, there is a large residual linear term kappa{0}/T, and the field dependence of kappa_{0}/T mimics that in d-wave cuprate superconductors. This indicates that the superconducting gaps in KFe2As2 have nodes, likely d-wave symmetry. Such a nodal superconductivity is attributed to the antiferromagnetic spin fluctuations near the quantum critical point.

Innovative quantum technologies for microgravity fundamental physics and biological research

NASA Technical Reports Server (NTRS)

Kierk, I. K.

2002-01-01

This paper presents a new technology program, within the fundamental physics, focusing on four quantum technology areas: quantum atomics, quantum optics, space superconductivity and quantum sensor technology, and quantum field based sensor and modeling technology.

Quantum Optics with Superconducting Circuits: From Single Photons to Schrodinger Cats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schoelkopf, Rob

Over the last decade and a half, superconducting circuits have advanced to the point where we can generate and detect highly-entangled states, and perform universal quantum gates. Meanwhile, the coherence properties of these systems have improved more than 10,000-fold. I will describe recent experiments, such as the latest advance in coherence using a three-dimensional implementation of qubits interacting with microwave cavities, called “3D circuit QED.” The control and strong interactions possible in superconducting circuits make it possible to generate non-classical states of light, including large superpositions known as “Schrodinger cat” states. This field has many interesting prospects both for applicationsmore » in quantum information processing, and fundamental investigations of the boundary between the macroscopic classical world and the microscopic world of the quantum.« less

Superconducting Qubits as Mechanical Quantum Engines

NASA Astrophysics Data System (ADS)

Sachtleben, Kewin; Mazon, Kahio T.; Rego, Luis G. C.

2017-09-01

We propose the equivalence of superconducting qubits with a pistonlike mechanical quantum engine. The work reports a study on the nature of the nonequilibrium work exchanged with the quantum-nonadiabatic working medium, which is modeled as a multilevel coupled quantum well system subject to an external control parameter. The quantum dynamics is solved for arbitrary control protocols. It is shown that the work output has two components: one that depends instantaneously on the level populations and another that is due to the quantum coherences built in the system. The nonadiabatic coherent dynamics of the quantum engine gives rise to a resistance (friction) force that decreases the work output. We consider the functional equivalence of such a device and a rf-SQUID flux qubit.

Characterization and Modeling of Superconducting Josephson Junction Arrays at Low Voltage and Liquid Helium Temperatures

DTIC Science & Technology

2016-09-01

to the characteristics and extract the non-ideality. These capabilities and calibration results will assist in the characterization of advanced...superconductor-ionic quantum memory and computation devices. iv CONTENTS EXECUTIVE SUMMARY...Josephson effect makes these measurements useful for characterization and calibration of superconducting quantum memory and computational devices

Strong Coupling Superconductivity in the Vicinity of the Structural Quantum Critical Point in (CaxSr1-x)3Rh4Sn13

NASA Astrophysics Data System (ADS)

Yu, Wing Chi; Cheung, Yiu Wing; Saines, Paul J.; Imai, Masaki; Matsumoto, Takuya; Michioka, Chishiro; Yoshimura, Kazuyoshi; Goh, Swee K.

The family of the superconducting quasiskutterudites (CaxSr1-x)3Rh4Sn13 features a structural quantum critical point at xc = 0 . 9 , around which a dome-shaped variation of the superconducting transition temperature Tc is found. In this talk, we present the specific heat data for the normal and the superconducting states of the entire series straddling the quantum critical point. Our analysis indicates a significant lowering of the effective Debye temperature on approaching xc, which we interpret as a result of phonon softening accompanying the structural instability. Furthermore, a remarkably large enhancement of 2 Δ /kBTc and ΔC / γTc beyond the Bardeen-Cooper-Schrieffer values is found in the vicinity of the structural quantum critical point. Reference: Wing Chi Yu et al. Phys. Rev. Lett. (in press, 2015) This work was supported by the CUHK (Startup Grant, Direct Grant No. 4053071), UGC Hong Kong (ECS/24300214), Grants-in-Aid from MEXT (22350029 and 23550152), and Glasstone Bequest, Oxford.

Superconductivity versus quantum criticality: Effects of thermal fluctuations

NASA Astrophysics Data System (ADS)

Wang, Huajia; Wang, Yuxuan; Torroba, Gonzalo

2018-02-01

We study the interplay between superconductivity and non-Fermi liquid behavior of a Fermi surface coupled to a massless SU(N ) matrix boson near the quantum critical point. The presence of thermal infrared singularities in both the fermionic self-energy and the gap equation invalidates the Eliashberg approximation, and makes the quantum-critical pairing problem qualitatively different from that at zero temperature. Taking the large N limit, we solve the gap equation beyond the Eliashberg approximation, and obtain the superconducting temperature Tc as a function of N . Our results show an anomalous scaling between the zero-temperature gap and Tc. For N greater than a critical value, we find that Tc vanishes with a Berezinskii-Kosterlitz-Thouless scaling behavior, and the system retains non-Fermi liquid behavior down to zero temperature. This confirms and extends previous renormalization-group analyses done at T =0 , and provides a controlled example of a naked quantum critical point. We discuss the crucial role of thermal fluctuations in relating our results with earlier work where superconductivity always develops due to the special role of the first Matsubara frequency.

The upside of noise: engineered dissipation as a resource in superconducting circuits

NASA Astrophysics Data System (ADS)

Kapit, Eliot

2017-09-01

Historically, noise in superconducting circuits has been considered an obstacle to be removed. A large fraction of the research effort in designing superconducting circuits has focused on noise reduction, with great success, as coherence times have increased by four orders of magnitude in the past two decades. However, noise and dissipation can never be fully eliminated, and further, a rapidly growing body of theoretical and experimental work has shown that carefully tuned noise, in the form of engineered dissipation, can be a profoundly useful tool in designing and operating quantum circuits. In this article, I review important applications of engineered dissipation, including state generation, state stabilization, and autonomous quantum error correction, where engineered dissipation can mitigate the effect of intrinsic noise, reducing logical error rates in quantum information processing. Further, I provide a pedagogical review of the basic noise processes in superconducting qubits (photon loss and phase noise), and argue that any dissipative mechanism which can correct photon loss errors is very likely to automatically suppress dephasing. I also discuss applications for quantum simulation, and possible future research directions.

Coherent optical excitations in superconducting qubit chain

NASA Astrophysics Data System (ADS)

Ian, Hou; Liu, Yu-Xi

2012-06-01

In the recent years, the theories of quantum optics have been borrowed to study the flows of electron pairs and their interactions with the circuit photon in the superconducting qubit circuits. These studies bring about new theories of quantum optics, such as the tunable electromagnetically induced transparency effect, peculiar to the Cooper pairs in circuits. In this talk, we focus on a special type of superconducting qubit circuits: superconducting qubit chain (SQC), which comprises dozens of qubits linearly placed along a stripline resonator. Since the dimensions of the qubits and the stripline have made their interactions inhomogeneous, the SQC cannot be diagonalized using the usual Dicke model. We present a new theoretical method, the deformation-projection method, for the exact diagonalization of the collective excitations of the qubits. This method allows us to predict that these excitations emulate the behaviors of Wannier and Frenckel excitons in the solid-state systems. The spontaneous emissions from the individual qubits in SQC are relayed to their neighbors, eventually arriving at a coherent emission, known as superradiance. We present a quantum relay model, which is crucial to quantum information processing, based on this finding.

Detection of bacteria in suspension using a superconducting Quantum interference device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grossman, H.L.; Myers, W.R.; Vreeland, V.J.

2003-06-09

We demonstrate a technique for detecting magnetically-labeled Listeria monocytogenes and for measuring the binding rate between antibody-linked magnetic particles and bacteria. This assay, which is both sensitive and straightforward to perform, can quantify specific bacteria in a sample without the need to immobilize the bacteria or wash away unbound magnetic particles. In the measurement, we add 50 nm diameter superparamagnetic particles, coated with antibodies, to a liquid sample containing L. monocytogenes. We apply a pulsed magnetic field to align the magnetic dipole moments and use a high transition temperature Superconducting Quantum Interference Device (SQUID), an extremely sensitive detector of magneticmore » flux, to measure the magnetic relaxation signal when the field is turned off. Unbound particles randomize direction by Brownian rotation too quickly to be detected. In contrast, particles bound to L. monocytogenes are effectively immobilized and relax in about 1 s by rotation of the internal dipole moment. This Neel relaxation process is detected by the SQUID. The measurements indicate a detection limit of (5.6 {+-} 1.1) x 10{sup 6} L. monocytogenes for a 20 {micro}L sample volume. If the sample volume were reduced to 1 nL, we estimate that the detection limit could be improved to 230 {+-} 40 L. monocytogenes cells. Time-resolved measurements yield the binding rate between the particles and bacteria.« less

NanoSQUIDs: Basics & recent advances

NASA Astrophysics Data System (ADS)

José Martínez-Pérez, Maria; Koelle, Dieter

2017-08-01

Superconducting Quantum Interference Devices (SQUIDs) are one of the most popular devices in superconducting electronics. They combine the Josephson effect with the quantization of magnetic flux in superconductors. This gives rise to one of the most beautiful manifestations of macroscopic quantum coherence in the solid state. In addition, SQUIDs are extremely sensitive sensors allowing us to transduce magnetic flux into measurable electric signals. As a consequence, any physical observable that can be converted into magnetic flux, e.g., current, magnetization, magnetic field or position, becomes easily accessible to SQUID sensors. In the late 1980s it became clear that downsizing the dimensions of SQUIDs to the nanometric scale would encompass an enormous increase of their sensitivity to localized tiny magnetic signals. Indeed, nanoSQUIDs opened the way to the investigation of, e.g., individual magnetic nanoparticles or surface magnetic states with unprecedented sensitivities. The purpose of this chapter is to present a detailed survey of microscopic and nanoscopic SQUID sensors. We will start by discussing the principle of operation of SQUIDs, placing the emphasis on their application as ultrasensitive detectors for small localized magnetic signals. We will continue by reviewing a number of existing devices based on different kinds of Josephson junctions and materials, focusing on their advantages and drawbacks. The last sections are left for applications of nanoSQUIDs in the fields of scanning SQUID microscopy and magnetic particle characterization, placing special stress on the investigation of individual magnetic nanoparticles.

Innovative quantum technologies for microgravity fundamental physics and biological research

NASA Technical Reports Server (NTRS)

Kierk, I.; Israelsson, U.; Lee, M.

2001-01-01

This paper presents a new technology program, within the fundamental physics research program, focusing on four quantum technology areas: quantum atomics, quantum optics, space superconductivity and quantum sensor technology, and quantum fluid based sensor and modeling technology.

A Blueprint for Demonstrating Quantum Supremacy with Superconducting Qubits

NASA Technical Reports Server (NTRS)

Kechedzhi, Kostyantyn

2018-01-01

Long coherence times and high fidelity control recently achieved in scalable superconducting circuits paved the way for the growing number of experimental studies of many-qubit quantum coherent phenomena in these devices. Albeit full implementation of quantum error correction and fault tolerant quantum computation remains a challenge the near term pre-error correction devices could allow new fundamental experiments despite inevitable accumulation of errors. One such open question foundational for quantum computing is achieving the so called quantum supremacy, an experimental demonstration of a computational task that takes polynomial time on the quantum computer whereas the best classical algorithm would require exponential time and/or resources. It is possible to formulate such a task for a quantum computer consisting of less than a 100 qubits. The computational task we consider is to provide approximate samples from a non-trivial quantum distribution. This is a generalization for the case of superconducting circuits of ideas behind boson sampling protocol for quantum optics introduced by Arkhipov and Aaronson. In this presentation we discuss a proof-of-principle demonstration of such a sampling task on a 9-qubit chain of superconducting gmon qubits developed by Google. We discuss theoretical analysis of the driven evolution of the device resulting in output approximating samples from a uniform distribution in the Hilbert space, a quantum chaotic state. We analyze quantum chaotic characteristics of the output of the circuit and the time required to generate a sufficiently complex quantum distribution. We demonstrate that the classical simulation of the sampling output requires exponential resources by connecting the task of calculating the output amplitudes to the sign problem of the Quantum Monte Carlo method. We also discuss the detailed theoretical modeling required to achieve high fidelity control and calibration of the multi-qubit unitary evolution in the device. We use a novel cross-entropy statistical metric as a figure of merit to verify the output and calibrate the device controls. Finally, we demonstrate the statistics of the wave function amplitudes generated on the 9-gmon chain and verify the quantum chaotic nature of the generated quantum distribution. This verifies the implementation of the quantum supremacy protocol.

Analogue Hawking radiation in a dc-SQUID array transmission line.

PubMed

Nation, P D; Blencowe, M P; Rimberg, A J; Buks, E

2009-08-21

We propose the use of a superconducting transmission line formed from an array of direct-current superconducting quantum interference devices for investigating analogue Hawking radiation. Biasing the array with a space-time varying flux modifies the propagation velocity of the transmission line, leading to an effective metric with a horizon. Being a fundamentally quantum mechanical device, this setup allows for investigations of quantum effects such as backreaction and analogue space-time fluctuations on the Hawking process.

Non-resonant interactions between superconducting circuits coupled through a dc-SQUID

NASA Astrophysics Data System (ADS)

Jin, X. Y.; Lecocq, F.; Cicak, K.; Kotler, S. S.; Peterson, G. A.; Teufel, J. D.; Aumentado, J.; Simmonds, R. W.

We use a flux-biased direct current superconducting quantum interference device (dc-SQUID) to generate non-resonant tunable interactions between transmon qubits and resonators modes. By modulating the flux to the dc-SQUID, we can create an interaction with variable coupling rates from zero to greater than 100 MHz. We explore this system experimentally and describe its operation. Parametric coupling is important for constructing larger coupled systems, useful for both quantum information architectures and quantum simulators.

Noninvasive Quantum Measurement of Arbitrary Operator Order by Engineered Non-Markovian Detectors

NASA Astrophysics Data System (ADS)

Bülte, Johannes; Bednorz, Adam; Bruder, Christoph; Belzig, Wolfgang

2018-04-01

The development of solid-state quantum technologies requires the understanding of quantum measurements in interacting, nonisolated quantum systems. In general, a permanent coupling of detectors to a quantum system leads to memory effects that have to be taken into account in interpreting the measurement results. We analyze a generic setup of two detectors coupled to a quantum system and derive a compact formula in the weak-measurement limit that interpolates between an instantaneous (text-book type) and almost continuous—detector dynamics-dependent—measurement. A quantum memory effect that we term "system-mediated detector-detector interaction" is crucial to observe noncommuting observables simultaneously. Finally, we propose a mesoscopic double-dot detector setup in which the memory effect is tunable and that can be used to explore the transition to non-Markovian quantum measurements experimentally.

Spin-spin relaxation of protons in ferrofluids characterized with a high-Tc superconducting quantum interference device-detected magnetometer in microtesla fields

NASA Astrophysics Data System (ADS)

Liao, Shu-Hsien; Liu, Chieh-Wen; Yang, Hong-Chang; Chen, Hsin-Hsien; Chen, Ming-Jye; Chen, Kuen-Lin; Horng, Herng-Er; Wang, Li-Min; Yang, Shieh-Yueh

2012-06-01

In this work, the spin-spin relaxation of protons in ferrofluids is characterized using a high-Tc SQUID-based detector in microtesla fields. We found that spin-spin relaxation rate is enhanced in the presence of superparamagnetic nanoparticles. The enhanced relaxation rates are attributed to the microscopic field gradients from magnetic nanoparticles that dephase protons' spins nearby. The relaxation rates decrease when temperatures increase. Additionally, the alternating current magnetic susceptibility was inversely proportional to temperature. Those characteristics explained the enhanced Brownian motion of nanoparticles at high temperatures. Characterizing the relaxation will be helpful for assaying bio-molecules and magnetic resonance imaging in microtesla fields.

Identification of microorganisms using superconducting tunnel junctions and time-of-flight mass spectrometry

NASA Astrophysics Data System (ADS)

Ullom, J. N.; Frank, M.; Horn, J. M.; Labov, S. E.; Langry, K.; Benner, W. H.

2000-04-01

We present time-of-flight measurements of biological material ejected from bacterial spores following laser irradiation. Ion impacts are registered on a microchannel plate detector and on a Superconducting Tunnel Junction (STJ) detector. We compare mass spectra obtained with the two detectors. The STJ has better sensitivity to massive ions and also measures the energy of each ion. We show evidence that spores of different bacillus species produce distinctive mass spectra and associate the observed mass peaks with coat proteins.

Realizing a Circuit Analog of an Optomechanical System with Longitudinally Coupled Superconducting Resonators.

PubMed

Eichler, C; Petta, J R

2018-06-01

We realize a superconducting circuit analog of the generic cavity-optomechanical Hamiltonian by longitudinally coupling two superconducting resonators, which are an order of magnitude different in frequency. We achieve longitudinal coupling by embedding a superconducting quantum interference device into a high frequency resonator, making its resonance frequency depend on the zero point current fluctuations of a nearby low frequency LC resonator. By applying sideband drive fields we enhance the intrinsic coupling strength of about 15 kHz up to 280 kHz by controlling the amplitude of the drive field. Our results pave the way towards the exploration of optomechanical effects in a fully superconducting platform and could enable quantum optics experiments with photons in the yet unexplored radio frequency band.

Suppression of 1/f Flux Noise in Superconducting Quantum Circuits

NASA Astrophysics Data System (ADS)

Kumar, Pradeep; Freeland, John; Yu, Clare; Wu, Ruqian; Wang, Zhe; Wang, Hui; Shi, Chuntai; Pappas, David; McDermott, Robert

Low frequency 1/f magnetic flux noise is a dominant contributor to dephasing in superconducting quantum circuits. It is believed that the noise is due to a high density of unpaired magnetic defect states at the surface of the superconducting thin films. We have performed X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) experiments that point to adsorbed molecular oxygen as the dominant source of magnetism in these films. By improving the vacuum environment of our superconducting devices, we have achieved a significant reduction in surface magnetic susceptibility and 1/f flux noise power spectral density. These results open the door to realization of superconducting qubits with improved dephasing times. State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China.

Proximity coupling in superconductor-graphene heterostructures.

PubMed

Lee, Gil-Ho; Lee, Hu-Jong

2018-05-01

This review discusses the electronic properties and the prospective research directions of superconductor-graphene heterostructures. The basic electronic properties of graphene are introduced to highlight the unique possibility of combining two seemingly unrelated physics, superconductivity and relativity. We then focus on graphene-based Josephson junctions, one of the most versatile superconducting quantum devices. The various theoretical methods that have been developed to describe graphene Josephson junctions are examined, together with their advantages and limitations, followed by a discussion on the advances in device fabrication and the relevant length scales. The phase-sensitive properties and phase-particle dynamics of graphene Josephson junctions are examined to provide an understanding of the underlying mechanisms of Josephson coupling via graphene. Thereafter, microscopic transport of correlated quasiparticles produced by Andreev reflections at superconducting interfaces and their phase-coherent behaviors are discussed. Quantum phase transitions studied with graphene as an electrostatically tunable 2D platform are reviewed. The interplay between proximity-induced superconductivity and the quantum-Hall phase is discussed as a possible route to study topological superconductivity and non-Abelian physics. Finally, a brief summary on the prospective future research directions is given.

Proximity coupling in superconductor-graphene heterostructures

NASA Astrophysics Data System (ADS)

Lee, Gil-Ho; Lee, Hu-Jong

2018-05-01

This review discusses the electronic properties and the prospective research directions of superconductor-graphene heterostructures. The basic electronic properties of graphene are introduced to highlight the unique possibility of combining two seemingly unrelated physics, superconductivity and relativity. We then focus on graphene-based Josephson junctions, one of the most versatile superconducting quantum devices. The various theoretical methods that have been developed to describe graphene Josephson junctions are examined, together with their advantages and limitations, followed by a discussion on the advances in device fabrication and the relevant length scales. The phase-sensitive properties and phase-particle dynamics of graphene Josephson junctions are examined to provide an understanding of the underlying mechanisms of Josephson coupling via graphene. Thereafter, microscopic transport of correlated quasiparticles produced by Andreev reflections at superconducting interfaces and their phase-coherent behaviors are discussed. Quantum phase transitions studied with graphene as an electrostatically tunable 2D platform are reviewed. The interplay between proximity-induced superconductivity and the quantum-Hall phase is discussed as a possible route to study topological superconductivity and non-Abelian physics. Finally, a brief summary on the prospective future research directions is given.

Hardware-efficient Bell state preparation using Quantum Zeno Dynamics in superconducting circuits

NASA Astrophysics Data System (ADS)

Flurin, Emmanuel; Blok, Machiel; Hacohen-Gourgy, Shay; Martin, Leigh S.; Livingston, William P.; Dove, Allison; Siddiqi, Irfan

By preforming a continuous joint measurement on a two qubit system, we restrict the qubit evolution to a chosen subspace of the total Hilbert space. This extension of the quantum Zeno effect, called Quantum Zeno Dynamics, has already been explored in various physical systems such as superconducting cavities, single rydberg atoms, atomic ensembles and Bose Einstein condensates. In this experiment, two superconducting qubits are strongly dispersively coupled to a high-Q cavity (χ >> κ) allowing for the doubly excited state | 11 〉 to be selectively monitored. The Quantum Zeno Dynamics in the complementary subspace enables us to coherently prepare a Bell state. As opposed to dissipation engineering schemes, we emphasize that our protocol is deterministic, does not rely direct coupling between qubits and functions only using single qubit controls and cavity readout. Such Quantum Zeno Dynamics can be generalized to larger Hilbert space enabling deterministic generation of many-body entangled states, and thus realizes a decoherence-free subspace allowing alternative noise-protection schemes.

Algorithmes et architectures pour ordinateurs quantiques supraconducteurs

NASA Astrophysics Data System (ADS)

Blais, A.

2003-09-01

Algorithms and architectures for superconducting quantum computers Since its formulation, information theory was based, implicitly, on the laws of classical physics. Such a formulation is however incomplete because it does not take into account quantum reality. During the last twenty years, expansion of theory information to include quantum effects has known growing interest. The practical realization of a system for quantum data processing system, a quantum computer, presents however many challenges. In this book, we are interested in various aspects of these challenges. We start by presenting algorithmic concepts like optimization of quantum computations and geometric quantum computation. We then consider various designs and aspects of qubits based on Josephson junctions. In particular, an original approach to the interaction between superconducting qubits is presented. This approach is very general since it can be applied to various designs of qubits. Finally, we are interested in read-out of the superconductic flux qubits. The detector suggested here has the advantage that it is possible to uncouple it from the qubit when no measurement is in progress. Depuis sa formulation, la théorie de l'information a été basée, implicitement, sur les lois de la physique classique. Une telle formulation est toutefois incomplète puisqu'elle ne tient pas compte de la réalité quantique. Au cours des vingt dernières années, l'expansion de la théorie de l'information, de façon à englober les effets purement quantiques, a connu un intérêt grandissant. La réalisation d'un système de traitement de l'information quantique, un ordinateur quantique, présente toutefois de nombreux défis. Dans cet ouvrage, on s'intéresse à différents aspects concernant ces défis. On commence par présenter des concepts algorithmiques comme l'optimisation de calculs quantiques et le calcul quantique géométrique. Par la suite, on s'intéresse à différents designs et aspects de l'utilisation de qubits basés sur les jonctions Josephson. On présente entre autres une approche originale pour l'interaction entre qubits. Cette approche est très générale puisqu'elle peut être appliquée à différents designs de qubits. Finalement, on s'intéresse à la lecture des qubits supraconducteurs de flux. Le détecteur suggéré ici a l'avantage de pouvoir être découplé du qubit lorsqu'il n'y a pas de mesure en cours.

Multiband nodeless superconductivity near the charge-density-wave quantum critical point in ZrTe 3–xSe x

DOE PAGES

Cui, Shan; He, Lan -Po; Hong, Xiao -Chen; ...

2016-06-09

It was found that selenium doping can suppress the charge-density-wave (CDW) order and induce bulk superconductivity in ZrTe 3. The observed superconducting dome suggests the existence of a CDW quantum critical point (QCP) in ZrTe 3–x Se x near x ≈ 0.04. To elucidate the superconducting state near the CDW QCP, we measure the thermal conductivity of two ZrTe 3–x Se x single crystals (x = 0.044 and 0.051) down to 80 mK. For both samples, the residual linear term κ 0/T at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependencemore » of κ 0/T manifests a multigap behavior. Lastly, these results demonstrate multiple nodeless superconducting gaps in ZrTe 3–x Se x, which indicates conventional superconductivity despite of the existence of a CDW QCP.« less

Low-Loss, Low-Noise, Crystalline and Amorphous Silicon Dielectrics for Superconducting Microstriplines and Kinetic Inductance Detector Capacitors

NASA Astrophysics Data System (ADS)

Golwala, Sunil

Prospective future PCOS (Inflation Probe) and COR (Origins Space Telescope, FIR Interferometer) missions require large arrays of highly sensitive millimeter-wave and submillimeter (mm/submm) detectors, including spectroscopic detectors. A number of technology developments in superconducting sensors for these applications require lowloss dielectric thin films. Examples include: Microstrip-coupled superconducting mm/submm detectors, which rely on superconductor-dielectric-superconductor microstrip transmission line to transmit optical power from a coherent reception element (feed horn, lens coupled antenna, phased-array antenna) to detectors; Superconducting spectrometers (SuperSpec, TIME, MicroSpec), which use such microstrip to route optical power to detectors and to define spectral channels; Kinetic inductance detectors (KIDs), which use capacitors. In the above, the dielectric loss, quantified by the loss tangent (tan delta), is critical: it determines the optical loss in the microstrip, the resolution of spectral channels, and the two-level-system (TLS) dielectric fluctuation noise of the KID capacitor. Currently, the amorphous dielectrics SiO2 and SiNx are used because they are most convenient for fabrication. They have tan delta 1e-3. This loss tangent is acceptable for microstripline but severely limits the possible architectures and spectral resolving power, and it is too large for KID capacitors. Lower loss dielectric would result in a quantum leap in capability, opening up design space heretofore inaccessible and enabling design innovations. Specific impacts on the above technologies would be: For phased-array antennas, lower optical loss would allow the detectors to be moved away from the antenna, allowing them to be shielded from absorption of light that has not been spatially or spectrally filtered and also obviating long wiring busses. More sophisticated antenna designs, such as multiscale antennas covering a decade of spectral bandwidth, could be entertained; For superconducting spectrometers, lower loss would improve the spectral resolution limit, Rmax = (1/tan delta), from 1e3 to 2e5, sufficient for resolved extragalactic mm/submm spectroscopy, where intrinsic line widths are dnu/nu 1e-4 to 1e-3; For KIDs, the interdigitated capacitors (IDC) currently used could be replaced by parallel-plate capacitors 40 times smaller in area, presenting a number of advantages over IDCs in properties such as focal plane fill factor and mounting architecture, direct absorption, and inter-KID coupling. There exist two paths in the literature to lower loss: hydrogenated amorphous silicon (aSi:H) and crystalline silicon (cSi). Crystalline silicon intrinsically has tan delta < 5e-6, 200 times lower than SiO2 and SiNx. a-Si:H has been demonstrated with tan delta < 5e5, not as good as cSi but still 20 times better than SiO2 and SiNx. We will pursue the development of both options due their complementary advantages and challenges. While a process has already been demonstrated for 5 um cSi with delta < 1e-4 and consistent with other design/fabrication constraints, it has not been shown yet that this can be extended to more convenient 1 um and 2 um thicknesses. a-Si:H has been demonstrated to have tan delta < 1e-4, but the fabrication recipe is almost certainly machine-specific and may not be compatible with focal plane array fabrication due to adhesion or stress issues. Given the uncertainties and different constraints imposed by the two processes, it is sensible to pursue both. This development would contribute to filling the Critical Technology Gaps identified in the 2016 PCOS and COR Program Annual Technology Reports, specifically the PCOS “Advanced millimeter-wave focal plane arrays for CMB polarimetry” gap and the COR “Large-format, low-noise far-infrared and ultralow noise (FIR) direct detectors” and “Compact, Integrated Spectrometers for 100 to 1000 um” gaps.

Demonstration of a quantum error detection code using a square lattice of four superconducting qubits

PubMed Central

Córcoles, A.D.; Magesan, Easwar; Srinivasan, Srikanth J.; Cross, Andrew W.; Steffen, M.; Gambetta, Jay M.; Chow, Jerry M.

2015-01-01

The ability to detect and deal with errors when manipulating quantum systems is a fundamental requirement for fault-tolerant quantum computing. Unlike classical bits that are subject to only digital bit-flip errors, quantum bits are susceptible to a much larger spectrum of errors, for which any complete quantum error-correcting code must account. Whilst classical bit-flip detection can be realized via a linear array of qubits, a general fault-tolerant quantum error-correcting code requires extending into a higher-dimensional lattice. Here we present a quantum error detection protocol on a two-by-two planar lattice of superconducting qubits. The protocol detects an arbitrary quantum error on an encoded two-qubit entangled state via quantum non-demolition parity measurements on another pair of error syndrome qubits. This result represents a building block towards larger lattices amenable to fault-tolerant quantum error correction architectures such as the surface code. PMID:25923200

Demonstration of a quantum error detection code using a square lattice of four superconducting qubits.

PubMed

Córcoles, A D; Magesan, Easwar; Srinivasan, Srikanth J; Cross, Andrew W; Steffen, M; Gambetta, Jay M; Chow, Jerry M

2015-04-29

The ability to detect and deal with errors when manipulating quantum systems is a fundamental requirement for fault-tolerant quantum computing. Unlike classical bits that are subject to only digital bit-flip errors, quantum bits are susceptible to a much larger spectrum of errors, for which any complete quantum error-correcting code must account. Whilst classical bit-flip detection can be realized via a linear array of qubits, a general fault-tolerant quantum error-correcting code requires extending into a higher-dimensional lattice. Here we present a quantum error detection protocol on a two-by-two planar lattice of superconducting qubits. The protocol detects an arbitrary quantum error on an encoded two-qubit entangled state via quantum non-demolition parity measurements on another pair of error syndrome qubits. This result represents a building block towards larger lattices amenable to fault-tolerant quantum error correction architectures such as the surface code.

