Science.gov

Sample records for flux quantum pulses

  1. Design and Operation of a 9-bit Single-flux-quantum Pulse-frequency Modulation Digital-to-analog Converter

    NASA Astrophysics Data System (ADS)

    Mizugaki, Yoshinao; Takahashi, Yoshitaka; Shimada, Hiroshi; Maezawa, Masaaki

    We designed and operated a 9-bit single-flux-quantum (SFQ) digital-to-analog converter (DAC). SFQ pulse-frequency modulation (PFM) was employed for generation of variable quantum output voltage, where a 9-bit variable pulse number multiplier and a 100-fold voltage multiplier were the key components. Test chips were fabricated using a Nb Josephson integration technology. Arbitrary voltage waveforms were synthesized with the maximum voltage of 2.54 mV. For ac voltage standard applications, relationships between the DAC resolution and the synthesized waveform frequency are discussed.

  2. Pulsed quantum optomechanics

    PubMed Central

    Vanner, M. R.; Pikovski, I.; Cole, G. D.; Kim, M. S.; Brukner, Č.; Hammerer, K.; Milburn, G. J.; Aspelmeyer, M.

    2011-01-01

    Studying mechanical resonators via radiation pressure offers a rich avenue for the exploration of quantum mechanical behavior in a macroscopic regime. However, quantum state preparation and especially quantum state reconstruction of mechanical oscillators remains a significant challenge. Here we propose a scheme to realize quantum state tomography, squeezing, and state purification of a mechanical resonator using short optical pulses. The scheme presented allows observation of mechanical quantum features despite preparation from a thermal state and is shown to be experimentally feasible using optical microcavities. Our framework thus provides a promising means to explore the quantum nature of massive mechanical oscillators and can be applied to other systems such as trapped ions. PMID:21900608

  3. Pulse power applications of flux compression generators

    NASA Astrophysics Data System (ADS)

    Fowler, C. M.; Caird, R. S.; Erickson, D. J.; Freeman, B. L.

    Characteristics are presented for two different types of explosive driven flux compression generators and a megavolt pulse transformer. Status reports are given for rail gun and plasma focus programs for which the generators serve as power sources.

  4. Annihilation of Quantum Magnetic Fluxes

    NASA Astrophysics Data System (ADS)

    Gonzalez, W. D.

    After introducing the concepts associated with the Aharonov and Bohm effect and with the existence of a quantum of magnetic flux (QMF), we briefly discuss the Ginzburg-Landau theory that explains its origin and fundamental consequences. Also relevant observations of QMFs obtained in the laboratory using superconducting systems (vortices) are mentioned. Next, we describe processes related with the interaction of QMFs with opposite directions in terms of the gauge field geometry related to the vector potential. Then, we discuss the use of a Lagrangian density for a scalar field theory involving radiation in order to describe the annihilation of QMFs, claimed to be responsible for the emission of photons with energies corresponding to that of the annihilated magnetic fields. Finally, a possible application of these concepts to the observed variable dynamics of neutron stars is briefly mentioned.

  5. Coherent pulse position modulation quantum cipher

    SciTech Connect

    Sohma, Masaki; Hirota, Osamu

    2014-12-04

    On the basis of fundamental idea of Yuen, we present a new type of quantum random cipher, where pulse position modulated signals are encrypted in the picture of quantum Gaussian wave form. We discuss the security of our proposed system with a phase mask encryption.

  6. Flux Exclusion Superconducting Quantum Metamaterial: Towards Quantum-level Switching

    PubMed Central

    Savinov, V.; Tsiatmas, A.; Buckingham, A. R.; Fedotov, V. A.; de Groot, P. A. J.; Zheludev, N. I.