Proceedings of the 9th International Symposium on Foundations of Quantum Mechanics in the Light of New Technology

NASA Astrophysics Data System (ADS)

Ishioka, Sachio; Fujikawa, Kazuo

2009-06-01

Committee -- Obituary: Professor Sadao Nakajima -- Opening address / H. Fukuyama -- Welcoming address / N. Osakabe -- Cold atoms and molecules. Pseudopotential method in cold atom research / C. N. Yang. Symmetry breaking in Bose-Einstein condensates / M. Ueda. Quantized vortices in atomic Bose-Einstein condensates / M. Tsubota. Quantum degenerate gases of Ytterbium atoms / S. Uetake ... [et al.]. Superfluid properties of an ultracold fermi gas in the BCS-BEC crossover region / Y. Ohashi, N. Fukushima. Fermionic superfluidity and the BEC-BCS crossover in ultracold atomic fermi gases / M. W. Zwierlein. Kibble-Zurek mechanism in magnetization of a spinor Bose-Einstein condensate / H. Saito, Y. Kawaguchi, M. Ueda. Quasiparticle inducing Josephson effect in a Bose-Einstein condensate / S. Tsuchiya, Y. Ohashi. Stability of superfluid fermi gases in optical lattices / Y. Yunomae ... [et al.]. Z[symbol] symmetry breaking in multi-band bosonic atoms confined by a two-dimensional harmonic potential / M. Sato, A. Tokuno -- Spin hall effect and anomalous hall effect. Recent advances in anomalous hall effect and spin hall effect / N. Nagaosa. Topological insulators and the quantum spin hall effect / C. L. Kane. Application of direct and inverse spin-hall effects: electric manipulation of spin relaxation and electric detection of spin currents / K. Ando, E. Saitoh. Novel current pumping mechanism by spin dynamics / A. Takeuchi, K. Hosono, G. Tatara. Quantum spin hall phase in bismuth ultrathin film / S. Murakami. Anomalous hall effect due to the vector chirality / K. Taguchi, G. Tatara. Spin current distributions and spin hall effect in nonlocal magnetic nanostructures / R. Sugano ... [et al.]. New boundary critical phenomenon at the metal-quantum spin hall insulator transition / H. Obuse. On scaling behaviors of anomalous hall conductivity in disordered ferromagnets studied with the coherent potential approximation / S. Onoda -- Magnetic domain wall dynamics and spin related phenomena. Dynamical magnetoelectric effects in multiferroics / Y. Tokura. Exchange-stabilization of spin accumulation in the two-dimensional electron gas with Rashba-type of spin-orbit interaction / H. M. Saarikoski, G. E. W. Bauer. Electronic Aharonov-Casher effect in InGaAs ring arrays / J. Nitta, M. Kohda, T. Bergsten. Microscopic theory of current-spin interaction in ferromagnets / H. Kohno ... [et al.]. Spin-polarized carrier injection effect in ferromagnetic semiconductor / diffusive semiconductor / superconductor junctions / H. Takayanagi ... [et al.]. Low voltage control of ferromagnetism in a semiconductor P-N junction / J. Wunderlich ... [et al.].Measurement of nanosecond-scale spin-transfer torque magnetization switching / K. Ito ... [et al.]. Current-induced domain wall creep in magnetic wires / J. Ieda, S. Maekawa, S. E. Barnes. Pure spin current injection into superconducting niobium wire / K. Ohnishi, T. Kimura, Y. Otani. Switching of a single atomic spin induced by spin injection: a model calculation / S. Kokado, K. Harigaya, A. Sakuma. Spin transfer torque in magnetic tunnel junctions with synthetic ferrimagnetic layers / M. Ichimura ... [et al.]. Gapless chirality excitations in one-dimensional spin-1/2 frustrated magnets / S. Furukawa ... [et al.] -- Dirac fermions in condensed matter. Electronic states of graphene and its multi-layers / T. Ando, M. Koshino. Inter-layer magnetoresistance in multilayer massless dirac fermions system [symbol]-(BEDT-TTF)[symbol]I[symbol] / N. Tajima ... [et al.]. Theory on electronic properties of gapless states in molecular solids [symbol]-(BEDT-TTF)[symbol]I[symbol] / A. Kobayashi, Y. Suzumura, H. Fukuyama. Hall effect and diamagnetism of bismuth / Y. Fuseya, M. Ogata, H. Fukuyama. Quantum Nernst effect in a bismuth single crystal / M. Matsuo ... [et al.] -- Quantum dot systems. Kondo effect and superconductivity in single InAs quantum dots contacted with superconducting leads / S. Tarucha ... [et al.]. Electron transport through a laterally coupled triple quantum dot forming Aharonov-Bohm interferometer / T. Kubo ... [et al.]. Aharonov-Bohm oscillations in parallel coupled vertical double quantum dot / T. Hatano ... [et al.]. Laterally coupled triple self-assembled quantum dots / S. Amaha ... [et al.]. Spectroscopy of charge states of a superconducting single-electron transistor in an engineered electromagnetic environment / E. Abe ... [et al.]. Numerical study of the coulomb blockade in an open quantum dot / Y. Hamamoto, T. Kato. Symmetry in the full counting statistics, the fluctuation theorem and an extension of the Onsager theorem in nonlinear transport regime / Y. Utsumi, K. Saito. Single-artificial-atom lasing and its suppression by strong pumping / J. R. Johansson ... [et al.] -- Entanglement and quantum information processing, qubit manipulations. Photonic entanglement in quantum communication and quantum computation / A. Zeilinger. Quantum non-demolition measurement of a superconducting flux qubit / J. E. Mooij. Atomic physics and quantum information processing with superconducting circuits / F. Nori. Theory of macroscopic quantum dynamics in high-T[symbol] Josephson junctions / S. Kawabata. Silicon isolated double quantum-dot qubit architectures / D. A. Williams ... [et al.]. Controlled polarisation of silicon isolated double quantum dots with remote charge sensing for qubit use / M. G. Tanner ... [et al.].Modelling of charge qubits based on Si/SiO[symbol] double quantum dots / P. Howard, A. D. Andreev, D. A. Williams. InAs based quantum dots for quantum information processing: from fundamental physics to 'plug and play' devices / X. Xu ... [et al.]. Quantum aspects in superconducting qubit readout with Josephson bifurcation amplifier / H. Nakano ... [et al.]. Double-loop Josephson-junction flux qubit with controllable energy gap / Y. Shimazu, Y. Saito, Z. Wada. Noise characteristics of the Fano effect and Fano-Kondo effect in triple quantum dots, aiming at charge qubit detection / T. Tanamoto, Y. Nishi, S. Fujita. Geometric universal single qubit operation of cold two-level atoms / H. Imai, A. Morinaga. Entanglement dynamics in quantum Brownian motion / K. Shiokawa. Coupling superconducting flux qubits using AC magnetic flxues / Y. Liu, F. Nori. Entanglement purification using natural spin chain dynamics and single spin measurements / K. Maruyama, F. Nori. Experimental analysis of spatial qutrit entanglement of down-converted photon pairs / G. Taguchi ... [et al.]. On the phase sensitivity of two path interferometry using path-symmetric N-photon states / H. F. Hofmann. Control of multi-photon coherence using the mixing ratio of down-converted photons and weak coherent light / T. Ono, H. F. Hofmann -- Mechanical properties of confined geometry. Rattling as a novel anharmonic vibration in a solid / Z. Hiroi, J. Yamaura. Micro/nanomechanical systems for information processing / H. Yamaguchi, I. Mahboob -- Precise measurements. Electron phase microscopy for observing superconductivity and magnetism / A. Tonomura. Ratio of the Al[symbol] and Hg[symbol] optical clock frequencies to 17 decimal places / W. M. Itano ... [et al.]. STM and STS observation on titanium-carbide metallofullerenes: [symbol] / N. Fukui ... [et al.]. Single shot measurement of a silicon single electron transistor / T. Ferrus ... [et al.]. Derivation of sensitivity of a Geiger mode APDs detector from a given efficiency to estimate total photon counts / K. Hammura, D. A. Williams -- Novel properties in nano-systems. First principles study of electroluminescence in ultra-thin silicon film / Y. Suwa, S. Saito. First principles nonlinear optical spectroscopy / T. Hamada, T. Ohno. Field-induced disorder and carrier localization in molecular organic transistors / M. Ando ... [et al.]. Switching dynamics in strongly coupled Josephson junctions / H. Kashiwaya ... [et al.]. Towards quantum simulation with planar coulomb crystals / I. M. Buluta, S. Hasegawa -- Fundamental problems in quantum physics. The negative binomial distribution in quantum physics / J. Söderholm, S. Inoue. On the elementary decay process / D. Kouznetsov -- List of participants.

Semiconductor-inspired design principles for superconducting quantum computing.

PubMed

Shim, Yun-Pil; Tahan, Charles

2016-03-17

Superconducting circuits offer tremendous design flexibility in the quantum regime culminating most recently in the demonstration of few qubit systems supposedly approaching the threshold for fault-tolerant quantum information processing. Competition in the solid-state comes from semiconductor qubits, where nature has bestowed some very useful properties which can be utilized for spin qubit-based quantum computing. Here we begin to explore how selective design principles deduced from spin-based systems could be used to advance superconducting qubit science. We take an initial step along this path proposing an encoded qubit approach realizable with state-of-the-art tunable Josephson junction qubits. Our results show that this design philosophy holds promise, enables microwave-free control, and offers a pathway to future qubit designs with new capabilities such as with higher fidelity or, perhaps, operation at higher temperature. The approach is also especially suited to qubits on the basis of variable super-semi junctions.

Nuclear magnetic resonance in high magnetic field: Application to condensed matter physics

NASA Astrophysics Data System (ADS)

Berthier, Claude; Horvatić, Mladen; Julien, Marc-Henri; Mayaffre, Hadrien; Krämer, Steffen

2017-05-01

In this review, we describe the potentialities offered by the nuclear magnetic resonance (NMR) technique to explore at a microscopic level new quantum states of condensed matter induced by high magnetic fields. We focus on experiments realised in resistive (up to 34 T) or hybrid (up to 45 T) magnets, which open a large access to these quantum phase transitions. After an introduction on NMR observables, we consider several topics: quantum spin systems (spin-Peierls transition, spin ladders, spin nematic phases, magnetisation plateaus, and Bose-Einstein condensation of triplet excitations), the field-induced charge density wave (CDW) in high-Tc superconductors, and exotic superconductivity including the Fulde-Ferrel-Larkin-Ovchinnikov superconducting state and the field-induced superconductivity due to the Jaccarino-Peter mechanism.

Observation of measurement-induced entanglement and quantum trajectories of remote superconducting qubits.

PubMed

Roch, N; Schwartz, M E; Motzoi, F; Macklin, C; Vijay, R; Eddins, A W; Korotkov, A N; Whaley, K B; Sarovar, M; Siddiqi, I

2014-05-02

The creation of a quantum network requires the distribution of coherent information across macroscopic distances. We demonstrate the entanglement of two superconducting qubits, separated by more than a meter of coaxial cable, by designing a joint measurement that probabilistically projects onto an entangled state. By using a continuous measurement scheme, we are further able to observe single quantum trajectories of the joint two-qubit state, confirming the validity of the quantum Bayesian formalism for a cascaded system. Our results allow us to resolve the dynamics of continuous projection onto the entangled manifold, in quantitative agreement with theory.

Nonlinear heat transport in ferromagnetic-quantum dot-superconducting systems

NASA Astrophysics Data System (ADS)

Hwang, Sun-Yong; Sánchez, David

2018-03-01

We analyze the heat current traversing a quantum dot sandwiched between a ferromagnetic and a superconducting electrode. The heat flow generated in response to a voltage bias presents rectification as a function of the gate potential applied to the quantum dot. Remarkably, in the thermally driven case the heat shows a strong diode effect with large asymmetry ratios that can be externally tuned with magnetic fields or spin-polarized tunneling. Our results thus demonstrate the importance of hybrid systems as promising candidates for thermal applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao Xiaoqiang; Wang Hongfu; Zhang Shou

We present an approach for implementation of a 1->3 orbital state quantum cloning machine based on the quantum Zeno dynamics via manipulating three rf superconducting quantum interference device (SQUID) qubits to resonantly interact with a superconducting cavity assisted by classical fields. Through appropriate modulation of the coupling constants between rf SQUIDs and classical fields, the quantum cloning machine can be realized within one step. We also discuss the effects of decoherence such as spontaneous emission and the loss of cavity in virtue of master equation. The numerical simulation result reveals that the quantum cloning machine is especially robust against themore » cavity decay, since all qubits evolve in the decoherence-free subspace with respect to cavity decay due to the quantum Zeno dynamics.« less

Neutron detection using the superconducting Nb-based current-biased kinetic inductance detector

NASA Astrophysics Data System (ADS)

Shishido, Hiroaki; Yamaguchi, Hiroyuki; Miki, Yuya; Miyajima, Shigeyuki; Oikawa, Kenichi; Harada, Masahide; Hidaka, Mutsuo; Oku, Takayuki; Arai, Masatoshi; Fujimaki, Akira; Ishida, Takekazu

2017-09-01

We demonstrate neutron detection using a solid-state 3He-free superconducting current-biased kinetic inductance detector (CB-KID), which consists of a superconducting Nb meander line and 10B neutron absorption layer. The CB-KID is based on the transient process of kinetic inductance of Cooper pairs induced by the nuclear reaction between 10B and neutrons. Therefore, the CB-KID can be operated in a wide superconducting region in the bias current-temperature diagram, as demonstrated in this paper. The transient change of the kinetic inductance induces the electromagnetic wave pulse under a DC bias current. The signal propagates along the meander line toward both sides with opposite polarity, where the signal polarity is dominated by the bias current direction. The full width at half maximum of the signals remains on the order of a few tens of ns, which confirms the high-speed operation of our detectors. We determine the neutron incident position within 1.3 mm accuracy in one dimension using the multichannel CB-KIDs.

Emulation of complex open quantum systems using superconducting qubits

NASA Astrophysics Data System (ADS)

Mostame, Sarah; Huh, Joonsuk; Kreisbeck, Christoph; Kerman, Andrew J.; Fujita, Takatoshi; Eisfeld, Alexander; Aspuru-Guzik, Alán

2017-02-01

With quantum computers being out of reach for now, quantum simulators are alternative devices for efficient and accurate simulation of problems that are challenging to tackle using conventional computers. Quantum simulators are classified into analog and digital, with the possibility of constructing "hybrid" simulators by combining both techniques. Here we focus on analog quantum simulators of open quantum systems and address the limit that they can beat classical computers. In particular, as an example, we discuss simulation of the chlorosome light-harvesting antenna from green sulfur bacteria with over 250 phonon modes coupled to each electronic state. Furthermore, we propose physical setups that can be used to reproduce the quantum dynamics of a standard and multiple-mode Holstein model. The proposed scheme is based on currently available technology of superconducting circuits consist of flux qubits and quantum oscillators.

Superconducting quantum simulator for topological order and the toric code

NASA Astrophysics Data System (ADS)

Sameti, Mahdi; Potočnik, Anton; Browne, Dan E.; Wallraff, Andreas; Hartmann, Michael J.

2017-04-01

Topological order is now being established as a central criterion for characterizing and classifying ground states of condensed matter systems and complements categorizations based on symmetries. Fractional quantum Hall systems and quantum spin liquids are receiving substantial interest because of their intriguing quantum correlations, their exotic excitations, and prospects for protecting stored quantum information against errors. Here, we show that the Hamiltonian of the central model of this class of systems, the toric code, can be directly implemented as an analog quantum simulator in lattices of superconducting circuits. The four-body interactions, which lie at its heart, are in our concept realized via superconducting quantum interference devices (SQUIDs) that are driven by a suitably oscillating flux bias. All physical qubits and coupling SQUIDs can be individually controlled with high precision. Topologically ordered states can be prepared via an adiabatic ramp of the stabilizer interactions. Strings of qubit operators, including the stabilizers and correlations along noncontractible loops, can be read out via a capacitive coupling to read-out resonators. Moreover, the available single-qubit operations allow to create and propagate elementary excitations of the toric code and to verify their fractional statistics. The architecture we propose allows to implement a large variety of many-body interactions and thus provides a versatile analog quantum simulator for topological order and lattice gauge theories.

Benchmarking a quantum teleportation protocol in superconducting circuits using tomography and an entanglement witness.

PubMed

Baur, M; Fedorov, A; Steffen, L; Filipp, S; da Silva, M P; Wallraff, A

2012-01-27

Teleportation of a quantum state may be used for distributing entanglement between distant qubits in quantum communication and for quantum computation. Here we demonstrate the implementation of a teleportation protocol, up to the single-shot measurement step, with superconducting qubits coupled to a microwave resonator. Using full quantum state tomography and evaluating an entanglement witness, we show that the protocol generates a genuine tripartite entangled state of all three qubits. Calculating the projection of the measured density matrix onto the basis states of two qubits allows us to reconstruct the teleported state. Repeating this procedure for a complete set of input states we find an average output state fidelity of 86%.

The contribution of bends and constrictions of a superconducting film to the photon detection by a single-photon superconducting detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zotova, A. N., E-mail: zotova@imp.sci-nnov.ru

2016-05-15

The contribution of bends and constrictions by a superconducting film to the detection by a single photon superconducting detector is investigated. It has been shown that, for currents smaller than the minimal detection current of a straight film, the detection efficiency of a film with a constriction attains saturation upon an increase in the current, which coincides qualitatively with the behavior of this dependence observed in the experiment. It has also been found that the effect of bends in the film and the external magnetic field on the detection efficiency for low-energy photons is essential, while for high-energy photons nomore » such influence is observed.« less

Development and testing of a superconducting link for an IR detector

NASA Technical Reports Server (NTRS)

Caton, R.; Selim, R.

1991-01-01

The development and testing of a ceramic superconducting link for an infrared detector is summarized. Areas of study included the materials used, the electrical contacts, radiation and temperature cycling effects, aging, thermal conductivity, and computer models of an ideal link. Materials' samples were processed in a tube furnace at temperatures of 840 C to 865 C for periods up to 17 days and transition temperatures and critical current densities were recorded. The project achieved better quality high superconducting transition temperature material through improved processing and also achieved high quality electrical contacts. Studies on effects of electron irradiation, temperature cycling, and aging on superconducting properties indicate that the materials will be suitable for space applications. Various presentations and publications on the study's results are reported.

0-π phase-controllable thermal Josephson junction

NASA Astrophysics Data System (ADS)

Fornieri, Antonio; Timossi, Giuliano; Virtanen, Pauli; Solinas, Paolo; Giazotto, Francesco

2017-05-01

Two superconductors coupled by a weak link support an equilibrium Josephson electrical current that depends on the phase difference ϕ between the superconducting condensates. Yet, when a temperature gradient is imposed across the junction, the Josephson effect manifests itself through a coherent component of the heat current that flows opposite to the thermal gradient for |ϕ| < π/2 (refs 2-4). The direction of both the Josephson charge and heat currents can be inverted by adding a π shift to ϕ. In the static electrical case, this effect has been obtained in a few systems, for example via a ferromagnetic coupling or a non-equilibrium distribution in the weak link. These structures opened new possibilities for superconducting quantum logic and ultralow-power superconducting computers. Here, we report the first experimental realization of a thermal Josephson junction whose phase bias can be controlled from 0 to π. This is obtained thanks to a superconducting quantum interferometer that allows full control of the direction of the coherent energy transfer through the junction. This possibility, in conjunction with the completely superconducting nature of our system, provides temperature modulations with an unprecedented amplitude of ∼100 mK and transfer coefficients exceeding 1 K per flux quantum at 25 mK. Then, this quantum structure represents a fundamental step towards the realization of caloritronic logic components such as thermal transistors, switches and memory devices. These elements, combined with heat interferometers and diodes, would complete the thermal conversion of the most important phase-coherent electronic devices and benefit cryogenic microcircuits requiring energy management, such as quantum computing architectures and radiation sensors.

High-performance linear arrays of YBa2Cu3O7 superconducting infrared microbolometers on silicon

NASA Astrophysics Data System (ADS)

Johnson, Burgess R.; Foote, Marc C.; Marsh, Holly A.

1995-06-01

Single detectors and linear arrays of microbolometers utilizing the superconducting transition edge of YBa(subscript 2)Cu(subscript 3)O(subscript 7) have been fabricated by micromachining on silicon wafers. A D* of 8 +/- 2 X 10(superscript 9) cm Hz(superscript 1/2)/watt has been measured on a single detector. This is the highest D* reported on any superconducting microbolometer operating at temperatures higher than about 70 K. The NEP of this device was 1.5 X 10(superscript -12) watts/Hz(superscript HLF) at 2 Hz, at a temperature of 80.7 K. The thermal time constant was 105 msec, and the detector area was 140 micrometers X 105 micrometers . The use of batch silicon processing makes fabrication of linear arrays of these detectors relatively straightforward. The measured responsivity of detectors in one such array varied by less than 20% over the 6 mm length of the 64-element linear array. This measurement shows that good uniformity can be achieved at a single operating temperature in a superconductor microbolometer array, even when the superconducting resistive transition is a sharp function of temperature. The thermal detection mechanism of these devices gives them broadband response. This makes them especially useful at long wavelengths (e.g. (lambda) > 20 micrometers ), where they provide very high sensitivity at relatively high operating temperatures.

Superconducting Switch for Fast On-Chip Routing of Quantum Microwave Fields

NASA Astrophysics Data System (ADS)

Pechal, M.; Besse, J.-C.; Mondal, M.; Oppliger, M.; Gasparinetti, S.; Wallraff, A.

2016-08-01

A switch capable of routing microwave signals at cryogenic temperatures is a desirable component for state-of-the-art experiments in many fields of applied physics, including but not limited to quantum-information processing, communication, and basic research in engineered quantum systems. Conventional mechanical switches provide low insertion loss but disturb operation of dilution cryostats and the associated experiments by heat dissipation. Switches based on semiconductors or microelectromechanical systems have a lower thermal budget but are not readily integrated with current superconducting circuits. Here we design and test an on-chip switch built by combining tunable transmission-line resonators with microwave beam splitters. The device is superconducting and as such dissipates a negligible amount of heat. It is compatible with current superconducting circuit fabrication techniques, operates with a bandwidth exceeding 100 MHz, is capable of handling photon fluxes on the order of 1 05 μ s-1 , equivalent to powers exceeding -90 dBm , and can be switched within approximately 6-8 ns. We successfully demonstrate operation of the device in the quantum regime by integrating it on a chip with a single-photon source and using it to route nonclassical itinerant microwave fields at the single-photon level.

Antenna-Coupled Superconducting Tunnel Junctions with Single-Electron Transistor Readout for Detection of Sub-mm Radiation

NASA Technical Reports Server (NTRS)

Stevenson, T. R.; Hsieh, W.-T.; Li, M. J.; Stahle, C. M.; Wollack, E. J.; Schoelkopf, R. J.; Teufel, J.; Krebs, Carolyn (Technical Monitor)

2002-01-01

Antenna-coupled superconducting tunnel junction detectors have the potential for photon-counting sensitivity at sub-mm wavelengths. The device consists of an antenna structure to couple radiation into a small superconducting volume and cause quasiparticle excitations, and a single-electron transistor to measure currents through tunnel junction contacts to the absorber volume. We will describe optimization of device parameters, and recent results on fabrication techniques for producing devices with high yield for detector arrays. We will also present modeling of expected saturation power levels, antenna coupling, and rf multiplexing schemes.

Tests on a 30 kVA class superconducting transformer

NASA Astrophysics Data System (ADS)

Yoneda, E. S.; Tashiro, I.; Morohoshi, M.; Ito, D.

To demonstrate the applicability of superconductors to electric power machines, the present authors made and tested a 30 kVA class single-phase superconducting transformer. The aim of the study was to determine the superconducting transformer properties. Therefore the superconducting transformer has a simple structure, i.e. the primary to secondary voltage ratio is 1:1 and the iron core is immersed in liquid helium. The core loss, evaluated from no-load tests, was 13 W and leakage impedance, obtained by short circuit tests, was 0.02 Ω in accordance with a calculated value. The superconducting transformer showed the limitation effect of fault currents. The authors succeeded in continuous operation with a 0.5 Ω load resistance. These results suggest that efficiency can be 98.5%, if the iron core is located outside the cryostat and if high Tc superconductors are used as current leads. Superconducting windings exhibit training quenches in general. The authors also developed a superconducting transformer quench detector with a third winding around the iron core. The quench detector revealed that the secondary winding quenches before the primary winding.

Controllable Quantum States Mesoscopic Superconductivity and Spintronics (MS+S2006)

NASA Astrophysics Data System (ADS)

Takayanagi, Hideaki; Nitta, Junsaku; Nakano, Hayato

2008-10-01

Mesoscopic effects in superconductors. Tunneling measurements of charge imbalance of non-equilibrium superconductors / R. Yagi. Influence of magnetic impurities on Josephson current in SNS junctions / T. Yokoyama. Nonlinear response and observable signatures of equilibrium entanglement / A. M. Zagoskin. Stimulated Raman adiabatic passage with a Cooper pair box / Giuseppe Falci. Crossed Andreev reflection-induced giant negative magnetoresistance / Francesco Giazotto -- Quantum modulation of superconducting junctions. Adiabatic pumping through a Josephson weak link / Fabio Taddei. Squeezing of superconducting qubits / Kazutomu Shiokawa. Detection of Berrys phases in flux qubits with coherent pulses / D. N. Zheng. Probing entanglement in the system of coupled Josephson qubits / A. S. Kiyko. Josephson junction with tunable damping using quasi-particle injection / Ryuta Yagi. Macroscopic quantum coherence in rf-SQUIDs / Alexey V. Ustinov. Bloch oscillations in a Josephson circuit / D. Esteve. Manipulation of magnetization in nonequilibrium superconducting nanostructures / F. Giazotto -- Superconducting qubits. Decoherence and Rabi oscillations in a qubit coupled to a quantum two-level system / Sahel Ashhab. Phase-coupled flux qubits: CNOT operation, controllable coupling and entanglement / Mun Dae Kim. Characteristics of a switchable superconducting flux transformer with a DC-SQUID / Yoshihiro Shimazu. Characterization of adiabatic noise in charge-based coherent nanodevices / E. Paladino -- Unconventional superconductors. Threshold temperatures of zero-bias conductance peak and zero-bias conductance dip in diffusive normal metal/superconductor junctions / Iduru Shigeta. Tunneling conductance in 2DEG/S junctions in the presence of Rashba spin-orbit coupling / T. Yokoyama. Theory of charge transport in diffusive ferromagnet/p-wave superconductor junctions / T. Yokoyama. Theory of enhanced proximity effect by the exchange field in FS bilayers / T. Yokoyama. Theory of Josephson effect in diffusive d-wave junctions / T. Yokoyama. Quantum dissipation due to the zero energy bound states in high-T[symbol] superconductor junctions / Shiro Kawabata. Spin-polarized heat transport in ferromagnet/unconventional superconductor junctions / T. Yokoyama. Little-Parks oscillations in chiral p-wave superconducting rings / Mitsuaki Takigawa. Theoretical study of synergy effect between proximity effect and Andreev interface resonant states in triplet p-wave superconductors / Yasunari Tanuma. Theory of proximity effect in unconventional superconductor junctions / Y. Tanaka -- Quantum information. Analyzing the effectiveness of the quantum repeater / Kenichiro Furuta. Architecture-dependent execution time of Shor's algorithm / Rodney Van Meter -- Quantum dots and Kondo effects. Coulomb blockade properties of 4-gated quantum dot / Shinichi Amaha. Order-N electronic structure calculation of n-type GaAs quantum dots / Shintaro Nomura. Transport through double-dots coupled to normal and superconducting leads / Yoichi Tanaka. A study of the quantum dot in application to terahertz single photon counting / Vladimir Antonov. Electron transport through laterally coupled double quantum dots / T. Kubo. Dephasing in Kondo systems: comparison between theory and experiment / F. Mallet. Kondo effect in quantum dots coupled with noncollinear ferromagnetic leads / Daisuke Matsubayashi. Non-crossing approximation study of multi-orbital Kondo effect in quantum dot systems / Tomoko Kita. Theoretical study of electronic states and spin operation in coupled quantum dots / Mikio Eto. Spin correlation in a double quantum dot-quantum wire coupled system / S. Sasaki. Kondo-assisted transport through a multiorbital quantum dot / Rui Sakano. Spin decay in a quantum dot coupled to a quantum point contact / Massoud Borhani -- Quantum wires, low-dimensional electrons. Control of the electron density and electric field with front and back gates / Masumi Yamaguchi. Effect of the array distance on the magnetization configuration of submicron-sized ferromagnetic rings / Tetsuya Miyawaki. A wide GaAs/GaAlAs quantum well simultaneously containing two dimensional electrons and holes / Ane Jensen. Simulation of the photon-spin quantum state transfer process / Yoshiaki Rikitake. Magnetotransport in two-dimensional electron gases on cylindrical surface / Friedland Klaus-Juergen. Full counting statistics for a single-electron transistor at intermediate conductance / Yasuhiro Utsumi. Creation of spin-polarized current using quantum point contacts and its detection / Mikio Eto. Density dependent electron effective mass in a back-gated quantum well / S. Nomura. The supersymmetric sigma formula and metal-insulator transition in diluted magnetic semiconductors / I. Kanazawa. Spin-photovoltaic effect in quantum wires / A. Fedorov -- Quantum interference. Nonequilibrium transport in Aharonov-Bohm interferometer with electron-phonon interaction / Akiko Ueda. Fano resonance and its breakdown in AB ring embedded with a molecule / Shigeo Fujimoto, Yuhei Natsume. Quantum resonance above a barrier in the presence of dissipation / Kohkichi Konno. Ensemble averaging in metallic quantum networks / F. Mallet -- Coherence and order in exotic materials. Progress towards an electronic array on liquid helium / David Rees. Measuring noise and cross correlations at high frequencies in nanophysics / T. Martin. Single wall carbon nanotube weak links / K. Grove-Rasmussen. Optical preparation of nuclear spins coupled to a localized electron spin / Guido Burkard. Topological effects in charge density wave dynamics / Toru Matsuura. Studies on nanoscale charge-density-wave systems: fabrication technique and transport phenomena / Katsuhiko Inagaki. Anisotropic behavior of hysteresis induced by the in-plane field in the v = 2/3 quantum Hall state / Kazuki Iwata. Phase diagram of the v = 2 bilayer quantum Hall state / Akira Fukuda -- Trapped ions (special talk). Quantum computation with trapped ions / Hartmut Häffner.

Method of making superconducting cylinders for flux detectors

DOEpatents

Goodkind, J.M.; Stolfa, D.L.

1971-07-06

A method of making superconducting cylinders of the ''weak link'' type is provided. The method allows the weak link to be made much smaller than was heretofore possible, thereby greatly increasing sensitivity and operating temperature range when the cylinder is used in a flux detector. The resistance of the weak link is monitored continuously as metal is removed from the link by electrochemical action.

Recent advances in superconducting nanowire single photon detectors for single-photon imaging

NASA Astrophysics Data System (ADS)

Verma, V. B.; Allman, M. S.; Stevens, M.; Gerrits, T.; Horansky, R. D.; Lita, A. E.; Marsili, F.; Beyer, A.; Shaw, M. D.; Stern, J. A.; Mirin, R. P.; Nam, S. W.

2016-05-01

We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce the number of readout lines to 16. The cryogenic, optical, and electronic packaging to read out the array, as well as characterization measurements are discussed.

Measurement-induced long-distance entanglement of superconducting qubits using optomechanical transducers

NASA Astrophysics Data System (ADS)

Černotík, Ondřej; Hammerer, Klemens

2016-07-01

Although superconducting systems provide a promising platform for quantum computing, their networking poses a challenge because they cannot be interfaced to light, the medium used to send quantum signals through channels at room temperature. We show that mechanical oscillators can mediate such coupling and light can be used to measure the joint state of two distant qubits. The measurement provides information on the total spin of the two qubits such that entangled qubit states can be postselected. Entanglement generation is possible without ground-state cooling of the mechanical oscillators for systems with optomechanical cooperativity moderately larger than unity; in addition, our setup tolerates a substantial transmission loss. The approach is scalable to the generation of multipartite entanglement and represents a crucial step towards quantum networks with superconducting circuits.

Spin-sensitive interference due to Majorana state on the interface between normal and superconducting leads

NASA Astrophysics Data System (ADS)

Barański, J.; Kobiałka, A.; Domański, T.

2017-02-01

We investigate the subgap spectrum and transport properties of the quantum dot on the interface between the metallic and superconducting leads and additionally side-coupled to the edge of the topological superconducting (TS) chain, hosting the Majorana quasiparticle. Due to the chiral nature of the Majorana states only one spin component of the quantum dot electrons (say \\uparrow ) is directly affected, however the proximity induced on-dot pairing transmits its influence on the opposite spin as well. We investigate the unique interferometric patterns driven by the Majorana quasiparticle that are different for each spin component. We also address the spin-sensitive interplay with the Kondo effect manifested at the same zero-energy and we come to the conclusion that quantum interferometry can unambiguously identify the Majorana quasiparticle.

Development of silicon detectors for Beam Loss Monitoring at HL-LHC

NASA Astrophysics Data System (ADS)

Verbitskaya, E.; Eremin, V.; Zabrodskii, A.; Bogdanov, A.; Shepelev, A.; Dehning, B.; Bartosik, M. R.; Alexopoulos, A.; Glaser, M.; Ravotti, F.; Sapinski, M.; Härkönen, J.; Egorov, N.; Galkin, A.

2017-03-01

Silicon detectors were proposed as novel Beam Loss Monitors (BLM) for the control of the radiation environment in the vicinity of the superconductive magnets of the High-Luminosity Large Hadron Collider. The present work is aimed at enhancing the BLM sensitivity and therefore the capability of triggering the beam abort system before a critical radiation load hits the superconductive coils. We report here the results of three in situ irradiation tests of Si detectors carried out at the CERN PS at 1.9-4.2 K. The main experimental result is that all silicon detectors survived irradiation up to 1.22× 1016 p/cm2. The third test, focused on the detailed characterization of the detectors with standard (300 μm) and reduced (100 μm) thicknesses, showed only a marginal difference in the sensitivity of thinned detectors in the entire fluence range and a smaller rate of signal degradation that promotes their use as BLMs. The irradiation campaigns produced new information on radiation damage and carrier transport in Si detectors irradiated at the temperatures of 1.9-4.2 K. The results were encouraging and permitted to initiate the production of the first BLM prototype modules which were installed at the end of the vessel containing the superconductive coil of a LHC magnet immersed in superfluid helium to be able to test the silicon detectors in real operational conditions.

Bias sputtered NbN and superconducting nanowire devices

NASA Astrophysics Data System (ADS)

Dane, Andrew E.; McCaughan, Adam N.; Zhu, Di; Zhao, Qingyuan; Kim, Chung-Soo; Calandri, Niccolo; Agarwal, Akshay; Bellei, Francesco; Berggren, Karl K.