    2012-01-01

    Nonlinear and switchable metamaterials achieved by artificial structuring on the subwavelength scale have become a central topic in photonics research. Switching with only a few quanta of excitation per metamolecule, metamaterial's elementary building block, is the ultimate goal, achieving which will open new opportunities for energy efficient signal handling and quantum information processing. Recently, arrays of Josephson junction devices have been proposed as a possible solution. However, they require extremely high levels of nanofabrication. Here we introduce a new quantum superconducting metamaterial which exploits the magnetic flux quantization for switching. It does not contain Josephson junctions, making it simple to fabricate and scale into large arrays. The metamaterial was manufactured from a high-temperature superconductor and characterized in the low intensity regime, providing the first observation of the quantum phenomenon of flux exclusion affecting the far-field electromagnetic properties of the metamaterial. PMID:22690319

  7. Quantum state engineering with flux-biased Josephson phase qubits by rapid adiabatic passages

    SciTech Connect

    Nie, W.; Huang, J. S.; Shi, X.; Wei, L. F.

    2010-09-15

    In this article, the scheme of quantum computing based on the Stark-chirped rapid adiabatic passage (SCRAP) technique [L. F. Wei, J. R. Johansson, L. X. Cen, S. Ashhab, and F. Nori, Phys. Rev. Lett. 100, 113601 (2008)] is extensively applied to implement quantum state manipulations in flux-biased Josephson phase qubits. The broken-parity symmetries of bound states in flux-biased Josephson junctions are utilized to conveniently generate the desirable Stark shifts. Then, assisted by various transition pulses, universal quantum logic gates as well as arbitrary quantum state preparations can be implemented. Compared with the usual {pi}-pulse operations widely used in experiments, the adiabatic population passages proposed here are insensitive to the details of the applied pulses and thus the desirable population transfers can be satisfyingly implemented. The experimental feasibility of the proposal is also discussed.

  8. Development of Integrated Single Flux Quantum - Superconducting Qubit Circuits

    NASA Astrophysics Data System (ADS)

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

    Significant theoretical and experimental progress has been made in recent years towards a scalable superconducting quantum circuit architecture. Here we present a first attempt to integrate classical control elements from the single flux quantum (SFQ) digital logic family with a superconducting transom qubit on a single chip. The SFQ driving circuit is fabricated in a six-layer high-Jc Nb/Al-AlOx/Nb junction process while the transmon qubit is subsequently formed using submicron Al-AlOx-Al junctions grown by double-angle evaporation. We investigate sources of decoherence associated with the more complex fabrication process and describe first attempts to perform coherent qubit manipulations using resonant trains of SFQ pulses.

  9. Local flux intrusion in HTS annuli during pulsed field magnetization

    NASA Astrophysics Data System (ADS)

    Korotkov, V. S.; Krasnoperov, E. P.; Kartamyshev, A. A.

    2016-03-01

    During pulsed field magnetization of melt-grown HTS flux jumps can occur and the shielding current falls by 10-20 times. As the duration of pulse is shorter than the temperature relaxation time (<< 1 s), the circular current remains small during the field falling. The residual trapped field in the hole of the annulus has a direction opposite to that of the pulsed field. Small circular current and high critical current density are explained by the fact that flux moves through narrow regions of the annulus body. The angle of the sector with “soft flux” (i.e. a low Jc region) is estimated to be ∼ 7 deg.

  10. Continuous and Pulsed Quantum Zeno Effect

    SciTech Connect

    Streed, Erik W.; Mun, Jongchul; Boyd, Micah; Campbell, Gretchen K.; Medley, Patrick; Ketterle, Wolfgang; Pritchard, David E.

    2006-12-31

    Continuous and pulsed quantum Zeno effects were observed using a {sup 87}Rb Bose-Einstein condensate. Oscillations between two ground hyperfine states of a magnetically trapped condensate, externally driven at a transition rate {omega}{sub R}, were suppressed by destructively measuring the population in one of the states with resonant light. The suppression of the transition rate in the two-level system was quantified for pulsed measurements with a time interval {delta}t between pulses and continuous measurements with a scattering rate {gamma}. We observe that the continuous measurements exhibit the same suppression in the transition rate as the pulsed measurements when {gamma}{delta}t=3.60(0.43), in agreement with the predicted value of 4. Increasing the measurement rate suppressed the transition rate down to 0.005{omega}{sub R}.

  11. Quantum transport in coupled resonators enclosed synthetic magnetic flux

    NASA Astrophysics Data System (ADS)

    Jin, L.