2017-09-01

Superconducting nanowire single photon detectors (SNSPDs) promise to combine near-unity quantum efficiency with >100 megacounts per second rates, picosecond timing jitter, and sensitivity ranging from x-ray to mid-infrared wavelengths. However, this promise is not yet fulfilled, as superior performance in all metrics is yet to be combined into one device. The highest single-pixel detection efficiency and the widest bias windows for saturated quantum efficiency have been achieved in SNSPDs based on amorphous materials, while the lowest timing jitter and highest counting rates were demonstrated in devices made from polycrystalline materials. Broadly speaking, the amorphous superconductors that have been used to make SNSPDs have higher resistivities and lower critical temperature (Tc) values than typical polycrystalline materials. Here, we demonstrate a method of preparing niobium nitride (NbN) that has lower-than-typical superconducting transition temperature and higher-than-typical resistivity. As we will show, NbN deposited onto unheated SiO2 has a low Tc and high resistivity but is too rough for fabricating unconstricted nanowires, and Tc is too low to yield SNSPDs that can operate well at liquid helium temperatures. By adding a 50 W RF bias to the substrate holder during sputtering, the Tc of the unheated NbN films was increased by up to 73%, and the roughness was substantially reduced. After optimizing the deposition for nitrogen flow rates, we obtained 5 nm thick NbN films with a Tc of 7.8 K and a resistivity of 253 μΩ cm. We used this bias sputtered room temperature NbN to fabricate SNSPDs. Measurements were performed at 2.5 K using 1550 nm light. Photon count rates appeared to saturate at bias currents approaching the critical current, indicating that the device's quantum efficiency was approaching unity. We measured a single-ended timing jitter of 38 ps. The optical coupling to these devices was not optimized; however, integration with front-side optical structures to improve absorption should be straightforward. This material preparation was further used to fabricate nanocryotrons and a large-area imager device, reported elsewhere. The simplicity of the preparation and promising device performance should enable future high-performance devices.

Experimental Demonstration of Fault-Tolerant State Preparation with Superconducting Qubits.

PubMed

Takita, Maika; Cross, Andrew W; Córcoles, A D; Chow, Jerry M; Gambetta, Jay M

2017-11-03

Robust quantum computation requires encoding delicate quantum information into degrees of freedom that are hard for the environment to change. Quantum encodings have been demonstrated in many physical systems by observing and correcting storage errors, but applications require not just storing information; we must accurately compute even with faulty operations. The theory of fault-tolerant quantum computing illuminates a way forward by providing a foundation and collection of techniques for limiting the spread of errors. Here we implement one of the smallest quantum codes in a five-qubit superconducting transmon device and demonstrate fault-tolerant state preparation. We characterize the resulting code words through quantum process tomography and study the free evolution of the logical observables. Our results are consistent with fault-tolerant state preparation in a protected qubit subspace.

Quantum Memristors with Superconducting Circuits

PubMed Central

Salmilehto, J.; Deppe, F.; Di Ventra, M.; Sanz, M.; Solano, E.

2017-01-01

Memristors are resistive elements retaining information of their past dynamics. They have garnered substantial interest due to their potential for representing a paradigm change in electronics, information processing and unconventional computing. Given the advent of quantum technologies, a design for a quantum memristor with superconducting circuits may be envisaged. Along these lines, we introduce such a quantum device whose memristive behavior arises from quasiparticle-induced tunneling when supercurrents are cancelled. For realistic parameters, we find that the relevant hysteretic behavior may be observed using current state-of-the-art measurements of the phase-driven tunneling current. Finally, we develop suitable methods to quantify memory retention in the system. PMID:28195193

Driven superconducting quantum circuits

NASA Astrophysics Data System (ADS)

Nakamura, Yasunobu

2014-03-01

Driven nonlinear quantum systems show rich phenomena in various fields of physics. Among them, superconducting quantum circuits have very attractive features such as well-controlled quantum states with design flexibility, strong nonlinearity of Josephson junctions, strong coupling to electromagnetic driving fields, little internal dissipation, and tailored coupling to the electromagnetic environment. We have investigated properties and functionalities of driven superconducting quantum circuits. A transmon qubit coupled to a transmission line shows nearly perfect spatial mode matching between the incident and scattered microwave field in the 1D mode. Dressed states under a driving field are studied there and also in a semi-infinite 1D mode terminated by a resonator containing a flux qubit. An effective Λ-type three-level system is realized under an appropriate driving condition. It allows ``impedance-matched'' perfect absorption of incident probe photons and down conversion into another frequency mode. Finally, the weak signal from the qubit is read out using a Josephson parametric amplifier/oscillator which is another nonlinear circuit driven by a strong pump field. This work was partly supported by the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST), Project for Developing Innovation Systems of MEXT, MEXT KAKENHI ``Quantum Cybernetics,'' and the NICT Commissioned Research.

Emulating Many-Body Localization with a Superconducting Quantum Processor

NASA Astrophysics Data System (ADS)

Xu, Kai; Chen, Jin-Jun; Zeng, Yu; Zhang, Yu-Ran; Song, Chao; Liu, Wuxin; Guo, Qiujiang; Zhang, Pengfei; Xu, Da; Deng, Hui; Huang, Keqiang; Wang, H.; Zhu, Xiaobo; Zheng, Dongning; Fan, Heng

2018-02-01

The law of statistical physics dictates that generic closed quantum many-body systems initialized in nonequilibrium will thermalize under their own dynamics. However, the emergence of many-body localization (MBL) owing to the interplay between interaction and disorder, which is in stark contrast to Anderson localization, which only addresses noninteracting particles in the presence of disorder, greatly challenges this concept, because it prevents the systems from evolving to the ergodic thermalized state. One critical evidence of MBL is the long-time logarithmic growth of entanglement entropy, and a direct observation of it is still elusive due to the experimental challenges in multiqubit single-shot measurement and quantum state tomography. Here we present an experiment fully emulating the MBL dynamics with a 10-qubit superconducting quantum processor, which represents a spin-1 /2 X Y model featuring programmable disorder and long-range spin-spin interactions. We provide essential signatures of MBL, such as the imbalance due to the initial nonequilibrium, the violation of eigenstate thermalization hypothesis, and, more importantly, the direct evidence of the long-time logarithmic growth of entanglement entropy. Our results lay solid foundations for precisely simulating the intriguing physics of quantum many-body systems on the platform of large-scale multiqubit superconducting quantum processors.

Impact of Disorder on the Superconducting Phase Diagram in BaFe2(As1-xPx)2

NASA Astrophysics Data System (ADS)

Mizukami, Yuta; Konczykowski, Marcin; Matsuura, Kohei; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada

2017-08-01

In many classes of unconventional superconductors, the question of whether the superconductivity is enhanced by the quantum-critical fluctuations on the verge of an ordered phase remains elusive. One of the most direct ways of addressing this issue is to investigate how the superconducting dome traces a shift of the ordered phase. Here, we study how the phase diagram of the iron-based superconductor BaFe2(As1-xPx)2 changes with disorder via electron irradiation, which keeps the carrier concentrations intact. With increasing disorder, we find that the magneto-structural transition is suppressed, indicating that the critical concentration is shifted to the lower side. Although the superconducting transition temperature Tc is depressed at high concentrations (x ≳ 0.28), it shows an initial increase at lower x. This implies that the superconducting dome tracks the shift of the antiferromagnetic phase, supporting the view of the crucial role played by quantum-critical fluctuations in enhancing superconductivity in this iron-based high-Tc family.

Rugged superconducting detector for monitoring infrared energy sources in harsh environments

NASA Astrophysics Data System (ADS)

Laviano, F.; Gerbaldo, R.; Ghigo, G.; Gozzelino, L.; Minetti, B.; Rovelli, A.; Mezzetti, E.

2010-12-01

Broadband electromagnetic characterization of hot plasmas, such as in nuclear fusion reactors and related experiments, requires detecting systems that must withstand high flux of particles and electromagnetic radiations. We propose a rugged layout of a high temperature superconducting detector aimed at 3 THz collective Thomson scattering (CTS) spectroscopy in hot fusion plasma. The YBa2Cu3O7 - x superconducting film is patterned by standard photolithography and the sensing area of the device is created by means of high-energy heavy ion irradiation, in order to modify the crystal structure both of the superconducting film and of the substrate. This method diminishes process costs and resulting device fragility due to membrane or air-bridge structures that are commonly needed for MIR and FIR radiation detection. Moreover the sensing area of the device is wired by the same superconducting material and thus excellent mechanical strength is exhibited by the whole device, due to the oxide substrate. Continuous wave operation of prototype devices is demonstrated at liquid nitrogen temperature, for selected infrared spectra of broadband thermal energy sources. Several solutions, which exploit the advantages coming from the robustness of this layout in terms of intrinsic radiation hardness of the superconducting material and of the needed optical components, are analysed with reference to applications of infrared electromagnetic detectors in a tokamak machine environment.

Superconductivity mediated by quantum critical antiferromagnetic fluctuations: the rise and fall of hot spots

NASA Astrophysics Data System (ADS)

Wang, Xiaoyu; Schattner, Yoni; Berg, Erez; Fernandes, Rafael

The maximum transition temperature Tc observed in the phase diagrams of several unconventional superconductors takes place in the vicinity of a putative antiferromagnetic quantum critical point. This observation motivated the theoretical proposal that superconductivity in these systems may be driven by quantum critical fluctuations, which in turn can also promote non-Fermi liquid behavior. In this talk, we present a combined analytical and sign-problem-free Quantum Monte Carlo investigation of the spin-fermion model - a widely studied low-energy model for the interplay between superconductivity and magnetic fluctuations. By engineering a series of band dispersions that interpolate between near-nested and open Fermi surfaces, and by also varying the strength of the spin-fermion interaction, we find that the hot spots of the Fermi surface provide the dominant contribution to the pairing instability in this model. We show that the analytical expressions for Tc and for the pairing susceptibility, obtained within a large-N Eliashberg approximation to the spin-fermion model, agree well with the Quantum Monte Carlo data, even in the regime of interactions comparable to the electronic bandwidth. DE-SC0012336.

Interfacing planar superconducting qubits with high overtone bulk acoustic phonons

NASA Astrophysics Data System (ADS)

Kervinen, Mikael; Rissanen, Ilkka; Sillanpää, Mika

2018-05-01

Mechanical resonators are a promising way for interfacing qubits in order to realize hybrid quantum systems that offer great possibilities for applications. Mechanical systems can have very long energy lifetimes, and they can be further interfaced to other systems. Moreover, integration of a mechanical oscillator with qubits creates a potential platform for the exploration of quantum physics in macroscopic mechanical degrees of freedom. The utilization of high overtone bulk acoustic resonators coupled to superconducting qubits is an intriguing platform towards these goals. These resonators exhibit a combination of high-frequency and high-quality factors. They can reach their quantum ground state at dilution refrigeration temperatures and they can be strongly coupled to superconducting qubits via their piezoelectric effect. In this paper, we demonstrate our system where bulk acoustic phonons of a high overtone resonator are coupled to a transmon qubit in a planar circuit architecture. We show that the bulk acoustic phonons are interacting with the qubit in a simple design architecture at the quantum level, representing further progress towards the quantum control of mechanical motion.

Digital-analog quantum simulation of generalized Dicke models with superconducting circuits

NASA Astrophysics Data System (ADS)

Lamata, Lucas

We propose a digital-analog quantum simulation of generalized Dicke models with superconducting circuits, including Fermi-Bose condensates, biased and pulsed Dicke models, for all regimes of light-matter coupling. We encode these classes of problems in a set of superconducting qubits coupled with a bosonic mode implemented by a transmission line resonator. Via digital-analog techniques, an efficient quantum simulation can be performed in state-of-the-art circuit quantum electrodynamics platforms, by suitable decomposition into analog qubit-bosonic blocks and collective single-qubit pulses through digital steps. Moreover, just a single global analog block would be needed during the whole protocol in most of the cases, superimposed with fast periodic pulses to rotate and detune the qubits. Therefore, a large number of digital steps may be attained with this approach, providing a reduced digital error. Additionally, the number of gates per digital step does not grow with the number of qubits, rendering the simulation efficient. This strategy paves the way for the scalable digital-analog quantum simulation of many-body dynamics involving bosonic modes and spin degrees of freedom with superconducting circuits. The author wishes to acknowledge discussions with I. Arrazola, A. Mezzacapo, J. S. Pedernales, and E. Solano, and support from Ramon y Cajal Grant RYC-2012-11391, Spanish MINECO/FEDER FIS2015-69983-P, UPV/EHU UFI 11/55 and Project EHUA14/04.

Quantum Well and Quantum Dot Modeling for Advanced Infrared Detectors and Focal Plane Arrays

NASA Technical Reports Server (NTRS)

Ting, David; Gunapala, S. D.; Bandara, S. V.; Hill, C. J.

2006-01-01

This viewgraph presentation reviews the modeling of Quantum Well Infrared Detectors (QWIP) and Quantum Dot Infrared Detectors (QDIP) in the development of Focal Plane Arrays (FPA). The QWIP Detector being developed is a dual band detector. It is capable of running on two bands Long-Wave Infrared (LWIR) and Medium Wavelength Infrared (MWIR). The same large-format dual-band FPA technology can be applied to Quantum Dot Infrared Photodetector (QDIP) with no modification, once QDIP exceeds QWIP in single device performance. Details of the devices are reviewed.

Epitaxy of advanced nanowire quantum devices

NASA Astrophysics Data System (ADS)

Gazibegovic, Sasa; Car, Diana; Zhang, Hao; Balk, Stijn C.; Logan, John A.; de Moor, Michiel W. A.; Cassidy, Maja C.; Schmits, Rudi; Xu, Di; Wang, Guanzhong; Krogstrup, Peter; Op Het Veld, Roy L. M.; Zuo, Kun; Vos, Yoram; Shen, Jie; Bouman, Daniël; Shojaei, Borzoyeh; Pennachio, Daniel; Lee, Joon Sue; van Veldhoven, Petrus J.; Koelling, Sebastian; Verheijen, Marcel A.; Kouwenhoven, Leo P.; Palmstrøm, Chris J.; Bakkers, Erik P. A. M.

2017-08-01

Semiconductor nanowires are ideal for realizing various low-dimensional quantum devices. In particular, topological phases of matter hosting non-Abelian quasiparticles (such as anyons) can emerge when a semiconductor nanowire with strong spin-orbit coupling is brought into contact with a superconductor. To exploit the potential of non-Abelian anyons—which are key elements of topological quantum computing—fully, they need to be exchanged in a well-controlled braiding operation. Essential hardware for braiding is a network of crystalline nanowires coupled to superconducting islands. Here we demonstrate a technique for generic bottom-up synthesis of complex quantum devices with a special focus on nanowire networks with a predefined number of superconducting islands. Structural analysis confirms the high crystalline quality of the nanowire junctions, as well as an epitaxial superconductor-semiconductor interface. Quantum transport measurements of nanowire ‘hashtags’ reveal Aharonov-Bohm and weak-antilocalization effects, indicating a phase-coherent system with strong spin-orbit coupling. In addition, a proximity-induced hard superconducting gap (with vanishing sub-gap conductance) is demonstrated in these hybrid superconductor-semiconductor nanowires, highlighting the successful materials development necessary for a first braiding experiment. Our approach opens up new avenues for the realization of epitaxial three-dimensional quantum architectures which have the potential to become key components of various quantum devices.

Deterministic entanglement of superconducting qubits by parity measurement and feedback.

PubMed

Ristè, D; Dukalski, M; Watson, C A; de Lange, G; Tiggelman, M J; Blanter, Ya M; Lehnert, K W; Schouten, R N; DiCarlo, L

2013-10-17

The stochastic evolution of quantum systems during measurement is arguably the most enigmatic feature of quantum mechanics. Measuring a quantum system typically steers it towards a classical state, destroying the coherence of an initial quantum superposition and the entanglement with other quantum systems. Remarkably, the measurement of a shared property between non-interacting quantum systems can generate entanglement, starting from an uncorrelated state. Of special interest in quantum computing is the parity measurement, which projects the state of multiple qubits (quantum bits) to a state with an even or odd number of excited qubits. A parity meter must discern the two qubit-excitation parities with high fidelity while preserving coherence between same-parity states. Despite numerous proposals for atomic, semiconducting and superconducting qubits, realizing a parity meter that creates entanglement for both even and odd measurement results has remained an outstanding challenge. Here we perform a time-resolved, continuous parity measurement of two superconducting qubits using the cavity in a three-dimensional circuit quantum electrodynamics architecture and phase-sensitive parametric amplification. Using postselection, we produce entanglement by parity measurement reaching 88 per cent fidelity to the closest Bell state. Incorporating the parity meter in a feedback-control loop, we transform the entanglement generation from probabilistic to fully deterministic, achieving 66 per cent fidelity to a target Bell state on demand. These realizations of a parity meter and a feedback-enabled deterministic measurement protocol provide key ingredients for active quantum error correction in the solid state.

Protecting quantum information in superconducting circuits

NASA Astrophysics Data System (ADS)

Devoret, Michel

Can we prolong the coherence of a two-state manifold in a complex quantum system beyond the coherence of its longest-lived component? This question is the starting point in the construction of a scalable quantum computer. It translates in the search for processes that operate as some sort of Maxwell's demon and reliably correct the errors resulting from the coupling between qubits and their environment. The presentation will review recent experiments that test the dynamical protection by Josephson circuits of a logical qubit memory based on superpositions of particular coherent states of a superconducting resonator.

Superconducting Quantum Arrays for Wideband Antennas and Low Noise Amplifiers

NASA Technical Reports Server (NTRS)

Mukhanov, O.; Prokopemko, G.; Romanofsky, Robert R.

2014-01-01

Superconducting Quantum Iinetference Filters (SQIF) consist of a two-dimensional array of niobium Josephson Junctions formed into N loops of incommensurate area. This structure forms a magnetic field (B) to voltage transducer with an impulse like response at B0. In principle, the signal-to-noise ratio scales as the square root of N and the noise can be made arbitrarily small (i.e. The SQIF chips are expected to exhibit quantum limited noise performance). A gain of about 20 dB was recently demonstrated at 10 GHz.

Emerging superconductivity hidden beneath charge-transfer insulators

PubMed Central

Krockenberger, Yoshiharu; Irie, Hiroshi; Matsumoto, Osamu; Yamagami, Keitaro; Mitsuhashi, Masaya; Tsukada, Akio; Naito, Michio; Yamamoto, Hideki

2013-01-01

In many of today's most interesting materials, strong interactions prevail upon the magnetic moments, the electrons, and the crystal lattice, forming strong links between these different aspects of the system. Particularly, in two-dimensional cuprates, where copper is either five- or six-fold coordinated, superconductivity is commonly induced by chemical doping which is deemed to be mandatory by destruction of long-range antiferromagnetic order of 3d9 Cu2+ moments. Here we show that superconductivity can be induced in Pr2CuO4, where copper is four-fold coordinated. We induced this novel quantum state of Pr2CuO4 by realizing pristine square-planar coordinated copper in the copper-oxygen planes, thus, resulting in critical superconducting temperatures even higher than by chemical doping. Our results demonstrate new degrees of freedom, i.e., coordination of copper, for the manipulation of magnetic and superconducting order parameters in quantum materials. PMID:23887134

Low-Loss Superconducting Nanowire Circuits Using a Neon Focused Ion Beam

NASA Astrophysics Data System (ADS)

Burnett, J.; Sagar, J.; Kennedy, O. W.; Warburton, P. A.; Fenton, J. C.

2017-07-01

We present low-temperature measurements of low-loss superconducting nanowire-embedded resonators in the low-power limit relevant for quantum circuits. The superconducting resonators are embedded with superconducting nanowires with widths down to 20 nm using a neon focused ion beam. In the low-power limit, we demonstrate an internal quality factor up to 3.9 ×105 at 300 mK [implying a two-level-system-limited quality factor up to 2 ×105 at 10 mK], not only significantly higher than in similar devices but also matching the state of the art of conventional Josephson-junction-embedded resonators. We also show a high sensitivity of the nanowire to stray infrared photons, which is controllable by suitable precautions to minimize stray photons in the sample environment. Our results suggest that there are excellent prospects for superconducting-nanowire-based quantum circuits.

Squeezing of magnetic flux in nanorings.

PubMed

Dajka, J; Ptok, A; Luczka, J

2012-12-12

We study superconducting and non-superconducting nanorings and look for non-classical features of magnetic flux passing through nanorings. We show that the magnetic flux can exhibit purely quantum properties in some peculiar states with quadrature squeezing. We identify a subset of Gazeau-Klauder states in which the magnetic flux can be squeezed and, within tailored parameter regimes, quantum fluctuations of the magnetic flux can be maximally reduced.

Superconductivity from a non-Fermi-liquid metal: Kondo fluctuation mechanism in slave-fermion theory

NASA Astrophysics Data System (ADS)

Kim, Ki-Seok

2010-03-01

We propose Kondo fluctuation mechanism of superconductivity, differentiated from the spin-fluctuation theory as the standard model for unconventional superconductivity in the weak-coupling approach. Based on the U(1) slave-fermion representation of an effective Anderson lattice model, where localized spins are described by the Schwinger boson theory and hybridization or Kondo fluctuations weaken antiferromagnetic correlations of localized spins, we found an antiferromagnetic quantum critical point from an antiferromagnetic metal to a heavy-fermion metal in our recent study. The Kondo-induced antiferromagnetic quantum critical point was shown to be described by both conduction electrons and fermionic holons interacting with critical spin fluctuations given by deconfined bosonic spinons with a spin quantum number 1/2. Surprisingly, such critical modes turned out to be described by the dynamical exponent z=3 , giving rise to the well-known non-Fermi-liquid physics such as the divergent Grüneisen ratio with an exponent 2/3 and temperature-linear resistivity in three dimensions. We find that the z=3 antiferromagnetic quantum critical point becomes unstable against superconductivity, where critical spinon excitations give rise to pairing correlations between conduction electrons and between fermionic holons, respectively, via hybridization fluctuations. Such two kinds of pairing correlations result in multigap unconventional superconductivity around the antiferromagnetic quantum critical point of the slave-fermion theory, where s -wave pairing is not favored generically due to strong correlations. We show that the ratio between each superconducting gap for conduction electrons Δc and holons Δf and the transition temperature Tc is 2Δc/Tc˜9 and 2Δf/Tc˜O(10-1) , remarkably consistent with CeCoIn5 . A fingerprint of the Kondo mechanism is emergence of two kinds of resonance modes in not only spin but also charge fluctuations, where the charge resonance mode at an antiferromagnetic wave vector originates from d -wave pairing of spinless holons. We discuss how the Kondo fluctuation theory differs from the spin-fluctuation approach.

Phase-locking transition in a chirped superconducting Josephson resonator.

PubMed

Naaman, O; Aumentado, J; Friedland, L; Wurtele, J S; Siddiqi, I

2008-09-12

We observe a sharp threshold for dynamic phase locking in a high-Q transmission line resonator embedded with a Josephson tunnel junction, and driven with a purely ac, chirped microwave signal. When the drive amplitude is below a critical value, which depends on the chirp rate and is sensitive to the junction critical current I0, the resonator is only excited near its linear resonance frequency. For a larger amplitude, the resonator phase locks to the chirped drive and its amplitude grows until a deterministic maximum is reached. Near threshold, the oscillator evolves smoothly in one of two diverging trajectories, providing a way to discriminate small changes in I0 with a nonswitching detector, with potential applications in quantum state measurement.

Application of SQUIDs to low temperature and high magnetic field measurements—Ultra low noise torque magnetometry

NASA Astrophysics Data System (ADS)

Arnold, F.; Naumann, M.; Lühmann, Th.; Mackenzie, A. P.; Hassinger, E.

2018-02-01

Torque magnetometry is a key method to measure the magnetic anisotropy and quantum oscillations in metals. In order to resolve quantum oscillations in sub-millimeter sized samples, piezo-electric micro-cantilevers were introduced. In the case of strongly correlated metals with large Fermi surfaces and high cyclotron masses, magnetic torque resolving powers in excess of 104 are required at temperatures well below 1 K and magnetic fields beyond 10 T. Here, we present a new broadband read-out scheme for piezo-electric micro-cantilevers via Wheatstone-type resistance measurements in magnetic fields up to 15 T and temperatures down to 200 mK. By using a two-stage superconducting-quantum interference device as a null detector of a cold Wheatstone bridge, we were able to achieve a magnetic moment resolution of Δm = 4 × 10-15 J/T at maximal field and 700 mK, outperforming conventional magnetometers by at least one order of magnitude in this temperature and magnetic field range. Exemplary de Haas-van Alphen measurement of a newly grown delafossite, PdRhO2, was used to show the superior performance of our setup.

On-demand generation of background-free single photons from a solid-state source

NASA Astrophysics Data System (ADS)

Schweickert, Lucas; Jöns, Klaus D.; Zeuner, Katharina D.; Covre da Silva, Saimon Filipe; Huang, Huiying; Lettner, Thomas; Reindl, Marcus; Zichi, Julien; Trotta, Rinaldo; Rastelli, Armando; Zwiller, Val

2018-02-01

True on-demand high-repetition-rate single-photon sources are highly sought after for quantum information processing applications. However, any coherently driven two-level quantum system suffers from a finite re-excitation probability under pulsed excitation, causing undesirable multi-photon emission. Here, we present a solid-state source of on-demand single photons yielding a raw second-order coherence of g(2 )(0 )=(7.5 ±1.6 )×10-5 without any background subtraction or data processing. To this date, this is the lowest value of g(2 )(0 ) reported for any single-photon source even compared to the previously reported best background subtracted values. We achieve this result on GaAs/AlGaAs quantum dots embedded in a low-Q planar cavity by employing (i) a two-photon excitation process and (ii) a filtering and detection setup featuring two superconducting single-photon detectors with ultralow dark-count rates of (0.0056 ±0.0007 ) s-1 and (0.017 ±0.001 ) s-1, respectively. Re-excitation processes are dramatically suppressed by (i), while (ii) removes false coincidences resulting in a negligibly low noise floor.

Transition-Edge Hot-Electron Microbolometers for Millimeter and Submillimeter Astrophysics

NASA Technical Reports Server (NTRS)

Hsieh, Wen-Ting; Stevenson, Thomas; U-yen, Kongpop; Wollack, Edward; Barrentine, Emily

2014-01-01

The millimeter and the submillimeter wavelengths of the electromagnetic spectrum hold a wealth of information about the evolution of the universe. In particular, cosmic microwave background (CMB) radiation and its polarization carry the oldest information in the universe, and provide the best test of the inflationary paradigm available to astronomy today. Detecting gravity waves through their imprint on the CMB polarization would have extraordinary repercussions for cosmology and physics. A transition-edge hot-electron micro - bolometer (THM) consists of a superconducting bilayer transition-edge sensor (TES) with a thin-film absorber. Unlike traditional monolithic bolometers that make use of micromachined structures, the THM em ploys the decoupling between electrons and phonons at millikelvin temperatures to provide thermal isolation. The devices are fabricated photolithographically and are easily integrated with antennas via microstrip transmission lines, and with SQUID (superconducting quantum interference device) readouts. The small volume of the absorber and TES produces a short thermal time constant that facilitates rapid sky scanning. The THM consists of a thin-film metal absorber overlapping a superconducting TES. The absorber forms the termination of a superconducting microstripline that carries RF power from an antenna. The purpose of forming a separate absorber and TES is to allow flexibility in the optimization of the two components. In particular, the absorbing film's impedance can be chosen to match the antenna, while the TES impedance can be chosen to match to the readout SQUID amplifier. This scheme combines the advantages of the TES with the advantages of planar millimeter-wave transmission line circuits. Antenna-coupling to the detectors via planar transmission lines allows the detector dimensions to be much smaller than a wavelength, so the technique can be extended across the entire microwave, millimeter, and submillimeter wavelength ranges. The circuits are fabricated using standard microlithographic techniques and are compatible with uniform, large array formats. Unlike traditional monolithic bolometers that make use of micromachined structures, the THM employs the decoupling between electrons and phonons at millikelvin temperatures to provide thermal isolation. There is no fragile membrane in the structure for thermal isolation, which improves the fabrication yield.

An Investigation into the Electromagnetic Interactions between a Superconducting Torus and Solenoid for the Jefferson Lab 12 GeV Upgrade

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajput-Ghoshal, Renuka; Ghoshal, Probir K.; Fair, Ruben J.

2015-06-01

The Jefferson Lab 12 GeV Upgrade in Hall B will need CLAS12 detector that requires two superconducting magnets. One is a magnet system consisting of six superconducting trapezoidal racetrack-type coils assembled in a Toroidal configuration (Torus) and the second is an actively shielded solenoidal magnet (Solenoid). Both the torus and solenoid are located in close proximity to one another and are surrounded by sensitive detectors. This paper investigates the electromagnetic interactions between the two systems during normal operation as well as during various fault scenarios as part of a Risk Assessment and Mitigation (RAM).

Emulating weak localization using a solid-state quantum circuit.

PubMed

Chen, Yu; Roushan, P; Sank, D; Neill, C; Lucero, Erik; Mariantoni, Matteo; Barends, R; Chiaro, B; Kelly, J; Megrant, A; Mutus, J Y; O'Malley, P J J; Vainsencher, A; Wenner, J; White, T C; Yin, Yi; Cleland, A N; Martinis, John M

2014-10-14

Quantum interference is one of the most fundamental physical effects found in nature. Recent advances in quantum computing now employ interference as a fundamental resource for computation and control. Quantum interference also lies at the heart of sophisticated condensed matter phenomena such as Anderson localization, phenomena that are difficult to reproduce in numerical simulations. Here, employing a multiple-element superconducting quantum circuit, with which we manipulate a single microwave photon, we demonstrate that we can emulate the basic effects of weak localization. By engineering the control sequence, we are able to reproduce the well-known negative magnetoresistance of weak localization as well as its temperature dependence. Furthermore, we can use our circuit to continuously tune the level of disorder, a parameter that is not readily accessible in mesoscopic systems. Demonstrating a high level of control, our experiment shows the potential for employing superconducting quantum circuits as emulators for complex quantum phenomena.

Continuous-variable geometric phase and its manipulation for quantum computation in a superconducting circuit.

PubMed

Song, Chao; Zheng, Shi-Biao; Zhang, Pengfei; Xu, Kai; Zhang, Libo; Guo, Qiujiang; Liu, Wuxin; Xu, Da; Deng, Hui; Huang, Keqiang; Zheng, Dongning; Zhu, Xiaobo; Wang, H

2017-10-20

Geometric phase, associated with holonomy transformation in quantum state space, is an important quantum-mechanical effect. Besides fundamental interest, this effect has practical applications, among which geometric quantum computation is a paradigm, where quantum logic operations are realized through geometric phase manipulation that has some intrinsic noise-resilient advantages and may enable simplified implementation of multi-qubit gates compared to the dynamical approach. Here we report observation of a continuous-variable geometric phase and demonstrate a quantum gate protocol based on this phase in a superconducting circuit, where five qubits are controllably coupled to a resonator. Our geometric approach allows for one-step implementation of n-qubit controlled-phase gates, which represents a remarkable advantage compared to gate decomposition methods, where the number of required steps dramatically increases with n. Following this approach, we realize these gates with n up to 4, verifying the high efficiency of this geometric manipulation for quantum computation.

Magnetic excitations in Kondo liquid: superconductivity and hidden magnetic quantum critical fluctuations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yifeng; Urbano, Ricardo; Nicholas, Curro

2009-01-01

We report Knight shift experiments on the superconducting heavy electron material CeCoIn{sub 5} that allow one to track with some precision the behavior of the heavy electron Kondo liquid in the superconducting state with results in agreement with BCS theory. An analysis of the {sup 115}In nuclear quadrupole resonance (NQR) spin-lattice relaxation rate T{sub 1}{sup -1} measurements under pressure reveals the presence of 2d magnetic quantum critical fluctuations in the heavy electron component that are a promising candidate for the pairing mechanism in this material. Our results are consistent with an antiferromagnetic quantum critical point (QCP) located at slightly negativemore » pressure in CeCoIn{sub 5} and provide additional evidence for significant similarities between the heavy electron materials and the high T{sub c} cuprates.« less

Quantum metallicity on the high-field side of the superconductor-insulator transition.

PubMed

Baturina, T I; Strunk, C; Baklanov, M R; Satta, A

2007-03-23

We investigate ultrathin superconducting TiN films, which are very close to the localization threshold. Perpendicular magnetic field drives the films from the superconducting to an insulating state, with very high resistance. Further increase of the magnetic field leads to an exponential decay of the resistance towards a finite value. In the limit of low temperatures, the saturation value can be very accurately extrapolated to the universal quantum resistance h/e2. Our analysis suggests that at high magnetic fields a new ground state, distinct from the normal metallic state occurring above the superconducting transition temperature, is formed. A comparison with other studies on different materials indicates that the quantum metallic phase following the magnetic-field-induced insulating phase is a generic property of systems close to the disorder-driven superconductor-insulator transition.

Tomography of quantum detectors

NASA Astrophysics Data System (ADS)

Lundeen, J. S.; Feito, A.; Coldenstrodt-Ronge, H.; Pregnell, K. L.; Silberhorn, Ch.; Ralph, T. C.; Eisert, J.; Plenio, M. B.; Walmsley, I. A.

2009-01-01

Measurement connects the world of quantum phenomena to the world of classical events. It has both a passive role-in observing quantum systems-and an active one, in preparing quantum states and controlling them. In view of the central status of measurement in quantum mechanics, it is surprising that there is no general recipe for designing a detector that measures a given observable. Compounding this, the characterization of existing detectors is typically based on partial calibrations or elaborate models. Thus, experimental specification (that is, tomography) of a detector is of fundamental and practical importance. Here, we present the realization of quantum detector tomography. We identify the positive-operator-valued measure describing the detector, with no ancillary assumptions. This result completes the triad, state, process and detector tomography, required to fully specify an experiment. We characterize an avalanche photodiode and a photon-number-resolving detector capable of detecting up to eight photons. This creates a new set of tools for accurately detecting and preparing non-classical light.

Feedhorn-Coupled Transition-Edge Superconducting Bolometer Arrays for Cosmic Microwave Background Polarimetry

NASA Technical Reports Server (NTRS)

Hubmayr, J.; Austermann, J.; Beall, J.; Becker, D.; Cho, H.-M.; Datta, R.; Duff, S. M.; Grace, E.; Halverson, N.; Henderson, S. W.;

Frequency-multiplexed bias and readout of a 16-pixel superconducting nanowire single-photon detector array

NASA Astrophysics Data System (ADS)

Doerner, S.; Kuzmin, A.; Wuensch, S.; Charaev, I.; Boes, F.; Zwick, T.; Siegel, M.

2017-07-01

We demonstrate a 16-pixel array of microwave-current driven superconducting nanowire single-photon detectors with an integrated and scalable frequency-division multiplexing architecture, which reduces the required number of bias and readout lines to a single microwave feed line. The electrical behavior of the photon-sensitive nanowires, embedded in a resonant circuit, as well as the optical performance and timing jitter of the single detectors is discussed. Besides the single pixel measurements, we also demonstrate the operation of a 16-pixel array with a temporal, spatial, and photon-number resolution.

Ultrafast IR detector response in high Tc superconducting thin films

NASA Technical Reports Server (NTRS)

Lindgren, Mikael; Ahlberg, Henrik; Danerud, Martin; Larsson, Anders; Eng, Sverre T.

1991-01-01

The response from a high Tc superconducting multielement optical detector made of a laser deposited Y-Ba-Cu-O thin film has been evaluated. Several microscopic and spectroscopic techniques were used to establish the presence of the correct phase of the thin film. Optical pulses from a laser diode at 830 nm and from a Q-switched CO2-laser at 10.6 microns were used. The detector responded to 50 ps (FWHM) pulses. A comparison between dR/dT of the film and the response amplitude as a function of temperature indicated a bolometric response.

Superconductivity: Technology meets quantum criticality

NASA Astrophysics Data System (ADS)

Zaanen, Jan

2005-09-01

Superconductivity and antiferromagnetism are in fierce competition in high-temperature superconductors. However, this competition has the unexpected benefit that the antiferromagnetism improves the capacity of the superconductor to resist magnetic fields.

A voltage-controlled superconducting quantum bus

NASA Astrophysics Data System (ADS)

Casparis, Lucas; Pearson, Natalie; KringhøJ, Anders; Larsen, Thorvald; Kuemmeth, Ferdinand; Krogstrup, Peter; Nygard, Jesper; Petersson, Karl; Marcus, Charles

Superconducting qubits couple strongly to microwave photons and can therefore be coupled over long distances through a superconducting cavity acting as a quantum bus. To avoid frequency-crowding it is desirable to turn qubit coupling off while rearranging qubit frequencies. Here, we present experiments with two gatemon qubits coupled through a cavity, which can be tuned by a voltage-controlled superconducting switch. We characterize the bus tunability and demonstrate switchable qubit coupling with an on/off ratio up to 8. We find that pulsing the bus switch on nanosecond timescales results in the apparent loss of qubit coherence. Further work is needed to understand how dynamic control of the tuneable bus affects qubit operation. We acknowledge financial support from Microsoft Project Q, the Danish National Research Foundation and the US Army Research Office.

Emergence of superconductivity in the canonical heavy-electron metal YbRh₂Si₂.

PubMed

Schuberth, Erwin; Tippmann, Marc; Steinke, Lucia; Lausberg, Stefan; Steppke, Alexander; Brando, Manuel; Krellner, Cornelius; Geibel, Christoph; Yu, Rong; Si, Qimiao; Steglich, Frank

2016-01-29

The smooth disappearance of antiferromagnetic order in strongly correlated metals commonly furnishes the development of unconventional superconductivity. The canonical heavy-electron compound YbRh2Si2 seems to represent an apparent exception from this quantum critical paradigm in that it is not a superconductor at temperature T ≥ 10 millikelvin (mK). Here we report magnetic and calorimetric measurements on YbRh2Si2, down to temperatures as low as T ≈ 1 mK. The data reveal the development of nuclear antiferromagnetic order slightly above 2 mK and of heavy-electron superconductivity almost concomitantly with this order. Our results demonstrate that superconductivity in the vicinity of quantum criticality is a general phenomenon. Copyright © 2016, American Association for the Advancement of Science.

Tunneling probe of fluctuating superconductivity in disordered thin films

NASA Astrophysics Data System (ADS)

Dentelski, David; Frydman, Aviad; Shimshoni, Efrat; Dalla Torre, Emanuele G.

2018-03-01

Disordered thin films close to the superconductor-insulator phase transition (SIT) hold the key to understanding quantum phase transition in strongly correlated materials. The SIT is governed by superconducting quantum fluctuations, which can be revealed, for example, by tunneling measurements. These experiments detect a spectral gap, accompanied by suppressed coherence peaks, on both sides of the transition. Here we describe the insulating side in terms of a fluctuating superconducting field with finite-range correlations. We perform a controlled diagrammatic resummation and derive analytic expressions for the tunneling differential conductance. We find that short-range superconducting fluctuations suppress the coherence peaks even in the presence of long-range correlations. Our approach offers a quantitative description of existing measurements on disordered thin films and accounts for tunneling spectra with suppressed coherence peaks.

Quantum Memristors with Superconducting Circuits

DOE PAGES

Salmilehto, J.; Deppe, F.; Di Ventra, M.; ...

2017-02-14

Memristors are resistive elements retaining information of their past dynamics. They have garnered substantial interest due to their potential for representing a paradigm change in electronics, information processing and unconventional computing. Given the advent of quantum technologies, a design for a quantum memristor with superconducting circuits may be envisaged. Along these lines, we introduce such a quantum device whose memristive behavior arises from quasiparticle-induced tunneling when supercurrents are cancelled. Here in this paper, for realistic parameters, we find that the relevant hysteretic behavior may be observed using current state-of-the-art measurements of the phase-driven tunneling current. Finally, we develop suitable methodsmore » to quantify memory retention in the system.« less

Performance and Characterization of a Modular Superconducting Nanowire Single Photon Detector System for Space-to-Earth Optical Communications Links

NASA Technical Reports Server (NTRS)

Vyhnalek, Brian E.; Tedder, Sarah A.; Nappier, Jennifer M.

2018-01-01

Space-to-ground photon-counting optical communication links supporting high data rates over large distances require enhanced ground receiver sensitivity in order to reduce the mass and power burden on the spacecraft transmitter. Superconducting nanowire single-photon detectors (SNSPDs) have been demonstrated to offer superior performance in detection efficiency, timing resolution, and count rates over semiconductor photodetectors, and are a suitable technology for high photon efficiency links. Recently photon detectors based on superconducting nanowires have become commercially available, and we have assessed the characteristics and performance of one such commercial system as a candidate for potential utilization in ground receiver designs. The SNSPD system features independent channels which can be added modularly, and we analyze the scalability of the system to support different data rates, as well as consider coupling concepts and issues as the number of channels increases.

Progress Towards High-Sensitivity Arrays of Detectors of Sub-mm Radiation Using Superconducting Tunnel Junctions with Integrated Radio Frequency Single-Electron Transistors

NASA Technical Reports Server (NTRS)

Stevenson, T. R.; Hsieh, W.-T.; Li, M. J.; Prober, D. E.; Rhee, K. W.; Schoelkopf, R. J.; Stahle, C. M.; Teufel, J.; Wollack, E. J.

2004-01-01

For high resolution imaging and spectroscopy in the FIR and submillimeter, space observatories will demand sensitive, fast, compact, low-power detector arrays with 104 pixels and sensitivity less than 10(exp -20) W/Hz(sup 0.5). Antenna-coupled superconducting tunnel junctions with integrated rf single-electron transistor readout amplifiers have the potential for achieving this high level of sensitivity, and can take advantage of an rf multiplexing technique. The device consists of an antenna to couple radiation into a small superconducting volume and cause quasiparticle excitations, and a single-electron transistor to measure current through junctions contacting the absorber. We describe optimization of device parameters, and results on fabrication techniques for producing devices with high yield for detector arrays. We also present modeling of expected saturation power levels, antenna coupling, and rf multiplexing schemes.

Quantum memristor in a superconducting circuit

NASA Astrophysics Data System (ADS)

Salmilehto, Juha; Sanz, Mikel; di Ventra, Massimiliano; Solano, Enrique

Memristors, resistive elements that retain information of their past, have garnered interest due to their paradigm-changing potential in information processing and electronics. The emergent hysteretic behaviour allows for novel architectural applications and has recently been classically demonstrated in a simplified superconducting setup using the phase-dependent conductance in the tunnel-junction-microscopic model. In this contribution, we present a truly quantum model for a memristor constructed using established elements and techniques in superconducting nanoelectronics, and explore the parameters for feasible operation as well as refine the methods for quantifying the memory retention. In particular, the memristive behaviour is shown to arise from quasiparticle-induced tunneling in the full dissipative model and can be observed in the phase-driven tunneling current. The relevant hysteretic behaviour should be observable using current state-of-the-art measurements for detecting quasiparticle excitations. Our theoretical findings constitute the first quantum memristor in a superconducting circuit and act as the starting point for designing further circuit elements that have non-Markovian characteristics The authors acknowledge support from the CCQED EU project and the Finnish Cultural Foundation.

Observing single quantum trajectories of a superconducting qubit: ensemble properties and driven dynamics

NASA Astrophysics Data System (ADS)

Weber, Steven; Murch, K. W.; Chantasri, A.; Dressel, J.; Jordan, A. N.; Siddiqi, I.

2014-03-01

We use weak measurements to track individual quantum trajectories of a superconducting qubit embedded in a microwave cavity. Using a near-quantum-limited parametric amplifier, we selectively measure either the phase or amplitude of the cavity field, and thereby confine trajectories to either the equator or a meridian of the Bloch sphere. We analyze ensembles of trajectories to determine statistical properties such as the most likely path and most likely time connecting pre and post-selected quantum states. We compare our results with theoretical predictions derived from an action principle for continuous quantum measurement. Furthermore, by introducing a qubit drive, we investigate the interplay between unitary state evolution and non-unitary measurement dynamics. This work was supported by the IARPA CSQ program and the ONR.

Tunable sub-gap radiation detection with superconducting resonators

NASA Astrophysics Data System (ADS)

Dupré, O.; Benoît, A.; Calvo, M.; Catalano, A.; Goupy, J.; Hoarau, C.; Klein, T.; Le Calvez, K.; Sacépé, B.; Monfardini, A.; Levy-Bertrand, F.

2017-04-01

We have fabricated planar amorphous indium oxide superconducting resonators ({T}{{c}}˜ 2.8 K) that are sensitive to frequency-selective radiation in the range of 7-10 GHz. Those values lay far below twice the superconducting gap that is worth about 200 GHz. The photon detection consists in a shift of the fundamental resonance frequency. We show that the detected frequency can be adjusted by modulating the total length of the superconducting resonator. We attribute those observations to the excitation of higher-order resonance modes. The coupling between the fundamental lumped and the higher order distributed resonance is due to the kinetic inductance nonlinearity with current. These devices, that we have called sub-gap kinetic inductance detectors, are to be distinguished from the standard kinetic inductance detectors in which quasi-particles are generated when incident light breaks down Cooper pairs.

Quantum interference in an interfacial superconductor.

PubMed

Goswami, Srijit; Mulazimoglu, Emre; Monteiro, Ana M R V L; Wölbing, Roman; Koelle, Dieter; Kleiner, Reinhold; Blanter, Ya M; Vandersypen, Lieven M K; Caviglia, Andrea D

2016-10-01

The two-dimensional superconductor that forms at the interface between the complex oxides lanthanum aluminate (LAO) and strontium titanate (STO) has several intriguing properties that set it apart from conventional superconductors. Most notably, an electric field can be used to tune its critical temperature (T c ; ref. 7), revealing a dome-shaped phase diagram reminiscent of high-T c superconductors. So far, experiments with oxide interfaces have measured quantities that probe only the magnitude of the superconducting order parameter and are not sensitive to its phase. Here, we perform phase-sensitive measurements by realizing the first superconducting quantum interference devices (SQUIDs) at the LAO/STO interface. Furthermore, we develop a new paradigm for the creation of superconducting circuit elements, where local gates enable the in situ creation and control of Josephson junctions. These gate-defined SQUIDs are unique in that the entire device is made from a single superconductor with purely electrostatic interfaces between the superconducting reservoir and the weak link. We complement our experiments with numerical simulations and show that the low superfluid density of this interfacial superconductor results in a large, gate-controllable kinetic inductance of the SQUID. Our observation of robust quantum interference opens up a new pathway to understanding the nature of superconductivity at oxide interfaces.

Superconducting Qubit with Integrated Single Flux Quantum Controller Part II: Experimental Characterization

NASA Astrophysics Data System (ADS)

Leonard, Edward, Jr.; Beck, Matthew; Thorbeck, Ted; Zhu, Shaojiang; Howington, Caleb; Nelson, Jj; Plourde, Britton; McDermott, Robert

We describe the characterization of a single flux quantum (SFQ) pulse generator cofabricated with a superconducting quantum circuit on a single chip. Resonant trains of SFQ pulses are used to induce coherent qubit rotations on the Bloch sphere. We describe the SFQ drive characteristics of the qubit at the fundamental transition frequency and at subharmonics (ω01 / n , n = 2 , 3 , 4 , ⋯). We address the issue of quasiparticle poisoning due to the proximal SFQ pulse generator, and we characterize the fidelity of SFQ-based rotations using randomized benchmarking. Present address: IBM T.J. Watson Research Center.

Observation of entanglement between itinerant microwave photons and a superconducting qubit.

PubMed

Eichler, C; Lang, C; Fink, J M; Govenius, J; Filipp, S; Wallraff, A

2012-12-14

A localized qubit entangled with a propagating quantum field is well suited to study nonlocal aspects of quantum mechanics and may also provide a channel to communicate between spatially separated nodes in a quantum network. Here, we report the on-demand generation and characterization of Bell-type entangled states between a superconducting qubit and propagating microwave fields composed of zero-, one-, and two-photon Fock states. Using low noise linear amplification and efficient data acquisition we extract all relevant correlations between the qubit and the photon states and demonstrate entanglement with high fidelity.

A 64-pixel NbTiN superconducting nanowire single-photon detector array for spatially resolved photon detection.

PubMed

Miki, Shigehito; Yamashita, Taro; Wang, Zhen; Terai, Hirotaka

2014-04-07

We present the characterization of two-dimensionally arranged 64-pixel NbTiN superconducting nanowire single-photon detector (SSPD) array for spatially resolved photon detection. NbTiN films deposited on thermally oxidized Si substrates enabled the high-yield production of high-quality SSPD pixels, and all 64 SSPD pixels showed uniform superconducting characteristics within the small range of 7.19-7.23 K of superconducting transition temperature and 15.8-17.8 μA of superconducting switching current. Furthermore, all of the pixels showed single-photon sensitivity, and 60 of the 64 pixels showed a pulse generation probability higher than 90% after photon absorption. As a result of light irradiation from the single-mode optical fiber at different distances between the fiber tip and the active area, the variations of system detection efficiency (SDE) in each pixel showed reasonable Gaussian distribution to represent the spatial distributions of photon flux intensity.

Superconducting thermal neutron detectors

NASA Astrophysics Data System (ADS)

Merlo, V.; Pietropaolo, A.; Celentano, G.; Cirillo, M.; Lucci, M.; Ottaviani, I.; Salvato, M.; Scherillo, A.; Schooneveld, E. M.; Vannozzi, A.

2016-09-01

A neutron detection concept is presented that is based on superconductive niobium nitride (NbN) strips coated by a boron (B) layer. The working principle is well described by a hot spot mechanism: upon the occurrence of the nuclear reactions n + 10B → α + 7Li + 2.8 MeV, the energy released by the secondary particles into the strip induces a superconducting-normal state transition. The latter is recognized as a voltage signal which is the evidence of the incident neutron. The above described detection principle has been experimentally assessed and verified by irradiating the samples with a pulsed neutron beam at the ISIS spallation neutron source (UK). It is found that the boron coated superconducting strips, kept at a temperature T below 11K and current-biased below the critical current IC, are driven into the normal state upon thermal neutron irradiation. Measurements on the counting rate of the device are presented and the basic physical features of the detector are discussed and compared to those of a borated Nb superconducting strip.

The Quantum Socket: Wiring for Superconducting Qubits - Part 1

NASA Astrophysics Data System (ADS)

McConkey, T. G.; Bejanin, J. H.; Rinehart, J. R.; Bateman, J. D.; Earnest, C. T.; McRae, C. H.; Rohanizadegan, Y.; Shiri, D.; Mariantoni, M.; Penava, B.; Breul, P.; Royak, S.; Zapatka, M.; Fowler, A. G.

Quantum systems with ten superconducting quantum bits (qubits) have been realized, making it possible to show basic quantum error correction (QEC) algorithms. However, a truly scalable architecture has not been developed yet. QEC requires a two-dimensional array of qubits, restricting any interconnection to external classical systems to the third axis. In this talk, we introduce an interconnect solution for solid-state qubits: The quantum socket. The quantum socket employs three-dimensional wires and makes it possible to connect classical electronics with quantum circuits more densely and accurately than methods based on wire bonding. The three-dimensional wires are based on spring-loaded pins engineered to insure compatibility with quantum computing applications. Extensive design work and machining was required, with focus on material quality to prevent magnetic impurities. Microwave simulations were undertaken to optimize the design, focusing on the interface between the micro-connector and an on-chip coplanar waveguide pad. Simulations revealed good performance from DC to 10 GHz and were later confirmed against experimental measurements.

Implementing universal nonadiabatic holonomic quantum gates with transmons

NASA Astrophysics Data System (ADS)

Hong, Zhuo-Ping; Liu, Bao-Jie; Cai, Jia-Qi; Zhang, Xin-Ding; Hu, Yong; Wang, Z. D.; Xue, Zheng-Yuan

2018-02-01

Geometric phases are well known to be noise resilient in quantum evolutions and operations. Holonomic quantum gates provide us with a robust way towards universal quantum computation, as these quantum gates are actually induced by non-Abelian geometric phases. Here we propose and elaborate how to efficiently implement universal nonadiabatic holonomic quantum gates on simpler superconducting circuits, with a single transmon serving as a qubit. In our proposal, an arbitrary single-qubit holonomic gate can be realized in a single-loop scenario by varying the amplitudes and phase difference of two microwave fields resonantly coupled to a transmon, while nontrivial two-qubit holonomic gates may be generated with a transmission-line resonator being simultaneously coupled to the two target transmons in an effective resonant way. Moreover, our scenario may readily be scaled up to a two-dimensional lattice configuration, which is able to support large scalable quantum computation, paving the way for practically implementing universal nonadiabatic holonomic quantum computation with superconducting circuits.

TES development for a frequency selective bolometer camera.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datesman, A. M.; Downes, T. P.; Perera, T. A.

2009-06-01

We discuss the development, at Argonne National Laboratory (ANL), of a four-pixel camera with four spectral channels centered at 150, 220, 270, and 360 GHz. The scientific motivation involves photometry of distant dusty galaxies located by Spitzer and SCUBA, as well as the study of other millimeter-wave sources such as ultra-luminous infrared galaxies, the Sunyaev-Zeldovich effect in clusters, and galactic dust. The camera incorporates Frequency Selective Bolometer (FSB) and superconducting Transition-Edge Sensor (TES) technology. The current generation of TES devices we examine utilizes proximity effect superconducting bilayers of Mo/Au, Ti, or Ti/Au as TESs, located along with frequency selective absorbingmore » structures on silicon nitride membranes. The detector incorporates lithographically patterned structures designed to address both TES device stability and detector thermal transport concerns. The membrane is not perforated, resulting in a detector which is comparatively robust mechanically. In this paper, we report on the development of the superconducting bilayer TES technology, the design and testing of the detector thermal transport and device stability control structures, optical and thermal test results, and the use of new materials.« less

Fabrication of Compact Superconducting Lowpass Filters for Ultrasensitive Detectors

NASA Technical Reports Server (NTRS)

Brown, Ari; Chervenak, James; Chuss, David; Mikula, Vilem; Ray, Christopher; Rostem, Karwan; U-Yen, Kongpop; Wassell, Edward; Wollack, Edward

2012-01-01

It is extremely important for current and future far-infrared and sub-millimeter ultrasensitive detectors, which include transition edge sensors (TES) and microwave kinetic inductance detectors, to be adequately filtered from stray electromagnetic radiation in order to achieve their optimal performance. One means of filtering stray radiation is to block leakage associated with electrical connections in the detector environment. Here we discuss a fabrication methodology for realizing non-dissipative planar filters imbedded in the wall of the detector enclosure to limit wave propagation modes up to far-infrared frequencies. Our methodology consists of fabricating a boxed stripline transmission line, in which a superconducting (Nb, Mo, or Al) transmission line is encased in a silicon dioxide dielectric insulator coated with a metallic shell. We report on achieved attenuation and return loss and find that it replicates the simulated data to a high degree.

High-fidelity gates towards a scalable superconducting quantum processor

NASA Astrophysics Data System (ADS)

Chow, Jerry M.; Corcoles, Antonio D.; Gambetta, Jay M.; Rigetti, Chad; Johnson, Blake R.; Smolin, John A.; Merkel, Seth; Poletto, Stefano; Rozen, Jim; Rothwell, Mary Beth; Keefe, George A.; Ketchen, Mark B.; Steffen, Matthias

2012-02-01

We experimentally explore the implementation of high-fidelity gates on multiple superconducting qubits coupled to multiple resonators. Having demonstrated all-microwave single and two qubit gates with fidelities > 90% on multi-qubit single-resonator systems, we expand the application to qubits across two resonators and investigate qubit coupling in this circuit. The coupled qubit-resonators are building blocks towards two-dimensional lattice networks for the application of surface code quantum error correction algorithms.

Local tuning of the order parameter in superconducting weak links: A zero-inductance nanodevice

NASA Astrophysics Data System (ADS)

Winik, Roni; Holzman, Itamar; Dalla Torre, Emanuele G.; Buks, Eyal; Ivry, Yachin

2018-03-01

Controlling both the amplitude and the phase of the superconducting quantum order parameter (" separators="|ψ ) in nanostructures is important for next-generation information and communication technologies. The lack of electric resistance in superconductors, which may be advantageous for some technologies, hinders convenient voltage-bias tuning and hence limits the tunability of ψ at the microscopic scale. Here, we demonstrate the local tunability of the phase and amplitude of ψ, obtained by patterning with a single lithography step a Nb nano-superconducting quantum interference device (nano-SQUID) that is biased at its nanobridges. We accompany our experimental results by a semi-classical linearized model that is valid for generic nano-SQUIDs with multiple ports and helps simplify the modelling of non-linear couplings among the Josephson junctions. Our design helped us reveal unusual electric characteristics with effective zero inductance, which is promising for nanoscale magnetic sensing and quantum technologies.

Characterization and Analysis of a Multicolor Quantum Well Infrared Photodetector

DTIC Science & Technology

2006-06-01

and characterization of performance of a newly designed, multicolor quantum well infrared photodetector ( QWIP ). Specifically, it focuses on a detector...quantum well infrared detectors makes them suitable for use in the field. 15. NUMBER OF PAGES 67 14. SUBJECT TERMS Quantum Well, QWIP , Three...characterization of performance of a newly designed, multicolor quantum well infrared photodetector ( QWIP ). Specifically, it focuses on a detector

Failure Scenarios and Mitigations for the BABAR Superconducting Solenoid

NASA Astrophysics Data System (ADS)

Thompson, EunJoo; Candia, A.; Craddock, W. W.; Racine, M.; Weisend, J. G.

2006-04-01

The cryogenic department at the Stanford Linear Accelerator Center is responsible for the operation, troubleshooting, and upgrade of the 1.5 Tesla superconducting solenoid detector for the BABAR B-factory experiment. Events that disable the detector are rare but significantly impact the availability of the detector for physics research. As a result, a number of systems and procedures have been developed over time to minimize the downtime of the detector, for example improved control systems, improved and automatic backup systems, and spares for all major components. Together they can prevent or mitigate many of the failures experienced by the utilities, mechanical systems, controls and instrumentation. In this paper we describe various failure scenarios, their effect on the detector, and the modifications made to mitigate the effects of the failure. As a result of these modifications the reliability of the detector has increased significantly with only 3 shutdowns of the detector due to cryogenics systems over the last 2 years.

Principle and experimental investigation of current-driven negative-inductance superconducting quantum interference device

NASA Astrophysics Data System (ADS)

Li, Hao; Liu, Jianshe; Zhang, Yingshan; Cai, Han; Li, Gang; Liu, Qichun; Han, Siyuan; Chen, Wei

2017-03-01

A negative-inductance superconducting quantum interference device (nSQUID) is an adiabatic superconducting logic device with high energy efficiency, and therefore a promising building block for large-scale low-power superconducting computing. However, the principle of the nSQUID is not that straightforward and an nSQUID driven by voltage is vulnerable to common mode noise. We investigate a single nSQUID driven by current instead of voltage, and clarify the principle of the adiabatic transition of the current-driven nSQUID between different states. The basic logic operations of the current-driven nSQUID with proper parameters are simulated by WRspice. The corresponding circuit is fabricated with a 100 A cm-2 Nb-based lift-off process, and the experimental results at low temperature confirm the basic logic operations as a gated buffer.

Quantum technologies with hybrid systems

PubMed Central

Kurizki, Gershon; Bertet, Patrice; Kubo, Yuimaru; Mølmer, Klaus; Petrosyan, David; Rabl, Peter; Schmiedmayer, Jörg

2015-01-01

An extensively pursued current direction of research in physics aims at the development of practical technologies that exploit the effects of quantum mechanics. As part of this ongoing effort, devices for quantum information processing, secure communication, and high-precision sensing are being implemented with diverse systems, ranging from photons, atoms, and spins to mesoscopic superconducting and nanomechanical structures. Their physical properties make some of these systems better suited than others for specific tasks; thus, photons are well suited for transmitting quantum information, weakly interacting spins can serve as long-lived quantum memories, and superconducting elements can rapidly process information encoded in their quantum states. A central goal of the envisaged quantum technologies is to develop devices that can simultaneously perform several of these tasks, namely, reliably store, process, and transmit quantum information. Hybrid quantum systems composed of different physical components with complementary functionalities may provide precisely such multitasking capabilities. This article reviews some of the driving theoretical ideas and first experimental realizations of hybrid quantum systems and the opportunities and challenges they present and offers a glance at the near- and long-term perspectives of this fascinating and rapidly expanding field. PMID:25737558

Quantum technologies with hybrid systems.

PubMed

Kurizki, Gershon; Bertet, Patrice; Kubo, Yuimaru; Mølmer, Klaus; Petrosyan, David; Rabl, Peter; Schmiedmayer, Jörg

2015-03-31

An extensively pursued current direction of research in physics aims at the development of practical technologies that exploit the effects of quantum mechanics. As part of this ongoing effort, devices for quantum information processing, secure communication, and high-precision sensing are being implemented with diverse systems, ranging from photons, atoms, and spins to mesoscopic superconducting and nanomechanical structures. Their physical properties make some of these systems better suited than others for specific tasks; thus, photons are well suited for transmitting quantum information, weakly interacting spins can serve as long-lived quantum memories, and superconducting elements can rapidly process information encoded in their quantum states. A central goal of the envisaged quantum technologies is to develop devices that can simultaneously perform several of these tasks, namely, reliably store, process, and transmit quantum information. Hybrid quantum systems composed of different physical components with complementary functionalities may provide precisely such multitasking capabilities. This article reviews some of the driving theoretical ideas and first experimental realizations of hybrid quantum systems and the opportunities and challenges they present and offers a glance at the near- and long-term perspectives of this fascinating and rapidly expanding field.

Quantum technologies with hybrid systems

NASA Astrophysics Data System (ADS)

Kurizki, Gershon; Bertet, Patrice; Kubo, Yuimaru; Mølmer, Klaus; Petrosyan, David; Rabl, Peter; Schmiedmayer, Jörg

2015-03-01

An extensively pursued current direction of research in physics aims at the development of practical technologies that exploit the effects of quantum mechanics. As part of this ongoing effort, devices for quantum information processing, secure communication, and high-precision sensing are being implemented with diverse systems, ranging from photons, atoms, and spins to mesoscopic superconducting and nanomechanical structures. Their physical properties make some of these systems better suited than others for specific tasks; thus, photons are well suited for transmitting quantum information, weakly interacting spins can serve as long-lived quantum memories, and superconducting elements can rapidly process information encoded in their quantum states. A central goal of the envisaged quantum technologies is to develop devices that can simultaneously perform several of these tasks, namely, reliably store, process, and transmit quantum information. Hybrid quantum systems composed of different physical components with complementary functionalities may provide precisely such multitasking capabilities. This article reviews some of the driving theoretical ideas and first experimental realizations of hybrid quantum systems and the opportunities and challenges they present and offers a glance at the near- and long-term perspectives of this fascinating and rapidly expanding field.

Circuit quantum acoustodynamics with surface acoustic waves.

PubMed

Manenti, Riccardo; Kockum, Anton F; Patterson, Andrew; Behrle, Tanja; Rahamim, Joseph; Tancredi, Giovanna; Nori, Franco; Leek, Peter J

2017-10-17

The experimental investigation of quantum devices incorporating mechanical resonators has opened up new frontiers in the study of quantum mechanics at a macroscopic level. It has recently been shown that surface acoustic waves (SAWs) can be piezoelectrically coupled to superconducting qubits, and confined in high-quality Fabry-Perot cavities in the quantum regime. Here we present measurements of a device in which a superconducting qubit is coupled to a SAW cavity, realising a surface acoustic version of cavity quantum electrodynamics. We use measurements of the AC Stark shift between the two systems to determine the coupling strength, which is in agreement with a theoretical model. This quantum acoustodynamics architecture may be used to develop new quantum acoustic devices in which quantum information is stored in trapped on-chip acoustic wavepackets, and manipulated in ways that are impossible with purely electromagnetic signals, due to the 10 5 times slower mechanical waves.In this work, Manenti et al. present measurements of a device in which a tuneable transmon qubit is piezoelectrically coupled to a surface acoustic wave cavity, realising circuit quantum acoustodynamic architecture. This may be used to develop new quantum acoustic devices.