    2016-07-01

    Quantum transport properties are instrumental to understanding quantum coherent transport processes. Potential applications of quantum transport are widespread, in areas ranging from quantum information science to quantum engineering, and not restricted to quantum state transfer, control and manipulation. Here, we study light transport in a ring array of coupled resonators enclosed synthetic magnetic flux. The ring configuration, with an arbitrary number of resonators embedded, forms a two-arm Aharonov-Bohm interferometer. The influence of magnetic flux on light transport is investigated. Tuning the magnetic flux can lead to resonant transmission, while half-integer magnetic flux quantum leads to completely destructive interference and transmission zeros in an interferometer with two equal arms.

  12. Flux sensitivity of quantum spin Hall rings

    NASA Astrophysics Data System (ADS)

    Crépin, F.; Trauzettel, B.

    2016-01-01

    We analyze the periodicity of persistent currents in quantum spin Hall loops, partly covered with an s-wave superconductor, in the presence of a flux tube. Much like in normal (non-helical) metals, the periodicity of the single-particle spectrum goes from Φ0 = h / e to Φ0 / 2 as the length of the superconductor is increased past the coherence length of the superconductor. We further analyze the periodicity of the persistent current, which is a many-body effect. Interestingly, time reversal symmetry and parity conservation can significantly change the period. We find a 2Φ0-periodic persistent current in two distinct regimes, where one corresponds to a Josephson junction and the other one to an Aharonov-Bohm setup.

  13. Effect of various pulse wave forms for pulse-type magnetic flux pump

    NASA Astrophysics Data System (ADS)

    Bai, Zhiming; Chen, Chuan; Wu, Yanqing; Zhen, Zhen

    2011-09-01

    The excitation current of magnetic pole windings in magnetic flux pump needs to be generated by a control system. In this paper, the control system of pulse-type high temperature superconducting magnetic flux pump is discussed in detail. The control system consists of a control circuit and a drive circuit. A direct current power supply is the unique power supply of the drive circuit. The control circuit is powered by a computer through a USB interface of the computer. The control circuit receives commands from the computer and controls the drive circuit to generate different pulse waves. Each pulse wave generates a unique pulse-type traveling magnetic field and will pump magnetic flux into the superconducting loop. Experiments have been performed to examine the pumping effect of different pulse waves on both MgB 2 and Bi-2223 superconducting loops using the proposed control system, and the best pulse wave has been found. The experimental results show that the magnetic flux pump can compensate current decay up to 32.5 A for MgB 2 loop and 129 A for Bi-2223 loop. It indicates that the control system of the pulse-type magnetic flux pump is effective and feasible.

  14. Blind Quantum Computing with Weak Coherent Pulses

    NASA Astrophysics Data System (ADS)

    Dunjko, Vedran; Kashefi, Elham; Leverrier, Anthony

    2012-05-01

    The universal blind quantum computation (UBQC) protocol [A. Broadbent, J. Fitzsimons, and E. Kashefi, in Proceedings of the 50th Annual IEEE Symposiumon Foundations of Computer Science (IEEE Computer Society, Los Alamitos, CA, USA, 2009), pp. 517-526.] allows a client to perform quantum computation on a remote server. In an ideal setting, perfect privacy is guaranteed if the client is capable of producing specific, randomly chosen single qubit states. While from a theoretical point of view, this may constitute the lowest possible quantum requirement, from a pragmatic point of view, generation of such states to be sent along long distances can never be achieved perfectly. We introduce the concept of ɛ blindness for UBQC, in analogy to the concept of ɛ security developed for other cryptographic protocols, allowing us to characterize the robustness and security properties of the protocol under possible imperfections. We also present a remote blind single qubit preparation protocol with weak coherent pulses for the client to prepare, in a delegated fashion, quantum states arbitrarily close to perfect random single qubit states. This allows us to efficiently achieve ɛ-blind UBQC for any ɛ>0, even if the channel between the client and the server is arbitrarily lossy.

  15. Correlated states of a quantum oscillator acted by short pulses

    NASA Technical Reports Server (NTRS)

    Manko, O. V.

    1993-01-01

    Correlated squeezed states for a quantum oscillator are constructed based on the method of quantum integrals of motion. The quantum oscillator is acted upon by short duration pulses. Three delta-kickings of frequency are used to model the pulses' dependence upon the time aspects of the frequency of the oscillator. Additionally, the correlation coefficient and quantum variances of operations of coordinates and momenta are written in explicit form.