Weak Measurement and Quantum Smoothing of a Superconducting Qubit

NASA Astrophysics Data System (ADS)

Tan, Dian

In quantum mechanics, the measurement outcome of an observable in a quantum system is intrinsically random, yielding a probability distribution. The state of the quantum system can be described by a density matrix rho(t), which depends on the information accumulated until time t, and represents our knowledge about the system. The density matrix rho(t) gives probabilities for the outcomes of measurements at time t. Further probing of the quantum system allows us to refine our prediction in hindsight. In this thesis, we experimentally examine a quantum smoothing theory in a superconducting qubit by introducing an auxiliary matrix E(t) which is conditioned on information obtained from time t to a final time T. With the complete information before and after time t, the pair of matrices [rho(t), E(t)] can be used to make smoothed predictions for the measurement outcome at time t. We apply the quantum smoothing theory in the case of continuous weak measurement unveiling the retrodicted quantum trajectories and weak values. In the case of strong projective measurement, while the density matrix rho(t) with only diagonal elements in a given basis |n〉 may be treated as a classical mixture, we demonstrate a failure of this classical mixture description in determining the smoothed probabilities for the measurement outcome at time t with both diagonal rho(t) and diagonal E(t). We study the correlations between quantum states and weak measurement signals and examine aspects of the time symmetry of continuous quantum measurement. We also extend our study of quantum smoothing theory to the case of resonance fluorescence of a superconducting qubit with homodyne measurement and observe some interesting effects such as the modification of the excited state probabilities, weak values, and evolution of the predicted and retrodicted trajectories.

Radiation detector using a bulk high T.sub.c superconductor

DOEpatents

Artuso, Joseph F.; Franks, Larry A.; Hull, Kenneth L.; Symko, Orest G.

1993-01-01

A radiation detector (10) is provided, wherein a bulk high T.sub.c superconducting sample (11) is placed in a magnetic field and maintained at a superconducting temperature. Photons of incident radiation will cause localized heating in superconducting loops of the sample destroying trapped flux and redistributing the fluxons, and reducing the critical current of the loops. Subsequent cooling of the sample in the magnetic field will cause trapped flux redistributed Abrikosov fluxons and trapped Josephson fluxons. The destruction and trapping of the fluxons causes changes in the magnetization of the sample inducing currents in opposite directions in a pickup coil (12) which is coupled by an input coil (15) to an rf SQUID (16).

Radiation detector using a bulk high T[sub c] superconductor

DOEpatents

Artuso, J.F.; Franks, L.A.; Hull, K.L.; Symko, O.G.

1993-12-07

A radiation detector is provided, wherein a bulk high T[sub c] superconducting sample is placed in a magnetic field and maintained at a superconducting temperature. Photons of incident radiation will cause localized heating in superconducting loops of the sample destroying trapped flux and redistributing the fluxons, and reducing the critical current of the loops. Subsequent cooling of the sample in the magnetic field will cause trapped flux redistributed Abrikosov fluxons and trapped Josephson fluxons. The destruction and trapping of the fluxons causes changes in the magnetization of the sample inducing currents in opposite directions in a pickup coil which is coupled by an input coil to an rf SQUID. 4 figures.

Absence of Local Fluctuating Dimers in Superconducting Ir 1-x(Pt,Rh) xTe 2

DOE PAGES

Yu, Runze; Banerjee, S.; Lei, H. C.; ...

2018-06-01

The compound IrTe2 is known to exhibit a transition to a modulated state featuring Ir-Ir dimers, with large associated atomic displacements. Partial substitution of Pt or Rh for Ir destabilizes the modulated structure and induces superconductivity. It has been proposed that quantum critical dimer fluctuations might be associated with the superconductivity. Here we test for such local dimer correlations and demonstrate their absence. X-ray pair distribution function approach reveals that the local structure of Ir 0.95Pt 0.05Te 2 and Ir 0.8Rh 0.2Te 2 dichalcogenide superconductors with compositions just past the dimer/superconductor boundary is explained well by a dimer-free model downmore » to 10 K, ruling out the possibility of there being nanoscale dimer fluctuations in this regime. This is inconsistent with the proposed quantum-critical-point-like interplay of the dimer state and superconductivity, and precludes scenarios for dimer fluctuations mediated superconducting pairing.« less

Absence of Local Fluctuating Dimers in Superconducting Ir 1-x(Pt,Rh) xTe 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Runze; Banerjee, S.; Lei, H. C.

The compound IrTe2 is known to exhibit a transition to a modulated state featuring Ir-Ir dimers, with large associated atomic displacements. Partial substitution of Pt or Rh for Ir destabilizes the modulated structure and induces superconductivity. It has been proposed that quantum critical dimer fluctuations might be associated with the superconductivity. Here we test for such local dimer correlations and demonstrate their absence. X-ray pair distribution function approach reveals that the local structure of Ir 0.95Pt 0.05Te 2 and Ir 0.8Rh 0.2Te 2 dichalcogenide superconductors with compositions just past the dimer/superconductor boundary is explained well by a dimer-free model downmore » to 10 K, ruling out the possibility of there being nanoscale dimer fluctuations in this regime. This is inconsistent with the proposed quantum-critical-point-like interplay of the dimer state and superconductivity, and precludes scenarios for dimer fluctuations mediated superconducting pairing.« less

Chiral superconductors.

PubMed

Kallin, Catherine; Berlinsky, John

2016-05-01

Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from μSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed.

Absence of local fluctuating dimers in superconducting Ir1 -x(Pt,Rh ) xTe2

NASA Astrophysics Data System (ADS)

Yu, Runze; Banerjee, S.; Lei, H. C.; Sinclair, Ryan; Abeykoon, M.; Zhou, H. D.; Petrovic, C.; Guguchia, Z.; Bozin, E. S.

2018-05-01

The compound IrTe2 is known to exhibit a transition to a modulated state featuring Ir-Ir dimers, with large associated atomic displacements. Partial substitution of Pt or Rh for Ir destabilizes the modulated structure and induces superconductivity. It has been proposed that quantum critical dimer fluctuations might be associated with the superconductivity. Here we test for such local dimer correlations and demonstrate their absence. X-ray pair distribution function approach reveals that the local structure of Ir0 :95Pt0 :05Te2 and Ir0 :8Rh0 :2Te2 dichalcogenide superconductors with compositions just past the dimer/superconductor boundary is explained well by a dimer-free model down to 10 K, ruling out the possibility of there being nanoscale dimer fluctuations in this regime. This is inconsistent with the proposed quantum-critical-point-like interplay of the dimer state and superconductivity, and precludes scenarios for dimer fluctuations mediated superconducting pairing.

Observation of quantum jumps in a superconducting quantum bit

NASA Astrophysics Data System (ADS)

Vijay, R.

2011-03-01

Superconducting qubit technology has made great advances since the first demonstration of coherent oscillations more than 10 years ago. Coherence times have improved by several orders of magnitude and significant progress has been made in qubit state readout fidelity. However, a fast, high-fidelity, quantum non-demolition measurement scheme which is essential to implement quantum error correction has so far been missing. We demonstrate such a scheme for the first time where we continuously measure the state of a superconducting quantum bit using a fast, ultralow-noise parametric amplifier. This arrangement allows us to observe quantum jumps between the qubit states in real time. The key development enabling this experiment is the use of a low quality factor (Q), nonlinear resonator to implement a phase-sensitive parametric amplifier operating near the quantum limit. The nonlinear resonator was constructed using a two junction SQUID shunted with an on-chip capacitor. The SQUID allowed us to tune the operating band of the amplifier and the low Q provided us with a bandwidth greater than 10 MHz, sufficient to observe jumps in the qubit state in real time. I will briefly describe the operation of the parametric amplifier and discuss how it was used to measure the state of a transmon qubit in the circuit QED architecture. I will discuss measurement fidelity and the statistics of the quantum jumps. I will conclude by discussing the implications of this development for quantum information processing and further improvements to the measurement technique. We acknowledge support from AFOSR and the Hertz Foundation.

Displacemon Electromechanics: How to Detect Quantum Interference in a Nanomechanical Resonator

NASA Astrophysics Data System (ADS)

Khosla, K. E.; Vanner, M. R.; Ares, N.; Laird, E. A.

2018-04-01

We introduce the "displacemon" electromechanical architecture that comprises a vibrating nanobeam, e.g., a carbon nanotube, flux coupled to a superconducting qubit. This platform can achieve strong and even ultrastrong coupling, enabling a variety of quantum protocols. We use this system to describe a protocol for generating and measuring quantum interference between trajectories of a nanomechanical resonator. The scheme uses a sequence of qubit manipulations and measurements to cool the resonator, to apply two effective diffraction gratings, and then to measure the resulting interference pattern. We demonstrate the feasibility of generating a spatially distinct quantum superposition state of motion containing more than 1 06 nucleons using a vibrating nanotube acting as a junction in this new superconducting qubit configuration.

Cross-Talk in Superconducting Transmon Quantum Computing Architecture

NASA Astrophysics Data System (ADS)

Abraham, David; Chow, Jerry; Corcoles, Antonio; Rothwell, Mary; Keefe, George; Gambetta, Jay; Steffen, Matthias; IBM Quantum Computing Team

2013-03-01

Superconducting transmon quantum computing test structures often exhibit significant undesired cross-talk. For experiments with only a handful of qubits this cross-talk can be quantified and understood, and therefore corrected. As quantum computing circuits become more complex, and thereby contain increasing numbers of qubits and resonators, it becomes more vital that the inadvertent coupling between these elements is minimized. The task of accurately controlling each single qubit to the level of precision required throughout the realization of a quantum algorithm is difficult by itself, but coupled with the need of nulling out leakage signals from neighboring qubits or resonators would quickly become impossible. We discuss an approach to solve this critical problem. We acknowledge support from IARPA under contract W911NF-10-1-0324.

Spin dynamics near a putative antiferromagnetic quantum critical point in Cu-substituted BaFe 2 As 2 and its relation to high-temperature superconductivity

DOE PAGES

Kim, M. G.; Wang, M.; Tucker, G. S.; ...

2015-12-02

We present the results of elastic and inelastic neutron scattering measurements on nonsuperconducting Ba(Fe 0.957Cu 0.043) 2As 2, a composition close to a quantum critical point between antiferromagnetic (AFM) ordered and paramagnetic phases. By comparing these results with the spin fluctuations in the low-Cu composition as well as the parent compound BaFe 2As 2 and superconducting Ba(Fe 1–xNi x) 2As 2 compounds, we demonstrate that paramagnon-like spin fluctuations are evident in the antiferromagnetically ordered state of Ba(Fe 0.957Cu 0.043) 2As 2, which is distinct from the AFM-like spin fluctuations in the superconducting compounds. Our observations suggest that Cu substitution decouplesmore » the interaction between quasiparticles and the spin fluctuations. In addition, we show that the spin-spin correlation length ξ(T) increases rapidly as the temperature is lowered and find ω/T scaling behavior, the hallmark of quantum criticality, at an antiferromagnetic quantum critical point.« less

Magnetism in Na-filled Fe-based skutterudites

DOE PAGES

Xing, Guangzong; Fan, Xiaofeng; Zheng, Weitao; ...

2015-06-01

The interplay of superconductivity and magnetism is a subject of ongoing interest, stimulated most recently by the discovery of Fe-based superconductivity and the recognition that spin-fluctuations near a magnetic quantum critical point may provide an explanation for the superconductivity and the order parameter. We investigate magnetism in the Na filled Fe-based skutterudites using first principles calculations. NaFe 4Sb 12 is a known ferromagnet near a quantum critical point. We find a ferromagnetic metallic state for this compound driven by a Stoner type instability, consistent with prior work. In accord with prior work, the magnetization is overestimated, as expected for amore » material near an itinerant ferromagnetic quantum critical point. NaFe 4P 12 also shows a ferromagnetic instability at the density functional level, but this instability is much weaker than that of NaFe 4Sb 12, possibly placing it on the paramagnetic side of the quantum critical point. NaFe 4As 12 shows intermediate behavior. We also present results for skutterudite FeSb 3, which is a metastable phase that has been reported in thin film form.« less

Detection of long wavelength infrared at moderate temperatures

NASA Technical Reports Server (NTRS)

Tredwell, T. J.

1977-01-01

Technical approaches for the advanced development of 8-12 micrometer detectors operating at elevated temperatures were defined. The theoretical limits to performance of 8-12 micrometer quantum detectors (photoconductive and photovoltaic) and thermal detectors (pyroelectrics, bolometers etc). An analytic model of signal and noise in both quantum detectors and pyroelectric detectors was developed and candidate materials for both detector types were identified and examined. The present status of both quantum and thermal detectors was assessed as well as the parameters limiting operating temperature and detectivity. The areas of research and development likely to lead to detector performance near the theoretical limit are identified.

Emergent functions of quantum materials

NASA Astrophysics Data System (ADS)

Tokura, Yoshinori; Kawasaki, Masashi; Nagaosa, Naoto

2017-11-01

Materials can harbour quantum many-body systems, most typically in the form of strongly correlated electrons in solids, that lead to novel and remarkable functions thanks to emergence--collective behaviours that arise from strong interactions among the elements. These include the Mott transition, high-temperature superconductivity, topological superconductivity, colossal magnetoresistance, giant magnetoelectric effect, and topological insulators. These phenomena will probably be crucial for developing the next-generation quantum technologies that will meet the urgent technological demands for achieving a sustainable and safe society. Dissipationless electronics using topological currents and quantum spins, energy harvesting such as photovoltaics and thermoelectrics, and secure quantum computing and communication are the three major fields of applications working towards this goal. Here, we review the basic principles and the current status of the emergent phenomena and functions in materials from the viewpoint of strong correlation and topology.

First Tests of Prototype SCUBA-2 Superconducting Bolometer Array

NASA Astrophysics Data System (ADS)

Woodcraft, Adam L.; Ade, Peter A. R.; Bintley, Dan; Hunt, Cynthia L.; Sudiwala, Rashmi V.; Hilton, Gene C.; Irwin, Kent D.; Reintsema, Carl D.; Audley, Michael D.; Holland, Wayne S.; MacIntosh, Mike

2006-09-01

We present results of the first tests on a 1280 pixel superconducting bolometer array, a prototype for SCUBA-2, a sub-mm camera being built for the James Clerk Maxwell Telescope in Hawaii. The bolometers are TES (transition edge sensor) detectors; these take advantage of the large variation of resistance with temperature through the superconducting transition. To keep the number of wires reasonable, a multiplexed read-out is used. Each pixel is read out through an individual DC SQUID; room temperature electronics switch between rows in the array by biasing the appropriate SQUIDs in turn. Arrays of 100 SQUIDs in series for each column then amplify the output. Unlike previous TES arrays, the multiplexing elements are located beneath each pixel, making large arrays possible, but construction more challenging. The detectors are constructed from Mo/Cu bi-layers; this technique enables the transition temperature to be tuned using the proximity effect by choosing the thickness of the normal and superconducting materials. To achieve the required performance, the detectors are operated at a temperature of approximately 120 mK. We describe the results of a basic characterisation of the array, demonstrating that it is fully operational, and give the results of signal to noise measurements.

High Tc superconducting bolometric and nonbolometric infrared (IR) detectors

NASA Technical Reports Server (NTRS)

Lakeou, Samuel

1994-01-01

The original workplan for the first year of the project includes the following: establishment of a pilot superconductivity application laboratory at UDC to support the research component of the project; research on the source of electrical noise in High Tc superconducting films in order to optimize the film microstructure and lower the NEP; and lay the foundation of an academic support for exposing UDC students to the theory and application of High Tc superconductivity. Attached to this status report are abstracts and the course description for Introduction to Applications of Superconductivity.

Fabrication and Evaluation of Superconducting and Semiconducting Materials

DTIC Science & Technology

1993-09-01

Laboratory Material Physics Branch by conducting investigations into the properties of superconducting , magnetic , and other solid state materials. Studies...Physics Branch in conducting research into applied problems such as the design of magnetic shielding and superconducting quantum interference device...SQUID) magnetometry detection of magnetic anomalies. SFA provided research assistance in the areas of bulk ceramic sample preparation. conversion

RF Control and Measurement of Superconducting Qubits

DTIC Science & Technology

2015-02-14

Schoelkopf, Leonid I. Glazman, Michel H. Devoret. Coherent suppression of electromagnetic dissipation due to superconducting quasiparticles ...Frunzio, L.?I. Glazman, M.?H. Devoret. Non-Poissonian Quantum Jumps of a Fluxonium Qubit due to Quasiparticle Excitations, Physical Review Letters...Devoret, G. Catelani, L. I. Glazman, R. J. Schoelkopf. Measurement and control of quasiparticle dynamics in a superconducting qubit, Nature

Realizing Controllable Quantum States

NASA Astrophysics Data System (ADS)

Takayanagi, Hideaki; Nitta, Junsaku

1. Entanglement in solid states. Orbital entanglement and violation of bell inequalities in mesoscopic conductors / M. Büttiker, P. Samuelsson and E. V. Sukhoruk. Teleportation of electron spins with normal and superconducting dots / O. Sauret, D. Feinberg and T. Martin. Entangled state analysis for one-dimensional quantum spin system: singularity at critical point / A. Kawaguchi and K. Shimizu. Detecting crossed Andreev reflection by cross-current correlations / G. Bignon et al. Current correlations and transmission probabilities for a Y-shaped diffusive conductor / S. K. Yip -- 2. Mesoscopic electronics. Quantum bistability, structural transformation, and spontaneous persistent currents in mesoscopic Aharonov-Bohm loops / I. O. Kulik. Many-body effects on tunneling of electrons in magnetic-field-induced quasi one-dimensional systems in quantum wells / T. Kubo and Y. Tokura. Electron transport in 2DEG narrow channel under gradient magnetic field / M. Hara et al. Transport properties of a quantum wire with a side-coupled quantum dot / M. Yamaguchi et al. Photoconductivity- and magneto-transport studies of single InAs quantum wires / A. Wirthmann et al. Thermoelectric transports in charge-density-wave systems / H. Yoshimoto and S. Kurihara -- 3. Mesoscopic superconductivity. Parity-restricted persistent currents in SNS nanorings / A. D. Zaikin and S. V. Sharov. Large energy dependence of current noise in superconductingh/normal metal junctions / F. Pistolesi and M. Houzet. Generation of photon number states and their superpositions using a superconducting qubit in a microcavity / Yu-Xi Liu, L. F. Wei and F. Nori. Andreev interferometry for pumped currents / F. Taddei, M. Governale and R. Fazio. Suppression of Cooper-pair breaking against high magnetic fields in carbon nanotubes / J. Haruyama et al. Impact of the transport supercurrent on the Josephson effect / S. N. Shevchenko. Josephson current through spin-polarized Luttinger liquid / N. Yokoshi and S. Kurihara -- 4. Mesoscopic superconductivity with unconventional superconductor or ferromagnet. Ultraefficient microrefrigerators realized with ferromagnet-superconductor junctions / F. Giazotto et al. Anomalous charge transport in triplet superconductor junctions by the synergy effect of the proximity effect and the mid gap Andreev resonant states / Y. Tanaka and S. Kashiwaya. Paramagnetic and glass states in superconductive YBa[symbol]Cu[symbol]O[symbol] ceramics of sub-micron scale grains / H. Deguchi et al. Quantum properties of single-domain triplet superconductors / A. M. Gulian and K. S. Wood. A numerical study of Josephson current in p wave superconducting junctions / Y. Asano et al. Tilted bi-crystal sapphire substrates improve properties of grain boundary YBa[symbol]Cu[symbol]O[symbol] junctions and extend their Josephson response to THZ frequencies / E. Stepantsov et al. Circuit theory analysis of AB-plane tunnel junctions of unconventional superconductor Bi[symbol]Sr[symbol]Ca[symbol]Cu[symbol]O[symbol] / I. Shigeta et al. Transport properties of normal metal/anisotropic superconductor junctions in the eutectic system Sr[symbol]RuO[symbol]Ru / M. Kawamura et al. Macroscopic quantum tunneling in d-wave superconductor Josephson / S. Kawabata et al. Quasiparticle states of high-T[symbol] oxides observed by a Zeeman magnetic field response / S. Kashiwaya et al. Experimentally realizable devices for controlling the motion of magnetic flux quanta in anisotropic superconductors: vortex lenses, vortex diodes and vortex pumps / S. Savel'ev and F. Nori. Stability of vortex-antivortex "molecules" in mesoscopic superconducting triangles / V. R. Misko et al. Superconducting network with magnetic decoration - Hofstadter butterfly in spatially modulated magnetic field / Y. Iye et al. Observation of paramagnetic supercurrent in mesoscopic superconducting rings and disks using multiple-small-tunnel-junction method / A. Kanda et al. Guidance of vortices in high-T[stmbol] superconducting thin films with special arrangements of antidots / R. Wöerdenweber, P. Dymashevski and V. R. Misko. Quantum tunneling of relativistic fluxons / K. Konno et al. -- 6. Quantum information processing in solid states. Qubit decoherence by low-frequency noise / K. Rabenstein, V. A. Sverdlov and D. V. Averin. A critique of two-level approximation / K. Savran and T. Hakioǧlu. Josephson arrays as quantum channels / A. Romito, C. Bruder and R. Fazio. Fighting decoherence in a Josephson qubit circuit / E. Collin et al. Fast switching current detection at low critical currents / J. Walter, S. Corlevi and D. Haviland. Asymmetric flux bias for coupled qubits to observe entangled states / Y. Shimazu. Interaction of Josephson qubits with strong QED cavity modes: dynamical entanglement transfer and navigation / G. Falci et al. Controlling decoherence of transported quantum spin information in semiconductor spintronics / B. Nikolic and S. Souma. Decoherence due to telegraph and 1/f noise in Josephson qubits / E. Paladino et al. Detection of entanglement in NMR quantum information processing / R. Rahimi, K. Takeda and M. Kitagawa. Multiphoton absorption and SQUID switching current behaviors in superconducting flux-qubit experiments / H. Takayanagi et al. -- 7. Quantum information theory. Quantum query complexities / K. Iwama. A construction for non-stabilizer Clifford codes / M. Hagiwara and H. Imai. Quantum pushdown automata that can deterministically solve a certain problem / Y. Murakami et al. Trading classical for quantum computation using indirection / R. van Meter. Intractability of the initial arrangement of input data on qubits / Y. Kawano et al. Reversibility of modular squaring / N. Kunihiro, Y. Takahashi and Y. Kawano. Study of proximity effect at D-wave superconductors in quasiclassical methods / Y. Tanuma, Y. Tanaka and S. Kashiwaya -- 8. Spintronics in band electrons. Triplet superconductors: exploitable basis for scalable quantum computing / K. S. Wood et al. Spin excitations in low-dimensional electron gases studied by far-infrared photoconductivity spectroscopy / C.-M. Hu. Control of photogenerated carriers and spins using surface acoustic waves / P. V. Santos, J. A. H. Stotz and R. Hey. PbTe nanostructures for spin filtering and detecting / G. Grabecki. G-factor control in an Ids-inserted InGaAs/InAlAs heterostructure / J. Nitta et al. Spin hall effect in p-type semiconductors / S. Murakami. Spin diffusion in mesoscopic superconducting A1 wires / Y.-S. Shin. H.-J. Lee and H.-W. Lee. Magnetization processes revealed by in-plane DC magnetoresistance measurements on manganite bicrystal thin film devices / R. Gunnarsson. M. Hanson and T. Claeson. Giant magnetoconductance at interface between a two-dimensional hole system and a magnetic semiconductor (Ga, Mn)As / Y. Hashimoto, S. Katsumoto and Y. Iye. Diffusion modes of the transport in diluted magnetic semiconductors / I. Kanazawa. Effect of an invasive voltage probe on the spin polarized current / J. Ohe and T. Ohtsuki -- 9. Spintronics in quantum dots. Tunable exchange interaction and Kondo screening in quantum dot devices / H. Tamura et al. Kondo effect in quantum dots in presence of itinerant-electron magnetism / J. Martinek et al. Optical band edge of II-VI and III-V based diluted magnetic semiconductors / M. Takahashi. Spin-polarized transport properties through double quantum dots / Y. Tanaka and N. Kawakami. RKKY interaction between two quantum dots embedded in an Aharonov-Bohm ring / Y. Utsumi et al. Fabrication and characterization of quantum dot single electron spin resonance devices / T. Kodera et al. Kondo effect in quantum dots with two orbitals and spin 1/2 - crossover from SU (4) to SU (2) symmetry / M. Eto. Detecting spin polarization of electrons in quantum dot edge channels by photoluminescence / S. Nomura. Manipulation of exchange interaction in a double quantum dot / M. Stopa, S. Tarucha and T. Hatano. Electron-density dependence of photoluminescence from Be-[symbol]-doped GaAs quantum wells with a back gate / M. Yamaguchi et al. Direct observation of [symbol]Si nuclear-spin decoherence process / S. Sasaki and S. Watanabe.

Assembly, characterization, and operation of large-scale TES detector arrays for ACTPol

NASA Astrophysics Data System (ADS)

Pappas, Christine Goodwin

2016-01-01

The Polarization-sensitive Receiver for the Atacama Cosmology Telescope (ACTPol) is designed to measure the Cosmic Microwave Background (CMB) temperature and polarization anisotropies on small angular scales. Measurements of the CMB temperature and polarization anisotropies have produced arguably the most important cosmological data to date, establishing the LambdaCDM model and providing the best constraints on most of its parameters. To detect the very small fluctuations in the CMB signal across the sky, ACTPol uses feedhorn-coupled Transition-Edge Sensor (TES) detectors. A TES is a superconducting thin film operated in the transition region between the superconducting and normal states, where it functions as a highly sensitive resistive thermometer. In this thesis, aspects of the assembly, characterization, and in-field operation of the ACTPol TES detector arrays are discussed. First, a novel microfabrication process for producing high-density superconducting aluminum/polyimide flexible circuitry (flex) designed to connect large-scale detector arrays to the first stage of readout is presented. The flex is used in parts of the third ACTPol array and is currently being produced for use in the AdvACT detector arrays, which will begin to replace the ACTPol arrays in 2016. Next, we describe methods and results for the in-lab and on-telescope characterization of the detectors in the third ACTPol array. Finally, we describe the ACTPol TES R(T,I) transition shapes and how they affect the detector calibration and operation. Methods for measuring the exact detector calibration and re-biasing functions, taking into account the R(T,I) transition shape, are presented.

Magnetic relaxometry as applied to sensitive cancer detection and localization

DOE PAGES

De Haro, Leyma P.; Karaulanov, Todor; Vreeland, Erika C.; ...

2015-06-02

Abstract Here we describe superparamagnetic relaxometry (SPMR), a technology that utilizes highly sensitive magnetic sensors and superparamagnetic nanoparticles for cancer detection. Using SPMR, we sensitively and specifically detect nanoparticles conjugated to biomarkers for various types of cancer. SPMR offers high contrast In SPMR measurements, a brief magnetizing pulse is used to align superparamagnetic nanoparticles of a discrete size. Following the pulse, an array of superconducting quantum interference detectors (SQUID) sensors detect the decaying magnetization field. NP size is chosen so that, when bound, the induced field decays in seconds. They are functionalized with specific biomarkers and incubated with cancer cellsmore » As a result, superparamagnetic NPs developed here have small size dispersion. Cell incubation studies measure specificity for different cell lines and antibodies with very high contrast.« less

Method of making an improved superconducting quantum interference device

DOEpatents

Wu, Cheng-Teh; Falco, Charles M.; Kampwirth, Robert T.

1977-01-01

An improved superconducting quantum interference device is made by sputtering a thin film of an alloy of three parts niobium to one part tin in a pattern comprising a closed loop with a narrow region, depositing a thin film of a radiation shield such as copper over the niobium-tin, scribing a narrow line in the copper over the narrow region, exposing the structure at the scribed line to radiation and removing the deposited copper.

Superconducting Hot-Electron Submillimeter-Wave Detector

NASA Technical Reports Server (NTRS)

Karasik, Boris; McGrath, William; Leduc, Henry

2009-01-01

A superconducting hot-electron bolometer has been built and tested as a prototype of high-sensitivity, rapid-response detectors of submillimeter-wavelength radiation. There are diverse potential applications for such detectors, a few examples being submillimeter spectroscopy for scientific research; detection of leaking gases; detection of explosive, chemical, and biological weapons; and medical imaging. This detector is a superconducting-transition- edge device. Like other such devices, it includes a superconducting bridge that has a low heat capacity and is maintained at a critical temperature (T(sub c)) at the lower end of its superconducting-transition temperature range. Incident photons cause transient increases in electron temperature through the superconducting-transition range, thereby yielding measurable increases in electrical resistance. In this case, T(sub c) = 6 K, which is approximately the upper limit of the operating-temperature range of silicon-based bolometers heretofore used routinely in many laboratories. However, whereas the response speed of a typical silicon- based laboratory bolometer is characterized by a frequency of the order of a kilohertz, the response speed of the present device is much higher characterized by a frequency of the order of 100 MHz. For this or any bolometer, a useful figure of merit that one seeks to minimize is (NEP)(tau exp 1/2), where NEP denotes the noise-equivalent power (NEP) and the response time. This figure of merit depends primarily on the heat capacity and, for a given heat capacity, is approximately invariant. As a consequence of this approximate invariance, in designing a device having a given heat capacity to be more sensitive (to have lower NEP), one must accept longer response time (slower response) or, conversely, in designing it to respond faster, one must accept lower sensitivity. Hence, further, in order to increase both the speed of response and the sensitivity, one must make the device very small in order to make its heat capacity very small; this is the approach followed in developing the present device.

Phase transition with trivial quantum criticality in an anisotropic Weyl semimetal

NASA Astrophysics Data System (ADS)

Li, Xin; Wang, Jing-Rong; Liu, Guo-Zhu

2018-05-01

When a metal undergoes continuous quantum phase transition, the correlation length diverges at the critical point and the quantum fluctuation of order parameter behaves as a gapless bosonic mode. Generically, the coupling of this boson to fermions induces a variety of unusual quantum critical phenomena, such as non-Fermi liquid behavior and various emergent symmetries. Here, we perform a renormalization group analysis of the semimetal-superconductor quantum criticality in a three-dimensional anisotropic Weyl semimetal. Surprisingly, distinct from previously studied quantum critical systems, the anomalous dimension of anisotropic Weyl fermions flows to zero very quickly with decreasing energy, and the quasiparticle residue takes a nonzero value. These results indicate that the quantum fluctuation of superconducting order parameter is irrelevant at low energies, and a simple mean-field calculation suffices to capture the essential physics of the superconducting transition. We thus obtain a phase transition that exhibits trivial quantum criticality, which is unique comparing to other invariably nontrivial quantum critical systems. Our theoretical prediction can be experimentally verified by measuring the fermion spectral function and specific heat.

Exploring the quantum critical behaviour in a driven Tavis–Cummings circuit

PubMed Central

Feng, M.; Zhong, Y.P.; Liu, T.; Yan, L.L.; Yang, W.L.; Twamley, J.; Wang, H.

2015-01-01

Quantum phase transitions play an important role in many-body systems and have been a research focus in conventional condensed-matter physics over the past few decades. Artificial atoms, such as superconducting qubits that can be individually manipulated, provide a new paradigm of realising and exploring quantum phase transitions by engineering an on-chip quantum simulator. Here we demonstrate experimentally the quantum critical behaviour in a highly controllable superconducting circuit, consisting of four qubits coupled to a common resonator mode. By off-resonantly driving the system to renormalize the critical spin-field coupling strength, we have observed a four-qubit nonequilibrium quantum phase transition in a dynamical manner; that is, we sweep the critical coupling strength over time and monitor the four-qubit scaled moments for a signature of a structural change of the system's eigenstates. Our observation of the nonequilibrium quantum phase transition, which is in good agreement with the driven Tavis–Cummings theory under decoherence, offers new experimental approaches towards exploring quantum phase transition-related science, such as scaling behaviours, parity breaking and long-range quantum correlations. PMID:25971985

Temporal shaping of quantum states released from a superconducting cavity memory

NASA Astrophysics Data System (ADS)

Burkhart, L.; Axline, C.; Pfaff, W.; Zou, C.; Zhang, M.; Narla, A.; Frunzio, L.; Devoret, M. H.; Jiang, L.; Schoelkopf, R. J.

State transfer and entanglement distribution are essential primitives in network-based quantum information processing. We have previously demonstrated an interface between a quantum memory and propagating light fields in the microwave domain: by parametric conversion in a single Josephson junction, we have coherently released quantum states from a superconducting cavity resonator into a transmission line. Protocols for state transfer mediated by propagating fields typically rely on temporal mode-matching of couplings at both sender and receiver. However, parametric driving on a single junction results in dynamic frequency shifts, raising the question of whether the pumps alone provide enough control for achieving this mode-matching. We show, in theory and experiment, that phase and amplitude shaping of the parametric drives allows arbitrary control over the propagating field, limited only by the drives bandwidth and amplitude constraints. This temporal mode shaping technique allows for release and capture of quantum states, providing a credible route towards state transfer and entanglement generation in quantum networks in which quantum states are stored and processed in cavities.

Digital quantum simulators in a scalable architecture of hybrid spin-photon qubits

PubMed Central

Chiesa, Alessandro; Santini, Paolo; Gerace, Dario; Raftery, James; Houck, Andrew A.; Carretta, Stefano

2015-01-01

Resolving quantum many-body problems represents one of the greatest challenges in physics and physical chemistry, due to the prohibitively large computational resources that would be required by using classical computers. A solution has been foreseen by directly simulating the time evolution through sequences of quantum gates applied to arrays of qubits, i.e. by implementing a digital quantum simulator. Superconducting circuits and resonators are emerging as an extremely promising platform for quantum computation architectures, but a digital quantum simulator proposal that is straightforwardly scalable, universal, and realizable with state-of-the-art technology is presently lacking. Here we propose a viable scheme to implement a universal quantum simulator with hybrid spin-photon qubits in an array of superconducting resonators, which is intrinsically scalable and allows for local control. As representative examples we consider the transverse-field Ising model, a spin-1 Hamiltonian, and the two-dimensional Hubbard model and we numerically simulate the scheme by including the main sources of decoherence. PMID:26563516

Transport properties of ultrathin BaFe1.84Co0.16As2 superconducting nanowires

NASA Astrophysics Data System (ADS)

Yuan, Pusheng; Xu, Zhongtang; Li, Chen; Quan, Baogang; Li, Junjie; Gu, Changzhi; Ma, Yanwei

2018-07-01

Superconducting nanowire single-photon detectors (SNSPDs) have an absolute advantage over other types of single-photon detectors, except for the low operating temperature. Therefore, much effort has been devoted to finding high-temperature superconducting materials that are suitable for preparing SNSPDs. Copper-based and MgB2 ultrathin superconducting nanowires have already been reported. However, the transport properties of iron-based ultrathin superconducting nanowires have not been studied. In this work, a 10 nm thick × 200 nm wide × 30 μm long high-quality superconducting nanowire was fabricated from ultrathin BaFe1.84Co0.16As2 films by a lift-off process. The precursor BaFe1.84Co0.16As2 film with a thickness of 10 nm and root-mean-square roughness of 1 nm was grown on CaF2 substrates by pulsed laser deposition. The nanowire shows a high superconducting critical temperature {T}{{c}}{{zero}} = 20 K with a narrow transition width of ΔT = 2.5 K and exhibits a high critical current density J c of 1.8 × 107 A cm-2 at 10 K. These results of ultrathin BaFe1.84Co0.16As2 nanowire will attract interest in electronic applications, including SNSPDs.

Superconducting Bolometer Array Architectures

NASA Technical Reports Server (NTRS)

Benford, Dominic; Chervenak, Jay; Irwin, Kent; Moseley, S. Harvey; Shafer, Rick; Staguhn, Johannes; Wollack, Ed; Oegerle, William (Technical Monitor)

2002-01-01

The next generation of far-infrared and submillimeter instruments require large arrays of detectors containing thousands of elements. These arrays will necessarily be multiplexed, and superconducting bolometer arrays are the most promising present prospect for these detectors. We discuss our current research into superconducting bolometer array technologies, which has recently resulted in the first multiplexed detections of submillimeter light and the first multiplexed astronomical observations. Prototype arrays containing 512 pixels are in production using the Pop-Up Detector (PUD) architecture, which can be extended easily to 1000 pixel arrays. Planar arrays of close-packed bolometers are being developed for the GBT (Green Bank Telescope) and for future space missions. For certain applications, such as a slewed far-infrared sky survey, feedhorncoupling of a large sparsely-filled array of bolometers is desirable, and is being developed using photolithographic feedhorn arrays. Individual detectors have achieved a Noise Equivalent Power (NEP) of -10(exp 17) W/square root of Hz at 300mK, but several orders of magnitude improvement are required and can be reached with existing technology. The testing of such ultralow-background detectors will prove difficult, as this requires optical loading of below IfW. Antenna-coupled bolometer designs have advantages for large format array designs at low powers due to their mode selectivity.

Condensed Matter Theories: Volume 25

NASA Astrophysics Data System (ADS)

Ludeña, Eduardo V.; Bishop, Raymond F.; Iza, Peter

2011-03-01

pt. A. Fermi and Bose fluids, exotic systems. Reemergence of the collective mode in [symbol]He and electron layers / H. M. Bohm ... [et al.]. Dissecting and testing collective and topological scenarios for the quantum critical point / J. W. Clark, V. A. Khodel and M. V. Zverev. Helium on nanopatterned surfaces at finite temperature / E. S. Hernandez ... [et al.]. Towards DFT calculations of metal clusters in quantum fluid matrices / S. A. Chin ... [et al.]. Acoustic band gap formation in metamaterials / D. P. Elford ... [et al.]. Dissipative processes in low density strongly interacting 2D electron systems / D. Neilson. Dynamical spatially resolved response function of finite 1-D nano plasmas / T. Raitza, H. Reinholz and G. Ropke. Renormalized bosons and fermions / K. A. Gernoth and M. L. Ristig. Light clusters in nuclear matter / G. Ropke -- pt. B. Quantum magnets, quantum dynamics and phase transitions. Magnetic ordering of antiferromagnets on a spatially anisotropic triangular lattice / R. F. Bishop ... [et al.]. Thermodynamic detection of quantum phase transitions / M. K. G. Kruse ... [et al.]. The SU(2) semi quantum systems dynamics and thermodynamics / C. M. Sarris and A. N. Proto -- pt. C. Physics of nanosystems and nanotechnology. Quasi-one dimensional fluids that exhibit higher dimensional behavior / S. M. Gatica ... [et al.]. Spectral properties of molecular oligomers. A non-Markovian quantum state diffusion approach / J. Roden, W. T. Strunz and A. Eisfeld. Quantum properties in transport through nanoscopic rings: Charge-spin separation and interference effects / K. Hallberg, J. Rincon and S. Ramasesha. Cooperative localization-delocalization in the high T[symbol] cuprates / J. Ranninger. Thermodynamically stable vortex states in superconducting nanowires / W. M. Wu, M. B. Sobnack and F. V. Kusmartsev.pt. D. Quantum information. Quantum information in optical lattices / A. M. Guzman and M. A. Duenas E. -- pt. E. Theory and applications of molecular dynamics and density functional theory. Exchange-correlation functionals from the identical-particle Ornstein-Zernike equation: Basic formulation and numerical algorithms / R. Cuevas-Saavedra and P. W. Ayers. Features and catalytic properties of RhCu: A review / S. Gonzalez, C. Sousa and F. Illas. Kinetic energy functionals: Exact ones from analytic model wave functions and approximate ones in orbital-free molecular dynamics / V. V. Karasiev ... [et al.]. Numerical analysis of hydrogen storage in carbon nanopores / C. Wexler ... [et al.] -- pt. F. Superconductivity. Generalized Bose-Einstein condensation in superconductivity / M. de Llano. Kohn anomaly energy in conventional superconductors equals twice the energy of the superconducting gap: How and why? / R. Chaudhury and M. P. Das. Collective excitations in superconductors and semiconductors in the presence of a condensed phase / Z. Koinov. Thermal expansion of ferromagnetic superconductors: Possible application to UGe[symbol] / N. Hatayama and R. Konno. Generalized superconducting gap in a Boson-Fermion model / T. A. Mamedov and M. de Llano. Influence of domain walls in the superconductor/ferromagnet proximity effect / E. J. Patino. Spin singlet and triplet superconductivity induced by correlated hopping interactions / L. A. Perez, J. S. Millan and C. Wang -- pt. G. Statistical mechanics, relativistic quantum mechanics. Boltzmann's ergodic hypothesis: A meeting place for two cultures / M. H. Lee. Electron-electron interaction in the non-relativistic limit / F. B. Malik.

Linewidth Narrowing and Purcell Enhancement in Photonic Crystal Cavities on an Er-Doped Silicon Nitride Platform

DTIC Science & Technology

2010-02-01

Low noise superconducting single photon detectors on silicon,” Appl. Phys. Lett. 93, 131101 (2008). 20. M. T. Tanner, C. M. Natarajan, V. K... wavelength sensitivity in NbTiN superconducting nanowire single-photon detectors fabricated on oxidized silicon substrates,” Proceedings of Single...cavity resonance wavelength and Q-factor for the PC cavity are shown in Figure 3. The data are taken both at low (0.050 mW) pump power and high (30 mW

High-fidelity frequency down-conversion of visible entangled photon pairs with superconducting single-photon detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ikuta, Rikizo; Kato, Hiroshi; Kusaka, Yoshiaki

We experimentally demonstrate a high-fidelity visible-to-telecommunicationwavelength conversion of a photon by using a solid-state-based difference frequency generation. In the experiment, one half of a pico-second visible entangled photon pair at 780 nm is converted to a 1522-nm photon. Using superconducting single-photon detectors with low dark count rates and small timing jitters, we observed a fidelity of 0.93±0.04 after the wavelength conversion.

Encoding quantum information in a stabilized manifold of a superconducting cavity

NASA Astrophysics Data System (ADS)

Touzard, S.; Leghtas, Z.; Mundhada, S. O.; Axline, C.; Reagor, M.; Chou, K.; Blumoff, J.; Sliwa, K. M.; Shankar, S.; Frunzio, L.; Schoelkopf, R. J.; Mirrahimi, M.; Devoret, M. H.

In a superconducting Josephson circuit architecture, we activate a multi-photon process between two modes by applying microwave drives at specific frequencies. This creates a pairwise exchange of photons between a high-Q cavity and the environment. The resulting open dynamical system develops a two-dimensional quasi-energy ground state manifold. Can we encode, protect and manipulate quantum information in this manifold? We experimentally investigate the convergence and escape rates in and out of this confined subspace. Finally, using quantum Zeno dynamics, we aim to perform gates which maintain the state in the protected manifold at all times. Work supported by: ARO, ONR, AFOSR and YINQE.

Superconductive imaging surface magnetometer

DOEpatents

Overton, Jr., William C.; van Hulsteyn, David B.; Flynn, Edward R.

1991-01-01

An improved pick-up coil system for use with Superconducting Quantum Interference Device gradiometers and magnetometers involving the use of superconducting plates near conventional pick-up coil arrangements to provide imaging of nearby dipole sources and to deflect environmental magnetic noise away from the pick-up coils. This allows the practice of gradiometry and magnetometry in magnetically unshielded environments. One embodiment uses a hemispherically shaped superconducting plate with interior pick-up coils, allowing brain wave measurements to be made on human patients. another embodiment using flat superconducting plates could be used in non-destructive evaluation of materials.

Advanced ACTPol Cryogenic Detector Arrays and Readout

NASA Astrophysics Data System (ADS)

Henderson, S. W.; Allison, R.; Austermann, J.; Baildon, T.; Battaglia, N.; Beall, J. A.; Becker, D.; De Bernardis, F.; Bond, J. R.; Calabrese, E.; Choi, S. K.; Coughlin, K. P.; Crowley, K. T.; Datta, R.; Devlin, M. J.; Duff, S. M.; Dunkley, J.; Dünner, R.; van Engelen, A.; Gallardo, P. A.; Grace, E.; Hasselfield, M.; Hills, F.; Hilton, G. C.; Hincks, A. D.; Hloẑek, R.; Ho, S. P.; Hubmayr, J.; Huffenberger, K.; Hughes, J. P.; Irwin, K. D.; Koopman, B. J.; Kosowsky, A. B.; Li, D.; McMahon, J.; Munson, C.; Nati, F.; Newburgh, L.; Niemack, M. D.; Niraula, P.; Page, L. A.; Pappas, C. G.; Salatino, M.; Schillaci, A.; Schmitt, B. L.; Sehgal, N.; Sherwin, B. D.; Sievers, J. L.; Simon, S. M.; Spergel, D. N.; Staggs, S. T.; Stevens, J. R.; Thornton, R.; Van Lanen, J.; Vavagiakis, E. M.; Ward, J. T.; Wollack, E. J.

2016-08-01

Advanced ACTPol is a polarization-sensitive upgrade for the 6 m aperture Atacama Cosmology Telescope, adding new frequencies and increasing sensitivity over the previous ACTPol receiver. In 2016, Advanced ACTPol will begin to map approximately half the sky in five frequency bands (28-230 GHz). Its maps of primary and secondary cosmic microwave background anisotropies—imaged in intensity and polarization at few arcminute-scale resolution—will enable precision cosmological constraints and also a wide array of cross-correlation science that probes the expansion history of the universe and the growth of structure via gravitational collapse. To accomplish these scientific goals, the Advanced ACTPol receiver will be a significant upgrade to the ACTPol receiver, including four new multichroic arrays of cryogenic, feedhorn-coupled AlMn transition edge sensor polarimeters (fabricated on 150 mm diameter wafers); a system of continuously rotating meta-material silicon half-wave plates; and a new multiplexing readout architecture which uses superconducting quantum interference devices and time division to achieve a 64-row multiplexing factor. Here we present the status and scientific goals of the Advanced ACTPol instrument, emphasizing the design and implementation of the Advanced ACTPol cryogenic detector arrays.

Advanced ACTPol Cryogenic Detector Arrays and Readout

NASA Technical Reports Server (NTRS)

Henderson, S.W.; Allison, R.; Austermann, J.; Baildon, T.; Battaglia, N.; Beall, J. A.; Becker, D.; De Bernardis, F.; Bond, J. R.; Wollack, E. J.

2016-01-01

Advanced ACTPol is a polarization-sensitive upgrade for the 6 m aperture Atacama Cosmology Telescope, adding new frequencies and increasing sensitivity over the previous ACTPol receiver. In 2016, Advanced ACTPol will begin to map approximately half the sky in five frequency bands (28-230 GHz). Its maps of primary and secondary cosmic microwave background anisotropies-imaged in intensity and polarization at few arcminute-scale resolution-will enable precision cosmological constraints and also awide array of cross-correlation science that probes the expansion history of the universe and the growth of structure via gravitational collapse. To accomplish these scientific goals, the AdvancedACTPol receiver will be a significant upgrade to the ACTPol receiver, including four new multichroic arrays of cryogenic, feedhorn-coupled AlMn transition edge sensor polarimeters (fabricated on 150 mm diameter wafers); a system of continuously rotating meta-material silicon half-wave plates; and a new multiplexing readout architecture which uses superconducting quantum interference devices and time division to achieve a 64-row multiplexing factor. Here we present the status and scientific goals of the Advanced ACTPol instrument, emphasizing the design and implementation of the AdvancedACTPol cryogenic detector arrays.

Ballistic superconductivity in semiconductor nanowires.

PubMed

Zhang, Hao; Gül, Önder; Conesa-Boj, Sonia; Nowak, Michał P; Wimmer, Michael; Zuo, Kun; Mourik, Vincent; de Vries, Folkert K; van Veen, Jasper; de Moor, Michiel W A; Bommer, Jouri D S; van Woerkom, David J; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P A M; Quintero-Pérez, Marina; Cassidy, Maja C; Koelling, Sebastian; Goswami, Srijit; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo P

2017-07-06

Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor that enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices.

Quantum-limited heat conduction over macroscopic distances

NASA Astrophysics Data System (ADS)

Partanen, Matti; Tan, Kuan Yen; Govenius, Joonas; Lake, Russell E.; Mäkelä, Miika K.; Tanttu, Tuomo; Möttönen, Mikko

2016-05-01

The emerging quantum technological apparatuses, such as the quantum computer, call for extreme performance in thermal engineering. Cold distant heat sinks are needed for the quantized electric degrees of freedom owing to the increasing packaging density and heat dissipation. Importantly, quantum mechanics sets a fundamental upper limit for the flow of information and heat, which is quantified by the quantum of thermal conductance. However, the short distance between the heat-exchanging bodies in the previous experiments hinders their applicability in quantum technology. Here, we present experimental observations of quantum-limited heat conduction over macroscopic distances extending to a metre. We achieved this improvement of four orders of magnitude in the distance by utilizing microwave photons travelling in superconducting transmission lines. Thus, it seems that quantum-limited heat conduction has no fundamental distance cutoff. This work establishes the integration of normal-metal components into the framework of circuit quantum electrodynamics, which provides a basis for the superconducting quantum computer. Especially, our results facilitate remote cooling of nanoelectronic devices using faraway in situ-tunable heat sinks. Furthermore, quantum-limited heat conduction is important in contemporary thermodynamics. Here, the long distance may lead to ultimately efficient mesoscopic heat engines with promising practical applications.

Landau-Zener interferometry in a Cooper pair box

NASA Astrophysics Data System (ADS)

Sillanpää, Mika; Lehtinen, Teijo; Paila, Antti; Makhlin, Yuriy; Hakonen, Pertti

2006-03-01

Quantum-mechanical systems having two crossing energy levels are ubiquitous in nature. The rate v = d (E1- E0)/dt at which such levels in a driven system approach each other determines the probability PLZ of a Landau-Zener (LZ) tunneling between them. The traditional treatment of the LZ process, however, ignores quantum-mechanical interference. Here we report an observation of phase-sensitive interference between consecutive LZ tunneling attempts in an artificial two-state system, a superconducting charge qubit. We interpret the experiment in terms of a multi-pass analog to the optical Mach- Zehnder interferometer: The beam splitting occurs by LZ tunneling at the charge degeneracy, while the arms of the Mach- Zehnder interferometer in energy space are represented by the ground and excited state. In accord with theory, we observe constructive interference when the Stokes phase φS picked up during the LZ interaction, and the dynamical phase of one drive period φ= (E1- E0) dt satisfy the condition: (φ- 2 φS) = m .2π. Our LZ interferometer can be used as a high-resolution detector for phase and charge owing to interferometric sensitivity- enhancement.

Flux Noise due to Spins in SQUIDs

NASA Astrophysics Data System (ADS)

LaForest, Stephanie

Superconducting Quantum Interference Devices (SQUIDs) are currently being used as flux qubits and read-out detectors in a variety of solid-state quantum computer architectures. The main limitation of SQUID qubits is that they have a coherence time of the order of 10 micros, due to the presence of intrinsic flux noise that is not yet fully understood. The origin of flux noise is currently believed to be related to spin impurities present in the materials and interfaces that form the device. Here we present a novel numerical method that enables calculations of the flux produced by spin impurities even when they are located quite close to the SQUID wire. We show that the SQUID will be particularly sensitive to spins located at its wire edges, generating flux shifts of up to 4 nano flux quanta, much higher than previous calculations based on the software package FastHenry. This shows that spin impurities in a particular region along the wire's surface play a much more important role in producing flux noise than other spin impurities located elsewhere in the device.

Enabling Large Focal Plane Arrays Through Mosaic Hybridization

NASA Technical Reports Server (NTRS)

Miller, TImothy M.; Jhabvala, Christine A.; Leong, Edward; Costen, Nicholas P.; Sharp, Elmer; Adachi, Tomoko; Benford, Dominic

2012-01-01

We have demonstrated advances in mosaic hybridization that will enable very large format far-infrared detectors. Specifically we have produced electrical detector models via mosaic hybridization yielding superconducting circuit paths by hybridizing separately fabricated sub-units onto a single detector unit. The detector model was made on a 100mm diameter wafer while four model readout quadrant chips were made from a separate 100mm wafer. The individually fabricated parts were hybridized using a flip-chip bonder to assemble the detector-readout stack. Once all of the hybridized readouts were in place, a single, large and thick silicon substrate was placed on the stack and attached with permanent epoxy to provide strength and a Coefficient of Thermal Expansion match to the silicon components underneath. Wirebond pads on the readout chips connect circuits to warm readout electronics; and were used to validate the successful superconducting electrical interconnection of the model mosaic-hybrid detector. This demonstration is directly scalable to 150 mm diameter wafers, enabling pixel areas over ten times the area currently available.

Spectrum Tunable Quantum Dot-In-A-Well Infrared Detector Arrays for Thermal Imaging

DTIC Science & Technology

2008-09-01

Spectrum tunable quantum dot-in-a- well infrared detector arrays for thermal imaging Jonathan R. Andrews1, Sergio R. Restaino1, Scott W. Teare2...Materials at the University of New Mexico has been investigating quantum dot and quantum well detectors for thermal infrared imaging applications...SEP 2008 2. REPORT TYPE 3. DATES COVERED 00-00-2008 to 00-00-2008 4. TITLE AND SUBTITLE Spectrum tunable quantum dot-in-a- well infrared

Entanglement in a Quantum Annealing Processor

DTIC Science & Technology

2016-09-07

that QA is a viable technology for large- scale quantum computing . DOI: 10.1103/PhysRevX.4.021041 Subject Areas: Quantum Physics, Quantum Information...Superconductivity I. INTRODUCTION The past decade has been exciting for the field of quantum computation . A wide range of physical imple- mentations...measurements used in studying prototype universal quantum computers [9–14]. These constraints make it challenging to experimentally determine whether a scalable

Antenna-coupled Superconducting Bolometers for Observations of the Cosmic Microwave Background Polarization

NASA Astrophysics Data System (ADS)

Myers, Michael James

We describe the development of a novel millimeter-wave cryogenic detector. The device integrates a planar antenna, superconducting transmission line, bandpass filter, and bolometer onto a single silicon wafer. The bolometer uses a superconducting Transition-Edge Sensor (TES) thermistor, which provides substantial advantages over conventional semiconductor bolometers. The detector chip is fabricated using standard micro-fabrication techniques. This highly-integrated detector architecture is particularly well-suited for use in the de- velopment of polarization-sensitive cryogenic receivers with thousands of pixels. Such receivers are needed to meet the sensitivity requirements of next-generation cosmic microwave background polarization experiments. The design, fabrication, and testing of prototype array pixels are described. Preliminary considerations for a full array design are also discussed. A set of on-chip millimeter-wave test structures were developed to help understand the performance of our millimeter-wave microstrip circuits. These test structures produce a calibrated transmission measurement for an arbitrary two-port circuit using optical techniques, rather than a network analyzer. Some results of fabricated test structures are presented.

Disorder-induced half-integer quantized conductance plateau in quantum anomalous Hall insulator-superconductor structures

NASA Astrophysics Data System (ADS)

Huang, Yingyi; Setiawan, F.; Sau, Jay D.

2018-03-01

A weak superconducting proximity effect in the vicinity of the topological transition of a quantum anomalous Hall system has been proposed as a venue to realize a topological superconductor (TSC) with chiral Majorana edge modes (CMEMs). A recent experiment [Science 357, 294 (2017), 10.1126/science.aag2792] claimed to have observed such CMEMs in the form of a half-integer quantized conductance plateau in the two-terminal transport measurement of a quantum anomalous Hall-superconductor junction. Although the presence of a superconducting proximity effect generically splits the quantum Hall transition into two phase transitions with a gapped TSC in between, in this Rapid Communication we propose that a nearly flat conductance plateau, similar to that expected from CMEMs, can also arise from the percolation of quantum Hall edges well before the onset of the TSC or at temperatures much above the TSC gap. Our Rapid Communication, therefore, suggests that, in order to confirm the TSC, it is necessary to supplement the observation of the half-quantized conductance plateau with a hard superconducting gap (which is unlikely for a disordered system) from the conductance measurements or the heat transport measurement of the transport gap. Alternatively, the half-quantized thermal conductance would also serve as a smoking-gun signature of the TSC.

Tailoring Superconductivity with Quantum Dislocations.

PubMed

Li, Mingda; Song, Qichen; Liu, Te-Huan; Meroueh, Laureen; Mahan, Gerald D; Dresselhaus, Mildred S; Chen, Gang

2017-08-09

Despite the established knowledge that crystal dislocations can affect a material's superconducting properties, the exact mechanism of the electron-dislocation interaction in a dislocated superconductor has long been missing. Being a type of defect, dislocations are expected to decrease a material's superconducting transition temperature (T c ) by breaking the coherence. Yet experimentally, even in isotropic type I superconductors, dislocations can either decrease, increase, or have little influence on T c . These experimental findings have yet to be understood. Although the anisotropic pairing in dirty superconductors has explained impurity-induced T c reduction, no quantitative agreement has been reached in the case a dislocation given its complexity. In this study, by generalizing the one-dimensional quantized dislocation field to three dimensions, we reveal that there are indeed two distinct types of electron-dislocation interactions. Besides the usual electron-dislocation potential scattering, there is another interaction driving an effective attraction between electrons that is caused by dislons, which are quantized modes of a dislocation. The role of dislocations to superconductivity is thus clarified as the competition between the classical and quantum effects, showing excellent agreement with existing experimental data. In particular, the existence of both classical and quantum effects provides a plausible explanation for the illusive origin of dislocation-induced superconductivity in semiconducting PbS/PbTe superlattice nanostructures. A quantitative criterion has been derived, in which a dislocated superconductor with low elastic moduli and small electron effective mass and in a confined environment is inclined to enhance T c . This provides a new pathway for engineering a material's superconducting properties by using dislocations as an additional degree of freedom.

Three-Axis Superconducting Gravity Gradiometer

NASA Technical Reports Server (NTRS)

Paik, Ho Jung

1987-01-01

Gravity gradients measured even on accelerating platforms. Three-axis superconducting gravity gradiometer based on flux quantization and Meissner effect in superconductors and employs superconducting quantum interference device as amplifier. Incorporates several magnetically levitated proof masses. Gradiometer design integrates accelerometers for operation in differential mode. Principal use in commercial instruments for measurement of Earth-gravity gradients in geo-physical surveying and exploration for oil.

Inducing superconductivity in Weyl semimetal microstructures by selective ion sputtering.

PubMed

Bachmann, Maja D; Nair, Nityan; Flicker, Felix; Ilan, Roni; Meng, Tobias; Ghimire, Nirmal J; Bauer, Eric D; Ronning, Filip; Analytis, James G; Moll, Philip J W

2017-05-01

By introducing a superconducting gap in Weyl or Dirac semimetals, the superconducting state inherits the nontrivial topology of their electronic structure. As a result, Weyl superconductors are expected to host exotic phenomena, such as nonzero-momentum pairing due to their chiral node structure, or zero-energy Majorana modes at the surface. These are of fundamental interest to improve our understanding of correlated topological systems, and, moreover, practical applications in phase-coherent devices and quantum applications have been proposed. Proximity-induced superconductivity promises to allow these experiments on nonsuperconducting Weyl semimetals. We show a new route to reliably fabricate superconducting microstructures from the nonsuperconducting Weyl semimetal NbAs under ion irradiation. The significant difference in the surface binding energy of Nb and As leads to a natural enrichment of Nb at the surface during ion milling, forming a superconducting surface layer ( T c ~ 3.5 K). Being formed from the target crystal itself, the ideal contact between the superconductor and the bulk may enable an effective gapping of the Weyl nodes in the bulk because of the proximity effect. Simple ion irradiation may thus serve as a powerful tool for the fabrication of topological quantum devices from monoarsenides, even on an industrial scale.

Inducing superconductivity in Weyl semimetal microstructures by selective ion sputtering

PubMed Central

Bachmann, Maja D.; Nair, Nityan; Flicker, Felix; Ilan, Roni; Meng, Tobias; Ghimire, Nirmal J.; Bauer, Eric D.; Ronning, Filip; Analytis, James G.; Moll, Philip J. W.

2017-01-01

By introducing a superconducting gap in Weyl or Dirac semimetals, the superconducting state inherits the nontrivial topology of their electronic structure. As a result, Weyl superconductors are expected to host exotic phenomena, such as nonzero-momentum pairing due to their chiral node structure, or zero-energy Majorana modes at the surface. These are of fundamental interest to improve our understanding of correlated topological systems, and, moreover, practical applications in phase-coherent devices and quantum applications have been proposed. Proximity-induced superconductivity promises to allow these experiments on nonsuperconducting Weyl semimetals. We show a new route to reliably fabricate superconducting microstructures from the nonsuperconducting Weyl semimetal NbAs under ion irradiation. The significant difference in the surface binding energy of Nb and As leads to a natural enrichment of Nb at the surface during ion milling, forming a superconducting surface layer (Tc ~ 3.5 K). Being formed from the target crystal itself, the ideal contact between the superconductor and the bulk may enable an effective gapping of the Weyl nodes in the bulk because of the proximity effect. Simple ion irradiation may thus serve as a powerful tool for the fabrication of topological quantum devices from monoarsenides, even on an industrial scale. PMID:28560340

Quantum Criticality and Superconductivity in β-YbAlB4

NASA Astrophysics Data System (ADS)

Nakatsuji, Satoru

2009-03-01

Heavy fermion systems have provided a number of prototypical compounds to study unconventional superconductivity and non-Fermi-liquid (NFL) states. A long standing issue in the research of heavy fermion superconductivity in 4f intermetallics is the dramatically different behavior between the electron like Ce (4f^1) and hole like Yb (4f^13) compounds. While superconductivity has been found in a number of Ce based heavy fermion compounds, no superconductivity has been reported for the corresponding Yb systems. In this talk, I present our recent finding of the superconductivity in the new heavy fermion system β-YbAlB4 [1-3]. The superconducting transition temperature is 80 mK, and above it, the system exhibits pronounced NFL behavior in the transport and thermodynamic properties [2,3]. Furthermore, the magnetic field dependence of the NFL behavior indicates that the system is a rare example of a pure metal that displays quantum criticality at ambient pressure and under zero magnetic field. Using our latest results, we discuss the detailed properties of superconductivity and quantum criticality. This is the work performed in collaboration with K. Kuga, Y. Matsumoto, T. Tomita, Y. Machida, T. Tayama, T. Sakakibara, Y. Karaki, H. Ishimoto, S. Yonezawa, Y. Maeno, E. Pearson, G. G. Lonzarich, L.Balicas, H. Lee, and Z. Fisk. [4pt] [1] Robin T. Macaluso, Satoru Nakatsuji, Kentaro Kuga, Evan Lyle Thomas, Yo Machida, Yoshiteru Maeno, Zachary Fisk, and Julia Y. Chan, Chem. Mater. 19 1918 (2007). [0pt] [2] S. Nakatsuji, K.Kuga, Y. Machida, T. Tayama, T. Sakakibara, Y. Karaki, H. Ishimoto, S. Yonezawa, Y. Maeno, E. Pearson, G. G. Lonzarich, L.Balicas, H. Lee, and Z. Fisk, Nature Phys 4, 603-607 (2008). [0pt] [3] K. Kuga, Y. Karaki, Y. Matsumoto, Y. Machida, and S. Nakatsuji, Phys. Rev. Lett. 101, 137004 (2008).

Continuous quantum measurement with independent detector cross correlations.

PubMed

Jordan, Andrew N; Büttiker, Markus

2005-11-25

We investigate the advantages of using two independent, linear detectors for continuous quantum measurement. For single-shot measurement, the detection process may be quantum limited if the detectors are twins. For weak continuous measurement, cross correlations allow a violation of the Korotkov-Averin bound for the detector's signal-to-noise ratio. The joint weak measurement of noncommuting observables is also investigated, and we find the cross correlation changes sign as a function of frequency, reflecting a crossover from incoherent relaxation to coherent, out of phase oscillations. Our results are applied to a double quantum-dot charge qubit, simultaneously measured by two quantum point contacts.

A blueprint for demonstrating quantum supremacy with superconducting qubits

NASA Astrophysics Data System (ADS)

Neill, C.; Roushan, P.; Kechedzhi, K.; Boixo, S.; Isakov, S. V.; Smelyanskiy, V.; Megrant, A.; Chiaro, B.; Dunsworth, A.; Arya, K.; Barends, R.; Burkett, B.; Chen, Y.; Chen, Z.; Fowler, A.; Foxen, B.; Giustina, M.; Graff, R.; Jeffrey, E.; Huang, T.; Kelly, J.; Klimov, P.; Lucero, E.; Mutus, J.; Neeley, M.; Quintana, C.; Sank, D.; Vainsencher, A.; Wenner, J.; White, T. C.; Neven, H.; Martinis, J. M.

2018-04-01

A key step toward demonstrating a quantum system that can address difficult problems in physics and chemistry will be performing a computation beyond the capabilities of any classical computer, thus achieving so-called quantum supremacy. In this study, we used nine superconducting qubits to demonstrate a promising path toward quantum supremacy. By individually tuning the qubit parameters, we were able to generate thousands of distinct Hamiltonian evolutions and probe the output probabilities. The measured probabilities obey a universal distribution, consistent with uniformly sampling the full Hilbert space. As the number of qubits increases, the system continues to explore the exponentially growing number of states. Extending these results to a system of 50 qubits has the potential to address scientific questions that are beyond the capabilities of any classical computer.

Quantum Griffiths singularity of superconductor-metal transition in Ga thin films.