  16. Quantum nondemolition measurement by pulsed oscillation

    NASA Astrophysics Data System (ADS)

    Zhang, Gui-Ying; Zhao, Kai-Feng

    2016-03-01

    Paramagnetic Faraday rotation is a quantum nondemolition measurement method that can generate spin squeezing and improve the measurement precision of a collective spin component beyond the standard quantum limit. In practice, a constant bias magnetic field is used to drive the spin precessing at sufficiently high frequency in order to lift the signal out of low-frequency technical noises. However, continuous measurement of precessing spins introduces back-action noise (BAN) due to the light-shift effect. Two types of back-action-evading (BAE) measurement of collective spin components have been demonstrated recently: continuous measurement of a two-ensemble system and stroboscopic measurement of a single ensemble. Here we propose another single ensemble BAE measurement by periodically modulating the bias field with π pulses. Our theoretical calculation shows that under experimental settings where pulse-field modulation does not introduce significant decoherences, the proposed method can suppress the BAN and generate spin squeezing faster than the stroboscopic one at the same probe light power. Moreover, if it is combined with synchronous stroboscopic probing, light-shift BAN can be completely eliminated.

  17. Quantum depinning of flux lines from columnar defects

    SciTech Connect

    Chudnovsky, E.M. ); Ferrera, A.; Vilenkin, A. )

    1995-01-01

    The depinning of a flux line from a columnar defect is studied within the path-integral approach. Instantons of the quantum field theory in 1+1 dimensions are computed for the flux line whose dynamics is dominated by the Magnus force. The universal temperature dependence of the decay rate in the proximity of the critical current is obtained. This problem provides an example of macroscopic quantum tunneling, which is accessible to the direct comparison between theory and experiment.

  18. Effect of pulse frequency on the ion fluxes during pulsed dc magnetron sputtering

    SciTech Connect

    Rahamathunnisa, M.; Cameron, D. C.

    2009-03-15

    The ion fluxes and energies which impinge on the substrate during the deposition of chromium nitride by asymmetric bipolar pulsed dc reactive magnetron sputtering have been analyzed using energy resolved mass spectrometry. It has been found that there is a remarkable increase in ion flux at higher pulse frequencies and that the peak ion energy is directly related to the positive voltage overshoot of the target voltage. The magnitude of the metal flux depositing on the substrate is consistent with a 'dead time' of {approx}0.7 {mu}s at the start of the on period. The variation of the ion flux with pulse frequency has been explained by a simple model in which the ion density during the on period has a large peak which is slightly delayed from the large negative voltage overshoot which occurs at the start of the on pulse due to increased ionization at that time. This is consistent with the previously observed phenomena in pulsed sputtering.

  19. Developing a High-Flux Isolated Attosecond Pulse Source

    NASA Astrophysics Data System (ADS)

    Kamalov, Andrei; Ware, Matthew; Bucksbaum, Philip; Cryan, James

    2016-05-01

    High harmonic based light sources have proven to be valuable experimental tools that facilitate studies of electron dynamics at their natural timescale, the attosecond regime. The nature of driving laser sources used in high harmonic generation make it difficult to attain attosecond pulses that are both isolated in time and of a high intensity. We present our progress in commissioning a beamline designed to produce high-flux isolated attosecond pulses. A multistep amplification process provides us with 30 mJ, 25 fs pulses centered around 800 nm with 100 Hz repetition rate. These pulses are spatially split and focused into a gas cell. A non-collinear optical gating scheme is used to produce a lighthouse source of high harmonic radiation wherein each beamlet is an isolated attosecond pulse. A variable-depth grazing-incidence stepped mirror is fabricated to extend the optical path length of the older beamlets and thus overlap the beamlets in time. The combined beam is tightly focused and ensuing mechanics will be studied with an electron spectrometer as well as a xuv photon spectrometer. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division.