PubMed

Xing, Ying; Zhang, Hui-Min; Fu, Hai-Long; Liu, Haiwen; Sun, Yi; Peng, Jun-Ping; Wang, Fa; Lin, Xi; Ma, Xu-Cun; Xue, Qi-Kun; Wang, Jian; Xie, X C

2015-10-30

The Griffiths singularity in a phase transition, caused by disorder effects, was predicted more than 40 years ago. Its signature, the divergence of the dynamical critical exponent, is challenging to observe experimentally. We report the experimental observation of the quantum Griffiths singularity in a two-dimensional superconducting system. We measured the transport properties of atomically thin gallium films and found that the films undergo superconductor-metal transitions with increasing magnetic field. Approaching the zero-temperature quantum critical point, we observed divergence of the dynamical critical exponent, which is consistent with the Griffiths singularity behavior. We interpret the observed superconductor-metal quantum phase transition as the infinite-randomness critical point, where the properties of the system are controlled by rare large superconducting regions. Copyright © 2015, American Association for the Advancement of Science.

Develop of a quantum electromechanical hybrid system

NASA Astrophysics Data System (ADS)

Hao, Yu; Rouxinol, Francisco; Brito, Frederico; Caldeira, Amir; Irish, Elinor; Lahaye, Matthew

In this poster, we will show our results from measurements of a hybrid quantum system composed of a superconducting transmon qubit-coupled and ultra-high frequency nano-mechanical resonator, embedded in a superconducting cavity. The transmon is capacitively coupled to a 3.4GHz nanoresonator and a T-filter-biased high-Q transmission line cavity. Single-tone and two-tone transmission spectroscopy measurements are used to probe the interactions between the cavity, qubit and mechanical resonator. These measurements are in good agreement with numerical simulations based upon a master equation for the tripartite system including dissipation. The results indicate that this system may be developed to serve as a platform for more advanced measurements with nanoresonators, including quantum state measurement, the exploration of nanoresonator quantum noise, and reservoir engineering.

[Definition of quantum efficiency of X-ray detectors].

PubMed

Zelikman, M I

2001-01-01

Different definitions available in the literature on the quantum efficiency of X-ray detectors are presented and compared. The relationship of this parameter to spatial frequencies for quantum accounting receivers and energy accumulating ones is analyzed. A procedure is proposed for evaluating the quantum efficiency of the detectors in the area of zero spatial frequencies, which is rather simple and requires no special testing equipment.

Implementation of a quantum metamaterial using superconducting qubits.

PubMed

Macha, Pascal; Oelsner, Gregor; Reiner, Jan-Michael; Marthaler, Michael; André, Stephan; Schön, Gerd; Hübner, Uwe; Meyer, Hans-Georg; Il'ichev, Evgeni; Ustinov, Alexey V

2014-10-14

The key issue for the implementation of a metamaterial is to demonstrate the existence of collective modes corresponding to coherent oscillations of the meta-atoms. Atoms of natural materials interact with electromagnetic fields as quantum two-level systems. Artificial quantum two-level systems can be made, for example, using superconducting nonlinear resonators cooled down to their ground state. Here we perform an experiment in which 20 of these quantum meta-atoms, so-called flux qubits, are embedded into a microwave resonator. We observe the dispersive shift of the resonator frequency imposed by the qubit metamaterial and the collective resonant coupling of eight qubits. The realized prototype represents a mesoscopic limit of naturally occurring spin ensembles and as such we demonstrate the AC-Zeeman shift of a resonant qubit ensemble. The studied system constitutes the implementation of a basic quantum metamaterial in the sense that many artificial atoms are coupled collectively to the quantized mode of a photon field.

Engineering scalable fault-tolerant quantum computation

NASA Astrophysics Data System (ADS)

Kimchi-Schwartz, Mollie; Danna, Rosenberg; Kim, David; Yoder, Jonilyn; Kjaergaard, Morten; Das, Rabindra; Grover, Jeff; Gustavsson, Simon; Oliver, William

Recent demonstrations of quantum protocols comprising on the order of 5-10 superconducting qubits are foundational to the future development of quantum information processors. A next critical step in the development of resilient quantum processors will be the integration of coherent quantum circuits with a hardware platform that is amenable to extending the system size to hundreds of qubits and beyond. In this talk, we will discuss progress toward integrating coherent superconducting qubits with signal routing via the third dimension. This research was funded in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA) and by the Assistant Secretary of Defense for Research & Engineering under Air Force Contract No. FA8721-05-C-0002. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of ODNI, IARPA, or the US Government.

Probing the strongly driven spin-boson model in a superconducting quantum circuit.

PubMed

Magazzù, L; Forn-Díaz, P; Belyansky, R; Orgiazzi, J-L; Yurtalan, M A; Otto, M R; Lupascu, A; Wilson, C M; Grifoni, M

2018-04-11

Quantum two-level systems interacting with the surroundings are ubiquitous in nature. The interaction suppresses quantum coherence and forces the system towards a steady state. Such dissipative processes are captured by the paradigmatic spin-boson model, describing a two-state particle, the "spin", interacting with an environment formed by harmonic oscillators. A fundamental question to date is to what extent intense coherent driving impacts a strongly dissipative system. Here we investigate experimentally and theoretically a superconducting qubit strongly coupled to an electromagnetic environment and subjected to a coherent drive. This setup realizes the driven Ohmic spin-boson model. We show that the drive reinforces environmental suppression of quantum coherence, and that a coherent-to-incoherent transition can be achieved by tuning the drive amplitude. An out-of-equilibrium detailed balance relation is demonstrated. These results advance fundamental understanding of open quantum systems and bear potential for the design of entangled light-matter states.

Non-Poissonian Quantum Jumps of a Fluxonium Qubit due to Quasiparticle Excitations

NASA Astrophysics Data System (ADS)

Vool, U.; Pop, I. M.; Sliwa, K.; Abdo, B.; Wang, C.; Brecht, T.; Gao, Y. Y.; Shankar, S.; Hatridge, M.; Catelani, G.; Mirrahimi, M.; Frunzio, L.; Schoelkopf, R. J.; Glazman, L. I.; Devoret, M. H.

2014-12-01

As the energy relaxation time of superconducting qubits steadily improves, nonequilibrium quasiparticle excitations above the superconducting gap emerge as an increasingly relevant limit for qubit coherence. We measure fluctuations in the number of quasiparticle excitations by continuously monitoring the spontaneous quantum jumps between the states of a fluxonium qubit, in conditions where relaxation is dominated by quasiparticle loss. Resolution on the scale of a single quasiparticle is obtained by performing quantum nondemolition projective measurements within a time interval much shorter than T1 , using a quantum-limited amplifier (Josephson parametric converter). The quantum jump statistics switches between the expected Poisson distribution and a non-Poissonian one, indicating large relative fluctuations in the quasiparticle population, on time scales varying from seconds to hours. This dynamics can be modified controllably by injecting quasiparticles or by seeding quasiparticle-trapping vortices by cooling down in a magnetic field.

Quantum-statistical theory of microwave detection using superconducting tunnel junctions

NASA Astrophysics Data System (ADS)

Deviatov, I. A.; Kuzmin, L. S.; Likharev, K. K.; Migulin, V. V.; Zorin, A. B.

1986-09-01

A quantum-statistical theory of microwave and millimeter-wave detection using superconducting tunnel junctions is developed, with a rigorous account of quantum, thermal, and shot noise arising from fluctuation sources associated with the junctions, signal source, and matching circuits. The problem of the noise characterization in the quantum sensitivity range is considered and a general noise parameter Theta(N) is introduced. This parameter is shown to be an adequate figure of merit for most receivers of interest while some devices can require a more complex characterization. Analytical expressions and/or numerically calculated plots for Theta(N) are presented for the most promising detection modes including the parametric amplification, heterodyne mixing, and quadratic videodetection, using both the quasiparticle-current and the Cooper-pair-current nonlinearities. Ultimate minimum values of Theta(N) for each detection mode are compared and found to be in agreement with limitations imposed by the quantum-mechanical uncertainty principle.

Non-Poissonian quantum jumps of a fluxonium qubit due to quasiparticle excitations.

PubMed

Vool, U; Pop, I M; Sliwa, K; Abdo, B; Wang, C; Brecht, T; Gao, Y Y; Shankar, S; Hatridge, M; Catelani, G; Mirrahimi, M; Frunzio, L; Schoelkopf, R J; Glazman, L I; Devoret, M H

2014-12-12

As the energy relaxation time of superconducting qubits steadily improves, nonequilibrium quasiparticle excitations above the superconducting gap emerge as an increasingly relevant limit for qubit coherence. We measure fluctuations in the number of quasiparticle excitations by continuously monitoring the spontaneous quantum jumps between the states of a fluxonium qubit, in conditions where relaxation is dominated by quasiparticle loss. Resolution on the scale of a single quasiparticle is obtained by performing quantum nondemolition projective measurements within a time interval much shorter than T₁, using a quantum-limited amplifier (Josephson parametric converter). The quantum jump statistics switches between the expected Poisson distribution and a non-Poissonian one, indicating large relative fluctuations in the quasiparticle population, on time scales varying from seconds to hours. This dynamics can be modified controllably by injecting quasiparticles or by seeding quasiparticle-trapping vortices by cooling down in a magnetic field.

Deterministic quantum teleportation with feed-forward in a solid state system.

PubMed

Steffen, L; Salathe, Y; Oppliger, M; Kurpiers, P; Baur, M; Lang, C; Eichler, C; Puebla-Hellmann, G; Fedorov, A; Wallraff, A

2013-08-15

Engineered macroscopic quantum systems based on superconducting electronic circuits are attractive for experimentally exploring diverse questions in quantum information science. At the current state of the art, quantum bits (qubits) are fabricated, initialized, controlled, read out and coupled to each other in simple circuits. This enables the realization of basic logic gates, the creation of complex entangled states and the demonstration of algorithms or error correction. Using different variants of low-noise parametric amplifiers, dispersive quantum non-demolition single-shot readout of single-qubit states with high fidelity has enabled continuous and discrete feedback control of single qubits. Here we realize full deterministic quantum teleportation with feed-forward in a chip-based superconducting circuit architecture. We use a set of two parametric amplifiers for both joint two-qubit and individual qubit single-shot readout, combined with flexible real-time digital electronics. Our device uses a crossed quantum bus technology that allows us to create complex networks with arbitrary connecting topology in a planar architecture. The deterministic teleportation process succeeds with order unit probability for any input state, as we prepare maximally entangled two-qubit states as a resource and distinguish all Bell states in a single two-qubit measurement with high efficiency and high fidelity. We teleport quantum states between two macroscopic systems separated by 6 mm at a rate of 10(4) s(-1), exceeding other reported implementations. The low transmission loss of superconducting waveguides is likely to enable the range of this and other schemes to be extended to significantly larger distances, enabling tests of non-locality and the realization of elements for quantum communication at microwave frequencies. The demonstrated feed-forward may also find application in error correction schemes.

Further developments of series-connected superconducting tunnel junction to radiation detection

NASA Astrophysics Data System (ADS)

Kurakado, Masahiko; Ohsawa, Daisuke; Katano, Rintaro; Ito, Shin; Isozumi, Yasuhito

1997-10-01

One of the promising radiation detection devices for various practical applications is the series-connected superconducting tunnel junction (STJ) detector. In this article, interesting topics of the detectors are described since our previous work: e.g., more than two order higher detection efficiency compared with single STJ detectors, high count rate detection, and position resolution. Detectors were cooled to 0.35-0.4 K by means of a convenient 3He cryostat. The 5.9 and 6.5 keV x rays from 55Fe are separated by a detector specially designed for x-ray detection. The possible count rate of the series-junction detector estimated from the shaping-time constant applied in the measurements is high, e.g., over 104 counts per second. A series-junction detector equipped with a position sensing mechanism has shown a position resolution of about 35 μm in a sensing area with a radius of 1.1 mm. The position resolution of series junctions improves the energy resolution. A new type series-connected STJ detector is also proposed, i.e., the dispersed multitrap series-junction detector, for further improvement of detection efficiency and energy resolution.

Magnetic Sensitivity of AlMn TESes and Shielding Considerations for Next-Generation CMB Surveys

NASA Astrophysics Data System (ADS)

Vavagiakis, E. M.; Henderson, S. W.; Zheng, K.; Cho, H.-M.; Cothard, N. F.; Dober, B.; Duff, S. M.; Gallardo, P. A.; Hilton, G.; Hubmayr, J.; Irwin, K. D.; Koopman, B. J.; Li, D.; Nati, F.; Niemack, M. D.; Reintsema, C. D.; Simon, S.; Stevens, J. R.; Suzuki, A.; Westbrook, B.

2018-05-01

In the next decade, new ground-based cosmic microwave background (CMB) experiments such as Simons Observatory, CCAT-prime, and CMB-S4 will increase the number of detectors observing the CMB by an order of magnitude or more, dramatically improving our understanding of cosmology and astrophysics. These projects will deploy receivers with as many as hundreds of thousands of transition edge sensor (TES) bolometers coupled to superconducting quantum interference device (SQUID)-based readout systems. It is well known that superconducting devices such as TESes and SQUIDs are sensitive to magnetic fields. However, the effects of magnetic fields on TESes are not easily predicted due to the complex behavior of the superconducting transition, which motivates direct measurements of the magnetic sensitivity of these devices. We present comparative four-lead measurements of the critical temperature versus applied magnetic field of AlMn TESes varying in geometry, doping, and leg length, including Advanced ACT and POLARBEAR-2/Simons Array bolometers. MoCu ACTPol TESes are also tested and are found to be more sensitive to magnetic fields than the AlMn devices. We present an observation of weak-link-like behavior in AlMn TESes at low critical currents. We also compare measurements of magnetic sensitivity for time division multiplexing SQUIDs and frequency division multiplexing microwave (μ MUX) rf-SQUIDs. We discuss the implications of our measurements on the magnetic shielding required for future experiments that aim to map the CMB to near-fundamental limits.

High coherence plane breaking packaging for superconducting qubits.

PubMed

Bronn, Nicholas T; Adiga, Vivekananda P; Olivadese, Salvatore B; Wu, Xian; Chow, Jerry M; Pappas, David P

2018-04-01

We demonstrate a pogo pin package for a superconducting quantum processor specifically designed with a nontrivial layout topology (e.g., a center qubit that cannot be accessed from the sides of the chip). Two experiments on two nominally identical superconducting quantum processors in pogo packages, which use commercially available parts and require modest machining tolerances, are performed at low temperature (10 mK) in a dilution refrigerator and both found to behave comparably to processors in standard planar packages with wirebonds where control and readout signals come in from the edges. Single- and two-qubit gate errors are also characterized via randomized benchmarking, exhibiting similar error rates as in standard packages, opening the possibility of integrating pogo pin packaging with extensible qubit architectures.

High coherence plane breaking packaging for superconducting qubits

NASA Astrophysics Data System (ADS)

Bronn, Nicholas T.; Adiga, Vivekananda P.; Olivadese, Salvatore B.; Wu, Xian; Chow, Jerry M.; Pappas, David P.

2018-04-01

We demonstrate a pogo pin package for a superconducting quantum processor specifically designed with a nontrivial layout topology (e.g., a center qubit that cannot be accessed from the sides of the chip). Two experiments on two nominally identical superconducting quantum processors in pogo packages, which use commercially available parts and require modest machining tolerances, are performed at low temperature (10 mK) in a dilution refrigerator and both found to behave comparably to processors in standard planar packages with wirebonds where control and readout signals come in from the edges. Single- and two-qubit gate errors are also characterized via randomized benchmarking, exhibiting similar error rates as in standard packages, opening the possibility of integrating pogo pin packaging with extensible qubit architectures.

Demonstration of an ac Josephson junction laser

NASA Astrophysics Data System (ADS)

Cassidy, M. C.; Bruno, A.; Rubbert, S.; Irfan, M.; Kammhuber, J.; Schouten, R. N.; Akhmerov, A. R.; Kouwenhoven, L. P.

2017-03-01

Superconducting electronic devices have reemerged as contenders for both classical and quantum computing due to their fast operation speeds, low dissipation, and long coherence times. An ultimate demonstration of coherence is lasing. We use one of the fundamental aspects of superconductivity, the ac Josephson effect, to demonstrate a laser made from a Josephson junction strongly coupled to a multimode superconducting cavity. A dc voltage bias applied across the junction provides a source of microwave photons, and the circuit’s nonlinearity allows for efficient down-conversion of higher-order Josephson frequencies to the cavity’s fundamental mode. The simple fabrication and operation allows for easy integration with a range of quantum devices, allowing for efficient on-chip generation of coherent microwave photons at low temperatures.

Quantum heat engine with coupled superconducting resonators

NASA Astrophysics Data System (ADS)

Hardal, Ali Ü. C.; Aslan, Nur; Wilson, C. M.; Müstecaplıoǧlu, Özgür E.

2017-12-01

We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one due to the coupling. A limit cycle, indicating finite power output, emerges in the thermodynamical phase space. The system implements an all-electrical analog of a photonic piston. Instead of mechanical motion, the power output is obtained as a coherent electrical charging in our case. We explore the differences between the quantum and classical descriptions of our system by solving the quantum master equation and classical Langevin equations. Specifically, we calculate the mean number of excitations, second-order coherence, as well as the entropy, temperature, power, and mean energy to reveal the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures.

Quantum heat engine with coupled superconducting resonators.

PubMed

Hardal, Ali Ü C; Aslan, Nur; Wilson, C M; Müstecaplıoğlu, Özgür E

2017-12-01

We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one due to the coupling. A limit cycle, indicating finite power output, emerges in the thermodynamical phase space. The system implements an all-electrical analog of a photonic piston. Instead of mechanical motion, the power output is obtained as a coherent electrical charging in our case. We explore the differences between the quantum and classical descriptions of our system by solving the quantum master equation and classical Langevin equations. Specifically, we calculate the mean number of excitations, second-order coherence, as well as the entropy, temperature, power, and mean energy to reveal the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures.

Parametric resonance in tunable superconducting cavities

NASA Astrophysics Data System (ADS)

Wustmann, Waltraut; Shumeiko, Vitaly

2013-05-01

We develop a theory of parametric resonance in tunable superconducting cavities. The nonlinearity introduced by the superconducting quantum interference device (SQUID) attached to the cavity and damping due to connection of the cavity to a transmission line are taken into consideration. We study in detail the nonlinear classical dynamics of the cavity field below and above the parametric threshold for the degenerate parametric resonance, featuring regimes of multistability and parametric radiation. We investigate the phase-sensitive amplification of external signals on resonance, as well as amplification of detuned signals, and relate the amplifier performance to that of linear parametric amplifiers. We also discuss applications of the device for dispersive qubit readout. Beyond the classical response of the cavity, we investigate small quantum fluctuations around the amplified classical signals. We evaluate the noise power spectrum both for the internal field in the cavity and the output field. Other quantum-statistical properties of the noise are addressed such as squeezing spectra, second-order coherence, and two-mode entanglement.

Quantum dot single-photon switches of resonant tunneling current for discriminating-photon-number detection

PubMed Central

Weng, Qianchun; An, Zhenghua; Zhang, Bo; Chen, Pingping; Chen, Xiaoshuang; Zhu, Ziqiang; Lu, Wei

2015-01-01

Low-noise single-photon detectors that can resolve photon numbers are used to monitor the operation of quantum gates in linear-optical quantum computation. Exactly 0, 1 or 2 photons registered in a detector should be distinguished especially in long-distance quantum communication and quantum computation. Here we demonstrate a photon-number-resolving detector based on quantum dot coupled resonant tunneling diodes (QD-cRTD). Individual quantum-dots (QDs) coupled closely with adjacent quantum well (QW) of resonant tunneling diode operate as photon-gated switches- which turn on (off) the RTD tunneling current when they trap photon-generated holes (recombine with injected electrons). Proposed electron-injecting operation fills electrons into coupled QDs which turn “photon-switches” to “OFF” state and make the detector ready for multiple-photons detection. With proper decision regions defined, 1-photon and 2-photon states are resolved in 4.2 K with excellent propabilities of accuracy of 90% and 98% respectively. Further, by identifying step-like photon responses, the photon-number-resolving capability is sustained to 77 K, making the detector a promising candidate for advanced quantum information applications where photon-number-states should be accurately distinguished. PMID:25797442

Quantum dot single-photon switches of resonant tunneling current for discriminating-photon-number detection.

PubMed

Weng, Qianchun; An, Zhenghua; Zhang, Bo; Chen, Pingping; Chen, Xiaoshuang; Zhu, Ziqiang; Lu, Wei

2015-03-23

Low-noise single-photon detectors that can resolve photon numbers are used to monitor the operation of quantum gates in linear-optical quantum computation. Exactly 0, 1 or 2 photons registered in a detector should be distinguished especially in long-distance quantum communication and quantum computation. Here we demonstrate a photon-number-resolving detector based on quantum dot coupled resonant tunneling diodes (QD-cRTD). Individual quantum-dots (QDs) coupled closely with adjacent quantum well (QW) of resonant tunneling diode operate as photon-gated switches- which turn on (off) the RTD tunneling current when they trap photon-generated holes (recombine with injected electrons). Proposed electron-injecting operation fills electrons into coupled QDs which turn "photon-switches" to "OFF" state and make the detector ready for multiple-photons detection. With proper decision regions defined, 1-photon and 2-photon states are resolved in 4.2 K with excellent propabilities of accuracy of 90% and 98% respectively. Further, by identifying step-like photon responses, the photon-number-resolving capability is sustained to 77 K, making the detector a promising candidate for advanced quantum information applications where photon-number-states should be accurately distinguished.

Experimental formation of a fractional vortex in a superconducting bi-layer

NASA Astrophysics Data System (ADS)

Tanaka, Y.; Yamamori, H.; Yanagisawa, T.; Nishio, T.; Arisawa, S.

2018-05-01

We report the experimental formation of a fractional vortex generated by using a thin superconducting bi-layer in the form of a niobium bi-layer, observed as a magnetic flux distribution image taken by a scanning superconducting quantum interference device (SQUID) microscope. Thus, we demonstrated that multi-component superconductivity can be realized by an s-wave conventional superconductor, because, in these superconductors, the magnetic flux is no longer quantized as it is destroyed by the existence of an inter-component phase soliton (i-soliton).

Standoff passive video imaging at 350 GHz with 251 superconducting detectors

NASA Astrophysics Data System (ADS)

Becker, Daniel; Gentry, Cale; Smirnov, Ilya; Ade, Peter; Beall, James; Cho, Hsiao-Mei; Dicker, Simon; Duncan, William; Halpern, Mark; Hilton, Gene; Irwin, Kent; Li, Dale; Paulter, Nicholas; Reintsema, Carl; Schwall, Robert; Tucker, Carole

2014-06-01

Millimeter wavelength radiation holds promise for detection of security threats at a distance, including suicide bomb belts and maritime threats in poor weather. The high sensitivity of superconducting Transition Edge Sensor (TES) detectors makes them ideal for passive imaging of thermal signals at these wavelengths. We have built a 350 GHz video-rate imaging system using a large-format array of feedhorn-coupled TES bolometers. The system operates at a standoff distance of 16m to 28m with a spatial resolution of 1:4 cm (at 17m). It currently contains one 251-detector subarray, and will be expanded to contain four subarrays for a total of 1004 detectors. The system has been used to take video images which reveal the presence of weapons concealed beneath a shirt in an indoor setting. We present a summary of this work.

Fast and High Dynamic Range Imaging with Superconducting Tunnel Junction Detectors

NASA Astrophysics Data System (ADS)

Matsuo, Hiroshi

2014-08-01

We have demonstrated a combined test of the submillimeter-wave SIS photon detectors and GaAs-JFET cryogenic integrated circuits. A relatively large background photo-current can be read out by fast-reset integrating amplifiers. An integration time of 1 ms enables fast frame rate readout and large dynamic range imaging, with an expected dynamic range of 8,000 in 1 ms. Ultimate fast and high dynamic range performance of superconducting tunnel junction detectors (STJ) will be obtained when photon counting capabilities are employed. In the terahertz frequencies, when input photon rate of 100 MHz is measured, the photon bunching gives us enough timing resolution to be used as phase information of intensity fluctuation. Application of photon statistics will be a new tool in the terahertz frequency region. The design parameters of STJ terahertz photon counting detectors are discussed.

Emergence of superconductivity in heavy-electron materials

PubMed Central

Yang, Yi-feng; Pines, David

2014-01-01

Although the pairing glue for the attractive quasiparticle interaction responsible for unconventional superconductivity in heavy-electron materials has been identified as the spin fluctuations that arise from their proximity to a magnetic quantum critical point, there has been no model to describe their superconducting transition at temperature Tc that is comparable to that found by Bardeen, Cooper, and Schrieffer (BCS) for conventional superconductors, where phonons provide the pairing glue. Here we propose such a model: a phenomenological BCS-like expression for Tc in heavy-electron materials that is based on a simple model for the effective range and strength of the spin-fluctuation-induced quasiparticle interaction and reflects the unusual properties of the heavy-electron normal state from which superconductivity emerges. We show that it provides a quantitative understanding of the pressure-induced variation of Tc in the “hydrogen atoms” of unconventional superconductivity, CeCoIn5 and CeRhIn5, predicts scaling behavior and a dome-like structure for Tc in all heavy-electron quantum critical superconductors, provides unexpected connections between members of this family, and quantifies their variations in Tc with a single parameter. PMID:25489102

Process for Fabrication of Superconducting Vias for Electrical Connection to Groundplane in Cryogenic Detectors

NASA Technical Reports Server (NTRS)

Denis, Kevin L. (Inventor)

2018-01-01

Disclosed are systems, methods, and non-transitory computer-readable storage media for fabrication of silicon on insulator (SOI) wafers with a superconductive via for electrical connection to a groundplane. Fabrication of the SOI wafer with a superconductive via can involve depositing a superconducting groundplane onto a substrate with the superconducting groundplane having an oxidizing layer and a non-oxidizing layer. A layer of monocrystalline silicon can be bonded to the superconducting groundplane and a photoresist layer can be applied to the layer of monocrystalline silicon and the SOI wafer can be etched with the oxygen rich etching plasma, resulting in a monocrystalline silicon top layer with a via that exposes the superconducting groundplane. Then, the fabrication can involve depositing a superconducting surface layer to cover the via.

Superconducting Qubit with Integrated Single Flux Quantum Controller Part I: Theory and Fabrication

NASA Astrophysics Data System (ADS)

Beck, Matthew; Leonard, Edward, Jr.; Thorbeck, Ted; Zhu, Shaojiang; Howington, Caleb; Nelson, Jj; Plourde, Britton; McDermott, Robert

As the size of quantum processors grow, so do the classical control requirements. The single flux quantum (SFQ) Josephson digital logic family offers an attractive route to proximal classical control of multi-qubit processors. Here we describe coherent control of qubits via trains of SFQ pulses. We discuss the fabrication of an SFQ-based pulse generator and a superconducting transmon qubit on a single chip. Sources of excess microwave loss stemming from the complex multilayer fabrication of the SFQ circuit are discussed. We show how to mitigate this loss through judicious choice of process workflow and appropriate use of sacrificial protection layers. Present address: IBM T.J. Watson Research Center.

Heavy fermions, quantum criticality, and unconventional superconductivity in filled skutterudites and related materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andraka, Bohdan

2015-05-14

The main goal of this program was to explore the possibility of novel states and behaviors in Pr-based system exhibiting quantum critical behavior, PrOs₄Sb₁₂. Upon small changes of external parameter, such as magnetic field, physical properties of PrOs₄Sb₁₂ are drastically altered from those corresponding to a superconductor, to heavy fermion, to field-induced ordered phase with primary quadrupolar order parameter. All these states are highly unconventional and not understood in terms of current theories thus offer an opportunity to expand our knowledge and understanding of condensed matter. At the same time, these novel states and behaviors are subjects to intense internationalmore » controversies. In particular, two superconducting phases with different transition temperatures were observed in some samples and not observed in others leading to speculations that sample defects might be partially responsible for these exotic behaviors. This work clearly established that crystal disorder is important consideration, but contrary to current consensus this disorder suppresses exotic behavior. Superconducting properties imply unconventional inhomogeneous state that emerges from unconventional homogeneous normal state. Comprehensive structural investigations demonstrated that upper superconducting transition is intrinsic, bulk, and unconventional. The high quality of in-house synthesized single crystals was indirectly confirmed by de Haas-van Alphen quantum oscillation measurements. These measurements, for the first time ever reported, spanned several different phases, offering unprecedented possibility of studying quantum oscillations across phase boundaries.« less

Quantum nondemolition readout using a Josephson bifurcation amplifier

NASA Astrophysics Data System (ADS)

Boulant, N.; Ithier, G.; Meeson, P.; Nguyen, F.; Vion, D.; Esteve, D.; Siddiqi, I.; Vijay, R.; Rigetti, C.; Pierre, F.; Devoret, M.

2007-07-01

We report an experiment on the determination of the quantum nondemolition (QND) nature of a readout scheme of a quantum electrical circuit. The circuit is a superconducting quantum bit measured by microwave reflectometry using a Josephson bifurcation amplifier. We perform a series of two subsequent measurements, record their values and correlation, and quantify the QND character of this readout.

High Tc superconducting IR detectors from Y-Ba-Cu-O thin films

NASA Technical Reports Server (NTRS)

Lindgren, M.; Ahlberg, H.; Danerud, M.; Larsson, A.; Eng, M.

1990-01-01

A thin-film high-Tc superconducting multielement optical detector made of Y-Ba-Cu-O has been designed and evaluated using optical pulses from a diode laser (830 nm) and a Q-switched CO2-laser (10.6 microns). Different thin films have been tested. A laser deposited film showed the strongest response amplitude for short pulses and responded to an ultrafast, 50 ps wide pulse. Comparisons between dR/dT and response as a function of temperature indicated, however, a bolometric response.

A 2-D Array of Superconducting Magnesium Diboride (MgB2) Far-IR Thermal Detectors for Planetary Exploration

NASA Technical Reports Server (NTRS)

Lakew, Brook

2009-01-01

A 2-D array of superconducting Magnesium Diboride(MgB2) far IR thermal detectors has been fabricated. Such an array is intended to be at the focal plane of future generation thermal imaging far-IR instruments that will investigate the outer planets and their icy moons. Fabrication and processing of the pixels of the array as well as noise characterization of architectured MgB2 thin films will be presented. Challenges and solutions for improving the performance of the array will be discussed.

SCB Quantum Computers Using iSWAP and 1-Qubit Rotations

NASA Technical Reports Server (NTRS)

Williams, Colin; Echtemach, Pierre

2005-01-01

Units of superconducting circuitry that exploit the concept of the single- Cooper-pair box (SCB) have been built and are undergoing testing as prototypes of logic gates that could, in principle, constitute building blocks of clocked quantum computers. These units utilize quantized charge states as the quantum information-bearing degrees of freedom. An SCB is an artificial two-level quantum system that comprises a nanoscale superconducting electrode connected to a reservoir of Cooper-pair charges via a Josephson junction. The logical quantum states of the device, .0. and .1., are implemented physically as a pair of charge-number states that differ by 2e (where e is the charge of an electron). Typically, some 109 Cooper pairs are involved. Transitions between the logical states are accomplished by tunneling of Cooper pairs through the Josephson junction. Although the two-level system contains a macroscopic number of charges, in the superconducting regime, they behave collectively, as a Bose-Einstein condensate, making possible a coherent superposition of the two logical states. This possibility makes the SCB a candidate for the physical implementation of a qubit. A set of quantum logic operations and the gates that implement them is characterized as universal if, in principle, one can form combinations of the operations in the set to implement any desired quantum computation. To be able to design a practical quantum computer, one must first specify how to decompose any valid quantum computation into a sequence of elementary 1- and 2-qubit quantum gates that are universal and that can be realized in hardware that is feasible to fabricate. Traditionally, the set of universal gates has been taken to be the set of all 1-qubit quantum gates in conjunction with the controlled-NOT (CNOT) gate, which is a 2-qubit gate. Also, it has been known for some time that the SWAP gate, which implements square root of the simple 2-qubit exchange interaction, is as computationally universal as is the CNOT operation.