  20. Extending quantum coherence of superconducting flux

    NASA Astrophysics Data System (ADS)

    Yan, Fei; Kamal, Archana; Orlando, Terry; Gustavsson, Simon; Oliver, William; Engineering Quantum Systems, MIT Team

    We present the design of a superconducting qubit with multiple Josephson junctions. The design starts with a capacitively shunted flux qubit, and it incorporates particular junction parameter choices for the purpose of simultaneously optimizing over transition frequency, anharmonicity, flux- and charge-noise sensitivity around flux degeneracy. By studying the scaling properties with design parameters, we identify directions to extend coherence substantially. This research was funded by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA) via MIT Lincoln Laboratory under Air Force Contract No. FA8721-05-C-0002.

  1. Adiabatic quantum computing with phase modulated laser pulses

    PubMed Central

    Goswami, Debabrata

    2005-01-01

    Implementation of quantum logical gates for multilevel systems is demonstrated through decoherence control under the quantum adiabatic method using simple phase modulated laser pulses. We make use of selective population inversion and Hamiltonian evolution with time to achieve such goals robustly instead of the standard unitary transformation language. PMID:17195865

  2. Comment on 'Realism and quantum flux tunneling'

    NASA Technical Reports Server (NTRS)

    Leggett, A. J.; Garg, Anupam

    1987-01-01

    A reply is presented to Ballentine's (1987) critique of the Legett and Garg (1985) experiment to discriminate between the experimental predictions of quantum mechanics (QM) and those of a class of macrorealistic theories. Legett and Garg uphold their earlier conclusions on the basis of the fact that the present critique refers to an experiment which was not in fact proposed. It is stressed that the original work involved an analysis according to macrorealism, while the calculations of Ballentine only demonstrate the internal consistency of the formalism of QM when applied to three consecutive actually performed experiments.

  3. Design and Operation of 1000-fold Voltage Multiplier based on Double-flux-quantum Amplifier

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Moriya, M.; Shimada, H.; Mizugaki, Y.; Maezawa, M.

    Rapid-single-flux-quantum digital-to-analogue converters (RSFQ-DACs) are now under development for ac voltage standard applications. The voltage multiplier (VM), which precisely amplifies the input voltage, is a key component for RSFQ-DACs. Because the amount of bias current for a conventional VM increases in proportion to its multiplication factor, we have been looking for a VM device which is operated on a different principle. In this paper, we report our design of a 1000-fold VM comprising double flux quantum amplifiers (DFQAs) of which the amount of bias current is independent of its multiplication factor. Test circuits were fabricated using a 2.5 kA/cm2 Nb process. We confirm that the experimental results demonstrate the 1000-fold operation up to 13.2 GHz input SFQ pulse repetition frequency.

  4. Optimized pulse sequences for suppressing unwanted transitions in quantum systems

    SciTech Connect

    Schroeder, C. A.; Agarwal, G. S.

    2011-01-15

    We investigate the nature of the pulse sequence so that unwanted transitions in quantum systems can be inhibited optimally. For this purpose we show that the sequence of pulses proposed by Uhrig [Phys. Rev. Lett. 98, 100504 (2007)] in the context of inhibition of environmental dephasing effects is optimal. We derive exact results for inhibiting the transitions and confirm the results numerically. We posit a very significant improvement by usage of the Uhrig sequence over an equidistant sequence in decoupling a quantum system from unwanted transitions. The physics of inhibition is the destructive interference between transition amplitudes before and after each pulse.

  5. Experimental quantum fingerprinting with weak coherent pulses

    NASA Astrophysics Data System (ADS)

    Xu, Feihu; Arrazola, Juan Miguel; Wei, Kejin; Wang, Wenyuan; Palacios-Avila, Pablo; Feng, Chen; Sajeed, Shihan; Lütkenhaus, Norbert; Lo, Hoi-Kwong

    2015-10-01

    Quantum communication holds the promise of creating disruptive technologies that will play an essential role in future communication networks. For example, the study of quantum communication complexity has shown that quantum communication allows exponential reductions in the information that must be transmitted to solve distributed computational tasks. Recently, protocols that realize this advantage using optical implementations have been proposed. Here we report a proof-of-concept experimental demonstration of a quantum fingerprinting system that is capable of transmitting less information than the best-known classical protocol. Our implementation is based on a modified version of a commercial quantum key distribution system using off-the-shelf optical components over telecom wavelengths, and is practical for messages as large as 100 Mbits, even in the presence of experimental imperfections. Our results provide a first step in the development of experimental quantum communication complexity.