The Photon Shell Game and the Quantum von Neumann Architecture with Superconducting Circuits

NASA Astrophysics Data System (ADS)

Mariantoni, Matteo

2012-02-01

Superconducting quantum circuits have made significant advances over the past decade, allowing more complex and integrated circuits that perform with good fidelity. We have recently implemented a machine comprising seven quantum channels, with three superconducting resonators, two phase qubits, and two zeroing registers. I will explain the design and operation of this machine, first showing how a single microwave photon | 1 > can be prepared in one resonator and coherently transferred between the three resonators. I will also show how more exotic states such as double photon states | 2 > and superposition states | 0 >+ | 1 > can be shuffled among the resonators as well [1]. I will then demonstrate how this machine can be used as the quantum-mechanical analog of the von Neumann computer architecture, which for a classical computer comprises a central processing unit and a memory holding both instructions and data. The quantum version comprises a quantum central processing unit (quCPU) that exchanges data with a quantum random-access memory (quRAM) integrated on one chip, with instructions stored on a classical computer. I will also present a proof-of-concept demonstration of a code that involves all seven quantum elements: (1), Preparing an entangled state in the quCPU, (2), writing it to the quRAM, (3), preparing a second state in the quCPU, (4), zeroing it, and, (5), reading out the first state stored in the quRAM [2]. Finally, I will demonstrate that the quantum von Neumann machine provides one unit cell of a two-dimensional qubit-resonator array that can be used for surface code quantum computing. This will allow the realization of a scalable, fault-tolerant quantum processor with the most forgiving error rates to date. [4pt] [1] M. Mariantoni et al., Nature Physics 7, 287-293 (2011.)[0pt] [2] M. Mariantoni et al., Science 334, 61-65 (2011).

Compressed Sensing Quantum Process Tomography for Superconducting Quantum Gates

NASA Astrophysics Data System (ADS)

Rodionov, Andrey

An important challenge in quantum information science and quantum computing is the experimental realization of high-fidelity quantum operations on multi-qubit systems. Quantum process tomography (QPT) is a procedure devised to fully characterize a quantum operation. We first present the results of the estimation of the process matrix for superconducting multi-qubit quantum gates using the full data set employing various methods: linear inversion, maximum likelihood, and least-squares. To alleviate the problem of exponential resource scaling needed to characterize a multi-qubit system, we next investigate a compressed sensing (CS) method for QPT of two-qubit and three-qubit quantum gates. Using experimental data for two-qubit controlled-Z gates, taken with both Xmon and superconducting phase qubits, we obtain estimates for the process matrices with reasonably high fidelities compared to full QPT, despite using significantly reduced sets of initial states and measurement configurations. We show that the CS method still works when the amount of data is so small that the standard QPT would have an underdetermined system of equations. We also apply the CS method to the analysis of the three-qubit Toffoli gate with simulated noise, and similarly show that the method works well for a substantially reduced set of data. For the CS calculations we use two different bases in which the process matrix is approximately sparse (the Pauli-error basis and the singular value decomposition basis), and show that the resulting estimates of the process matrices match with reasonably high fidelity. For both two-qubit and three-qubit gates, we characterize the quantum process by its process matrix and average state fidelity, as well as by the corresponding standard deviation defined via the variation of the state fidelity for different initial states. We calculate the standard deviation of the average state fidelity both analytically and numerically, using a Monte Carlo method. Overall, we show that CS QPT offers a significant reduction in the needed amount of experimental data for two-qubit and three-qubit quantum gates.

Physical implementation of protected qubits

NASA Astrophysics Data System (ADS)

Douçot, B.; Ioffe, L. B.

2012-07-01

We review the general notion of topological protection of quantum states in spin models and its relation with the ideas of quantum error correction. We show that topological protection can be viewed as a Hamiltonian realization of error correction: for a quantum code for which the minimal number of errors that remain undetected is N, the corresponding Hamiltonian model of the effects of the environment noise appears only in the Nth order of the perturbation theory. We discuss the simplest model Hamiltonians that realize topological protection and their implementation in superconducting arrays. We focus on two dual realizations: in one the protected state is stored in the parity of the Cooper pair number, in the other, in the parity of the flux number. In both cases the superconducting arrays allow a number of fault-tolerant operations that should make the universal quantum computation possible.

Observing a quantum Maxwell demon at work

NASA Astrophysics Data System (ADS)

Cottet, Nathanaël; Jezouin, Sébastien; Bretheau, Landry; Campagne-Ibarcq, Philippe; Ficheux, Quentin; Anders, Janet; Auffèves, Alexia; Azouit, Rémi; Rouchon, Pierre; Huard, Benjamin

2017-07-01

In apparent contradiction to the laws of thermodynamics, Maxwell’s demon is able to cyclically extract work from a system in contact with a thermal bath, exploiting the information about its microstate. The resolution of this paradox required the insight that an intimate relationship exists between information and thermodynamics. Here, we realize a Maxwell demon experiment that tracks the state of each constituent in both the classical and quantum regimes. The demon is a microwave cavity that encodes quantum information about a superconducting qubit and converts information into work by powering up a propagating microwave pulse by stimulated emission. Thanks to the high level of control of superconducting circuits, we directly measure the extracted work and quantify the entropy remaining in the demon’s memory. This experiment provides an enlightening illustration of the interplay of thermodynamics with quantum information.

QUANTUM INFORMATION. Coherent coupling between a ferromagnetic magnon and a superconducting qubit.

PubMed

Tabuchi, Yutaka; Ishino, Seiichiro; Noguchi, Atsushi; Ishikawa, Toyofumi; Yamazaki, Rekishu; Usami, Koji; Nakamura, Yasunobu

2015-07-24

Rigidity of an ordered phase in condensed matter results in collective excitation modes spatially extending to macroscopic dimensions. A magnon is a quantum of such collective excitation modes in ordered spin systems. Here, we demonstrate the coherent coupling between a single-magnon excitation in a millimeter-sized ferromagnetic sphere and a superconducting qubit, with the interaction mediated by the virtual photon excitation in a microwave cavity. We obtain the coupling strength far exceeding the damping rates, thus bringing the hybrid system into the strong coupling regime. Furthermore, we use a parametric drive to realize a tunable magnon-qubit coupling scheme. Our approach provides a versatile tool for quantum control and measurement of the magnon excitations and may lead to advances in quantum information processing. Copyright © 2015, American Association for the Advancement of Science.

Experimental realization of universal geometric quantum gates with solid-state spins.

PubMed

Zu, C; Wang, W-B; He, L; Zhang, W-G; Dai, C-Y; Wang, F; Duan, L-M

2014-10-02

Experimental realization of a universal set of quantum logic gates is the central requirement for the implementation of a quantum computer. In an 'all-geometric' approach to quantum computation, the quantum gates are implemented using Berry phases and their non-Abelian extensions, holonomies, from geometric transformation of quantum states in the Hilbert space. Apart from its fundamental interest and rich mathematical structure, the geometric approach has some built-in noise-resilience features. On the experimental side, geometric phases and holonomies have been observed in thermal ensembles of liquid molecules using nuclear magnetic resonance; however, such systems are known to be non-scalable for the purposes of quantum computing. There are proposals to implement geometric quantum computation in scalable experimental platforms such as trapped ions, superconducting quantum bits and quantum dots, and a recent experiment has realized geometric single-bit gates in a superconducting system. Here we report the experimental realization of a universal set of geometric quantum gates using the solid-state spins of diamond nitrogen-vacancy centres. These diamond defects provide a scalable experimental platform with the potential for room-temperature quantum computing, which has attracted strong interest in recent years. Our experiment shows that all-geometric and potentially robust quantum computation can be realized with solid-state spin quantum bits, making use of recent advances in the coherent control of this system.

Undoing measurement-induced dephasing in circuit QED

NASA Astrophysics Data System (ADS)

Frisk Kockum, A.; Tornberg, L.; Johansson, G.

2012-05-01

We analyze the backaction of homodyne detection and photodetection on superconducting qubits in circuit quantum electrodynamics. Although both measurement schemes give rise to backaction in the form of stochastic phase rotations, which leads to dephasing, we show that this can be perfectly undone provided that the measurement signal is fully accounted for. This result improves on an earlier one [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.82.012329 82, 012329 (2010)], showing that the method suggested can be made to realize a perfect two-qubit parity measurement. We propose a benchmarking experiment on a single qubit to demonstrate the method using homodyne detection. By analyzing the limited measurement efficiency of the detector and bandwidth of the amplifier, we show that the parameter values necessary to see the effect are within the limits of existing technology.

A hidden pseudogap under the 'dome' of superconductivity in electron-doped high-temperature superconductors.

PubMed

Alff, L; Krockenberger, Y; Welter, B; Schonecke, M; Gross, R; Manske, D; Naito, M

2003-04-17

The ground state of superconductors is characterized by the long-range order of condensed Cooper pairs: this is the only order present in conventional superconductors. The high-transition-temperature (high-T(c)) superconductors, in contrast, exhibit more complex phase behaviour, which might indicate the presence of other competing ground states. For example, the pseudogap--a suppression of the accessible electronic states at the Fermi level in the normal state of high-T(c) superconductors-has been interpreted as either a precursor to superconductivity or as tracer of a nearby ground state that can be separated from the superconducting state by a quantum critical point. Here we report the existence of a second order parameter hidden within the superconducting phase of the underdoped (electron-doped) high-T(c) superconductor Pr2-xCe(x)CuO4-y and the newly synthesized electron-doped material La2-xCe(x)CuO4-y (ref. 8). The existence of a pseudogap when superconductivity is suppressed excludes precursor superconductivity as its origin. Our observation is consistent with the presence of a (quantum) phase transition at T = 0, which may be a key to understanding high-T(c) superconductivity. This supports the picture that the physics of high-T(c) superconductors is determined by the interplay between competing and coexisting ground states.

Multiband nodeless superconductivity near the charge-density-wave quantum critical point in ZrTe3-x Se x

NASA Astrophysics Data System (ADS)

Shan, Cui; Lan-Po, He; Xiao-Chen, Hong; Xiang-De, Zhu; Cedomir, Petrovic; Shi-Yan, Li

2016-07-01

It was found that selenium doping can suppress the charge-density-wave (CDW) order and induce bulk superconductivity in ZrTe3. The observed superconducting dome suggests the existence of a CDW quantum critical point (QCP) in ZrTe3-x Se x near x ≈ 0.04. To elucidate the superconducting state near the CDW QCP, we measure the thermal conductivity of two ZrTe3-x Se x single crystals (x = 0.044 and 0.051) down to 80 mK. For both samples, the residual linear term κ 0/T at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependence of κ 0/T manifests a multigap behavior. These results demonstrate multiple nodeless superconducting gaps in ZrTe3-x Se x , which indicates conventional superconductivity despite of the existence of a CDW QCP. Project supported by the National Basic Research Program of China (Grant Nos. 2012CB821402 and 2015CB921401), the National Natural Science Foundation of China (Grant Nos. 91421101, 11422429, and 11204312), the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning, China, and STCSM of China (Grant No. 15XD1500200). Work at Brookhaven National Laboratory was supported by the US DOE under Contract No. DESC00112704.

Amplitude distributions of dark counts and photon counts in NbN superconducting single-photon detectors integrated with the HEMT readout

NASA Astrophysics Data System (ADS)

Kitaygorsky, J.; Słysz, W.; Shouten, R.; Dorenbos, S.; Reiger, E.; Zwiller, V.; Sobolewski, Roman

2017-01-01

We present a new operation regime of NbN superconducting single-photon detectors (SSPDs) by integrating them with a low-noise cryogenic high-electron-mobility transistor and a high-load resistor. The integrated sensors are designed to get a better understanding of the origin of dark counts triggered by the detector, as our scheme allows us to distinguish the origin of dark pulses from the actual photon pulses in SSPDs. The presented approach is based on a statistical analysis of amplitude distributions of recorded trains of the SSPD photoresponse transients. It also enables to obtain information on energy of the incident photons, as well as demonstrates some photon-number-resolving capability of meander-type SSPDs.

The DCU: the detector control unit of the SAFARI instrument onboard SPICA

NASA Astrophysics Data System (ADS)

Clénet, A.; Ravera, L.; Bertrand, B.; Cros, A.; Hou, R.; Jackson, B. D.; van Leeuwen, B. J.; Van Loon, D.; Parot, Y.; Pointecouteau, E.; Sournac, A.; Ta, N.

2012-09-01

The SpicA FAR infrared Instrument (SAFARI) is a European instrument for the infrared domain telescope SPICA, a JAXA space mission. The SAFARI detectors are Transistor Edge Sensors (TES) arranged in 3 matrixes. The TES front end electronic is based on Superconducting Quantum Interference Devices (SQUIDs) and it does the readout of the 3500 detectors with Frequency Division Multiplexing (FDM) type architecture. The Detector Control Unit (DCU), contributed by IRAP, manages the readout of the TES by computing and providing the AC-bias signals (1 - 3 MHz) to the TES and by computing the demodulation of the returning signals. The SQUID being highly non-linear, the DCU has also to provide a feedback signal to increase the SQUID dynamic. Because of the propagation delay in the cables and the processing time, a classic feedback will not be stable for AC-bias frequencies up to 3 MHz. The DCU uses a specific technique to compensate for those delays: the BaseBand FeedBack (BBFB). This digital data processing is done for the 3500 pixels in parallel. Thus, to keep the DCU power budget within its allocation we have to specifically optimize the architecture of the digital circuit with respect to the power consumption. In this paper we will mainly present the DCU architecture. We will particularly focus on the BBFB technique used to linearize the SQUID and on the optimization done to reduce the power consumption of the digital processing circuit.

Lithographed Superconducting Resonator Development for Next-Generation Frequency Multiplexing Readout of Transition-Edge Sensors

NASA Astrophysics Data System (ADS)

Faramarzi, F.; De Haan, T.; Kusaka, A.; Lee, A.; Neuhauser, B.; Plambeck, R.; Raum, C.; Suzuki, A.; Westbrook, B.

2018-03-01

Ground-based cosmic microwave background (CMB) experiments are undergoing a period of exponential growth. Current experiments are observing with 1000-10,000 detectors, and the next-generation experiment (CMB stage 4) is proposing to deploy approximately 500,000 detectors. This order of magnitude increase in detector count will require a new approach for readout electronics. We have developed superconducting resonators for next-generation frequency-domain multiplexing (fMUX) readout architecture. Our goal is to reduce the physical size of resonators, such that resonators and detectors can eventually be integrated on a single wafer. To reduce the size of these resonators, we have designed spiral inductors and interdigitated capacitors that resonate around 10-100 MHz, an order of magnitude higher frequency compared to current fMUX readout systems. The higher frequency leads to a wider bandwidth and would enable higher multiplexing factor than the current ˜ 50 detectors per readout channel. We will report on the simulation, fabrication method, characterization technique, and measurement of quality factor of these resonators.

Field-induced reentrant superconductivity driven by quantum tricritical fluctuations in URhGe

NASA Astrophysics Data System (ADS)

Tokunaga, Y.; Aoki, D.; Mayaffre, H.; Krämer, S.; Julien, M.-H.; Berthier, C.; Horvatić, M.; Sakai, H.; Hattori, T.; Kambe, S.; Araki, S.

2018-05-01

We review our 59Co NMR study in a URhGe single crystal doped with 10% cobalt. The spin-spin relaxation time (T2) measurements have revealed a divergence of electronic spin fluctuations in the vicinity of a field-induced tricritical point (TCP) locating around 13 T. The fluctuations is developed in the same limited field region around the TCP as that where a reentrant superconductivity (RSC) is observed in URhGe. The finding strongly suggests these quantum fluctuations as the pairing glue responsible for the RSC.

A note on quantum teleportation without the Bell-state measurement in superconducting qubits

NASA Astrophysics Data System (ADS)

Gomes, R. M.; Cardoso, W. B.; Avelar, A. T.; Baseia, B.

2014-02-01

In this paper, we offer a simple scheme to teleport a quantum state from a superconducting qubit to another spatially separated qubit, both coupled to coplanar waveguide microwave resonator. In this scheme the Bell-state measurement is not necessary, which simplifies the experimental observation. We revisit the effective model that describes such a coupled system and present the teleportation scheme with 98.7% of fidelity and 25% of success probability. We also verify the feasibility of this protocol for the transmon qubit parameters.

A Bowtie Antenna Coupled Tunable Photon-Assisted Tunneling Double Quantum Well (DQW) THz Detector

DTIC Science & Technology

2002-01-01

Proc. Vol. 692 © 2002 Materials Research Society H4.2 A Bowtie Antenna Coupled Tunable Photon-Assisted Tunneling Double Quantum Well (DQW) THz Detector ...on photon-assisted tunneling (PAT) between the two electron layers in a double quantum well (DQW) heterostructure, will be explained. The detector is...the frequency and strength of that radiation. The THz detector discussed in this paper makes use of photon- assisted tunnelling (PAT) between multiple

Competing Quantum Orderings in Cuprate Superconductors:

NASA Astrophysics Data System (ADS)

Martin, I.; Ortiz, G.; Balatsky, A. V.; Bishop, A. R.

We present a minimal model for cuprate superconductors. At the unrestricted mean-field level, the model produces homogeneous superconductivity at large doping, striped superconductivity in the underdoped regime and various antiferromagnetic phases at low doping and for high temperatures. On the underdoped side, the superconductor is intrinsically inhomogeneous and global phase coherence is achieved through Josephson-like coupling of the superconducting stripes. The model is applied to calculate experimentally measurable ARPES spectra.

Inducing superconductivity in Weyl semimetal microstructures by selective ion sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bachmann, Maja D.; Nair, Nityan; Flicker, Felix

By introducing a superconducting gap in Weyl or Dirac semimetals, the superconducting state inherits the nontrivial topology of their electronic structure. As a result, Weyl superconductors are expected to host exotic phenomena, such as nonzero-momentum pairing due to their chiral node structure, or zero-energy Majorana modes at the surface. These are of fundamental interest to improve our understanding of correlated topological systems, and, moreover, practical applications in phase-coherent devices and quantum applications have been proposed. Proximity-induced superconductivity promises to allow these experiments on nonsuperconducting Weyl semimetals. Here, we show a new route to reliably fabricate superconducting microstructures from the nonsuperconductingmore » Weyl semimetal NbAs under ion irradiation. Furthermore, the significant difference in the surface binding energy of Nb and As leads to a natural enrichment of Nb at the surface during ion milling, forming a superconducting surface layer (Tc ~ 3.5 K). Being formed from the target crystal itself, the ideal contact between the superconductor and the bulk may enable an effective gapping of the Weyl nodes in the bulk because of the proximity effect. Simple ion irradiation may thus serve as a powerful tool for the fabrication of topological quantum devices from monoarsenides, even on an industrial scale.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goldman, Allen M.

The goal of this program was to study new physical phenomena that might be relevant to the performance of conductive devices and circuits of the smallest realizable feature sizes possible using physical rather than biological techniques. Although the initial scientific work supported involved the use of scanning tunneling microscopy and spectroscopy to ascertain the statistics of the energy level distribution of randomly sized and randomly shaped quantum dots, or nano-crystals, the main focus was on the investigation of selected properties, including superconductivity, of conducting and superconducting nanowires prepared using electron-beam-lithography. We discovered a magnetic-field-restoration of superconductivity in out-of-equilibrium nanowires drivenmore » resistive by current. This phenomenon was explained by the existence of a state in which dissipation coexisted with nonvanishing superconducting order. We also produced ultra-small superconducting loops to study a predicted anomalous fluxoid quantization, but instead, found a magnetic-field-dependent, high-resistance state, rather than superconductivity. Finally, we developed a simple and controllable nanowire in an induced charged layer near the surface of a masked single-crystal insulator, SrTiO 3. The layer was induced using an electric double layer transistor employing an ionic liquid (IL). The transport properties of the induced nanowire resembled those of collective electronic transport through an array of quantum dots.« less

Inducing superconductivity in Weyl semimetal microstructures by selective ion sputtering

DOE PAGES

Bachmann, Maja D.; Nair, Nityan; Flicker, Felix; ...

2017-05-24

By introducing a superconducting gap in Weyl or Dirac semimetals, the superconducting state inherits the nontrivial topology of their electronic structure. As a result, Weyl superconductors are expected to host exotic phenomena, such as nonzero-momentum pairing due to their chiral node structure, or zero-energy Majorana modes at the surface. These are of fundamental interest to improve our understanding of correlated topological systems, and, moreover, practical applications in phase-coherent devices and quantum applications have been proposed. Proximity-induced superconductivity promises to allow these experiments on nonsuperconducting Weyl semimetals. Here, we show a new route to reliably fabricate superconducting microstructures from the nonsuperconductingmore » Weyl semimetal NbAs under ion irradiation. Furthermore, the significant difference in the surface binding energy of Nb and As leads to a natural enrichment of Nb at the surface during ion milling, forming a superconducting surface layer (Tc ~ 3.5 K). Being formed from the target crystal itself, the ideal contact between the superconductor and the bulk may enable an effective gapping of the Weyl nodes in the bulk because of the proximity effect. Simple ion irradiation may thus serve as a powerful tool for the fabrication of topological quantum devices from monoarsenides, even on an industrial scale.« less

Multiple Quantum Phase Transitions in a two-dimensional superconductor

NASA Astrophysics Data System (ADS)

Bergeal, Nicolas; Biscaras, J.; Hurand, S.; Feuillet-Palma, C.; Lesueur, J.; Budhani, R. C.; Rastogi, A.; Caprara, S.; Grilli, M.

2013-03-01

We studied the magnetic field driven Quantum Phase Transition (QPT) in electrostatically gated superconducting LaTiO3/SrTiO3 interfaces. Through finite size scaling analysis, we showed that it belongs to the (2 +1)D XY model universality class. The system can be described as a disordered array of superconducting islands coupled by a two dimensional electron gas (2DEG). Depending on the 2DEG conductance tuned by the gate voltage, the QPT is single (corresponding to the long range phase coherence in the whole array) or double (one related to local phase coherence, the other one to the array). By retrieving the coherence length critical exponent ν, we showed that the QPT can be ``clean'' or ``dirty'' according to the Harris criteria, depending on whether the phase coherence length is smaller or larger than the island size. The overall behaviour is well described by a model of coupled superconducting puddles in the framework of the fermionic scenario of 2D superconducting QPT.

Ballistic superconductivity in semiconductor nanowires

PubMed Central

Zhang, Hao; Gül, Önder; Conesa-Boj, Sonia; Nowak, Michał P.; Wimmer, Michael; Zuo, Kun; Mourik, Vincent; de Vries, Folkert K.; van Veen, Jasper; de Moor, Michiel W. A.; Bommer, Jouri D. S.; van Woerkom, David J.; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P.A.M.; Quintero-Pérez, Marina; Cassidy, Maja C.; Koelling, Sebastian; Goswami, Srijit; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo P.

2017-01-01

Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor that enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices. PMID:28681843

Enabling Large Focal Plane Arrays Through Mosaic Hybridization

NASA Technical Reports Server (NTRS)

Miller, Timothy M.; Jhabvala, Christine A.; Leong, Edward; Costen, Nick P.; Sharp, Elmer; Adachi, Tomoko; Benford, Dominic J.

2012-01-01

We have demonstrated advances in mosaic hybridization that will enable very large format far-infrared detectors. Specifically we have produced electrical detector models via mosaic hybridization yielding superconducting circuit patbs by hybridizing separately fabricated sub-units onto a single detector unit. The detector model was made on a 100mm diameter wafer while four model readout quadrant chips were made from a separate 100mm wafer. The individually fabric.ted parts were hybridized using a Suss FCI50 flip chip bonder to assemble the detector-readout stack. Once all of the hybridized readouts were in place, a single, large and thick silicon substrate was placed on the stack and attached with permanent epoxy to provide strength and a Coefficient of Thermal Expansion match to the silicon components underneath. Wirebond pads on the readout chips connect circuits to warm readout electronics; and were used to validate the successful superconducting electrical interconnection of the model mosaic-hybrid detector. This demonstration is directly scalable to 150 mm diameter wafers, enabling pixel areas over ten times the area currently available.

Development of a TES-Based Anti-Coincidence Detector for Future X-Ray Observations

NASA Technical Reports Server (NTRS)

Bailey, Catherine N.; Adams, J. S.; Bandler, S. R.; Eckart, M. E.; Ewin, A. J.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S.; Sadleir, J. E.;

Development of a TES-Based Anti-Coincidence Detector for Future X-ray Observatories

NASA Technical Reports Server (NTRS)

Bailey, Catherine

2011-01-01

Microcalorimeters onboard future x-ray observatories require an anti-coincidence detector to remove environmental backgrounds. In order to most effectively integrate this anticoincidence detector with the main microcalorimeter array, both instruments should use similar read-out technology. The detectors used in the Cryogenic Dark Matter Search (CDMS) use a phonon measurement technique that is well suited for an anti-coincidence detector with a microcalorimeter array using SQUID readout. This technique works by using a transition-edge sensor (TES) connected to superconducting collection fins to measure the athermal phonon signal produced when an event occurs in the substrate crystal. Energy from the event propagates through the crystal to the superconducting collection fins, creating quasiparticles, which are then trapped as they enter the TES where they produce a signal. We are currently developing a prototype anti-coincidence detector for future x-ray missions and have recently fabricated test devices with Mo/Au TESs and Al collection fins. We will present results from the first tests of these devices which indicate a proof of concept that quasiparticle trapping is occurring in these materials.

Storing quantum information in spins and high-sensitivity ESR

NASA Astrophysics Data System (ADS)

Morton, John J. L.; Bertet, Patrice

2018-02-01

Quantum information, encoded within the states of quantum systems, represents a novel and rich form of information which has inspired new types of computers and communications systems. Many diverse electron spin systems have been studied with a view to storing quantum information, including molecular radicals, point defects and impurities in inorganic systems, and quantum dots in semiconductor devices. In these systems, spin coherence times can exceed seconds, single spins can be addressed through electrical and optical methods, and new spin systems with advantageous properties continue to be identified. Spin ensembles strongly coupled to microwave resonators can, in principle, be used to store the coherent states of single microwave photons, enabling so-called microwave quantum memories. We discuss key requirements in realising such memories, including considerations for superconducting resonators whose frequency can be tuned onto resonance with the spins. Finally, progress towards microwave quantum memories and other developments in the field of superconducting quantum devices are being used to push the limits of sensitivity of inductively-detected electron spin resonance. The state-of-the-art currently stands at around 65 spins per √{ Hz } , with prospects to scale down to even fewer spins.

Storing quantum information in spins and high-sensitivity ESR.

PubMed

Morton, John J L; Bertet, Patrice

2018-02-01

Quantum information, encoded within the states of quantum systems, represents a novel and rich form of information which has inspired new types of computers and communications systems. Many diverse electron spin systems have been studied with a view to storing quantum information, including molecular radicals, point defects and impurities in inorganic systems, and quantum dots in semiconductor devices. In these systems, spin coherence times can exceed seconds, single spins can be addressed through electrical and optical methods, and new spin systems with advantageous properties continue to be identified. Spin ensembles strongly coupled to microwave resonators can, in principle, be used to store the coherent states of single microwave photons, enabling so-called microwave quantum memories. We discuss key requirements in realising such memories, including considerations for superconducting resonators whose frequency can be tuned onto resonance with the spins. Finally, progress towards microwave quantum memories and other developments in the field of superconducting quantum devices are being used to push the limits of sensitivity of inductively-detected electron spin resonance. The state-of-the-art currently stands at around 65 spins per Hz, with prospects to scale down to even fewer spins. Copyright © 2017. Published by Elsevier Inc.

Quantum Regime of a Two-Dimensional Phonon Cavity

NASA Astrophysics Data System (ADS)

Bolgar, Aleksey N.; Zotova, Julia I.; Kirichenko, Daniil D.; Besedin, Ilia S.; Semenov, Aleksander V.; Shaikhaidarov, Rais S.; Astafiev, Oleg V.

2018-06-01

We realize the quantum regime of a surface acoustic wave (SAW) resonator by demonstrating vacuum Rabi mode splitting due to interaction with a superconducting artificial atom. Reaching the quantum regime is physically difficult and technologically challenging since SAW devices consist of large arrays of narrow metal strips. This work paves the way for realizing analogues of quantum optical phenomena with phonons and can be useful in on-chip quantum electronics.

Superconductivity-induced features in the electronic Raman spectrum of monolayer graphene

NASA Astrophysics Data System (ADS)

García-Ruiz, A.; Mucha-Kruczyński, M.; Fal'ko, V. I.

2018-04-01

Using the continuum model, we investigate theoretically the contribution of the low-energy electronic excitations to the Raman spectrum of superconducting monolayer graphene. We consider superconducting phases characterised by an isotropic order parameter in a single valley and find a Raman peak at a shift set by the size of the superconducting gap. The height of this peak is proportional to the square root of the gap and the third power of the Fermi level, and we estimate its quantum efficiency as I ˜10-14 .

Coupling a single nitrogen-vacancy center with a superconducting qubit via the electro-optic effect

NASA Astrophysics Data System (ADS)

Li, Chang-Hao; Li, Peng-Bo

2018-05-01

We propose an efficient scheme for transferring quantum states and generating entangled states between two qubits of different nature. The hybrid system consists of a single nitrogen-vacancy (NV) center and a superconducting (SC) qubit, which couple to an optical cavity and a microwave resonator, respectively. Meanwhile, the optical cavity and the microwave resonator are coupled via the electro-optic effect. By adjusting the relative parameters, we can achieve high-fidelity quantum state transfer as well as highly entangled states between the NV center and the SC qubit. This protocol is within the reach of currently available techniques, and may provide interesting applications in quantum communication and computation with single NV centers and SC qubits.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Efficient One-Step Generation of Cluster State with Charge Qubits in Circuit QED

NASA Astrophysics Data System (ADS)

Wang, Yi-Min; Li, Cheng-Zu

2010-01-01

We propose theoretical schemes to generate highly entangled cluster state with superconducting qubits in a circuit QED architecture. Charge qubits are located inside a superconducting transmission line, which serves as a quantum data bus. We show that large clusters state can be efficiently generated in just one step with the long-range Ising-like unitary operators. The quantum operations which are generally realized by two coupling mechanisms: either voltage coupling or current coupling, depend only on global geometric features and are insensitive not only to the thermal state of the transmission line but also to certain random operation errors. Thus high-fidelity one-way quantum computation can be achieved.

Beyond the Fermi liquid paradigm: Hidden Fermi liquids

PubMed Central

Jain, J. K.; Anderson, P. W.

2009-01-01

An intense investigation of possible non-Fermi liquid states of matter has been inspired by two of the most intriguing phenomena discovered in the past quarter century, namely, high-temperature superconductivity and the fractional quantum Hall effect. Despite enormous conceptual strides, these two fields have developed largely along separate paths. Two widely employed theories are the resonating valence bond theory for high-temperature superconductivity and the composite fermion theory for the fractional quantum Hall effect. The goal of this perspective article is to note that they subscribe to a common underlying paradigm: They both connect these exotic quantum liquids to certain ordinary Fermi liquids residing in unphysical Hilbert spaces. Such a relation yields numerous nontrivial experimental consequences, exposing these theories to rigorous and definitive tests. PMID:19506260

Fidelity Study of Superconductivity in Extended Hubbard Models

NASA Astrophysics Data System (ADS)

Plonka, Nachum; Jia, Chunjing; Moritz, Brian; Wang, Yao; Devereaux, Thomas

2015-03-01

The role of strong electronic correlations on unconventional superconductivity remains an important open question. Here, we explore the influence of long-range Coulomb interactions, present in real material systems, through nearest and next-nearest neighbor extended Hubbard interactions in addition to the usual on-site terms. Utilizing large scale, numerical exact diagonalization, we analyze the signatures of superconductivity in the ground states through the fidelity metric of quantum information theory. We find that these extended interactions enhance charge fluctuations with various wave vectors. These suppress superconductivity in general, but in certain parameter regimes superconductivity is sustained. This has implications for tuning extended interactions in real materials.

Demonstration of quantum superiority in learning parity with noise with superconducting qubits

NASA Astrophysics Data System (ADS)

Ristè, Diego; da Silva, Marcus; Ryan, Colm; Cross, Andrew; Smolin, John; Gambetta, Jay; Chow, Jerry; Johnson, Blake

A problem in machine learning is to identify the function programmed in an unknown device, or oracle, having only access to its output. In particular, a parity function computes the parity of a subset of a bit register. We implement an oracle executing parity functions in a five-qubit superconducting processor and compare the performance of a classical and a quantum learner. The classical learner reads the output of multiple oracle calls and uses the results to infer the hidden function. In addition to querying the oracle, the quantum learner can apply coherent rotations on the output register before the readout. We show that, given a target success probability, the quantum approach outperforms the classical one in the number of queries needed. Moreover, this gap increases with readout noise and with the size of the qubit register. This result shows that quantum advantage can already emerge in current systems with a few, noisy qubits. We acknowledge support from IARPA under Contract W911NF-10-1-0324.