  6. Experimental quantum fingerprinting with weak coherent pulses.

    PubMed

    Xu, Feihu; Arrazola, Juan Miguel; Wei, Kejin; Wang, Wenyuan; Palacios-Avila, Pablo; Feng, Chen; Sajeed, Shihan; Lütkenhaus, Norbert; Lo, Hoi-Kwong

    2015-01-01

    Quantum communication holds the promise of creating disruptive technologies that will play an essential role in future communication networks. For example, the study of quantum communication complexity has shown that quantum communication allows exponential reductions in the information that must be transmitted to solve distributed computational tasks. Recently, protocols that realize this advantage using optical implementations have been proposed. Here we report a proof-of-concept experimental demonstration of a quantum fingerprinting system that is capable of transmitting less information than the best-known classical protocol. Our implementation is based on a modified version of a commercial quantum key distribution system using off-the-shelf optical components over telecom wavelengths, and is practical for messages as large as 100 Mbits, even in the presence of experimental imperfections. Our results provide a first step in the development of experimental quantum communication complexity. PMID:26515586

  7. Experimental quantum fingerprinting with weak coherent pulses

    PubMed Central

    Xu, Feihu; Arrazola, Juan Miguel; Wei, Kejin; Wang, Wenyuan; Palacios-Avila, Pablo; Feng, Chen; Sajeed, Shihan; Lütkenhaus, Norbert; Lo, Hoi-Kwong

    2015-01-01

    Quantum communication holds the promise of creating disruptive technologies that will play an essential role in future communication networks. For example, the study of quantum communication complexity has shown that quantum communication allows exponential reductions in the information that must be transmitted to solve distributed computational tasks. Recently, protocols that realize this advantage using optical implementations have been proposed. Here we report a proof-of-concept experimental demonstration of a quantum fingerprinting system that is capable of transmitting less information than the best-known classical protocol. Our implementation is based on a modified version of a commercial quantum key distribution system using off-the-shelf optical components over telecom wavelengths, and is practical for messages as large as 100 Mbits, even in the presence of experimental imperfections. Our results provide a first step in the development of experimental quantum communication complexity. PMID:26515586

  8. Magnetic Flux Compression Concept for Nuclear Pulse Propulsion and Power

    NASA Technical Reports Server (NTRS)

    Litchford, Ronald J.

    2000-01-01

    The desire for fast, efficient interplanetary transport requires propulsion systems having short acceleration times and very high specific impulse attributes. Unfortunately, most highly efficient propulsion systems which are within the capabilities of present day technologies are either very heavy or yield very low impulse such that the acceleration time to final velocity is too long to be of lasting interest, One exception, the nuclear thermal thruster, could achieve the desired acceleration but it would require inordinately large mass ratios to reach the range of desired final velocities. An alternative approach, among several competing concepts that are beyond our modern technical capabilities, is a pulsed thermonuclear device utilizing microfusion detonations. In this paper, we examine the feasibility of an innovative magnetic flux compression concept for utilizing microfusion detonations, assuming that such low yield nuclear bursts can be realized in practice. In this concept, a magnetic field is compressed between an expanding detonation driven diamagnetic plasma and a stationary structure formed from a high temperature superconductor (HTSC). In general, we are interested in accomplishing two important functions: (1) collimation of a hot diamagnetic plasma for direct thrust production; and (2) pulse power generation for dense plasma ignition. For the purposes of this research, it is assumed that rnicrofusion detonation technology may become available within a few decades, and that this approach could capitalize on recent advances in inertial confinement fusion ICF) technologies including magnetized target concepts and antimatter initiated nuclear detonations. The charged particle expansion velocity in these detonations can be on the order of 10 (exp 6)- 10 (exp 7) meters per second, and, if effectively collimated by a magnetic nozzle, can yield the Isp and the acceleration levels needed for practical interplanetary spaceflight. The ability to ignite pure

  9. Bosonic Integer Quantum Hall Effect in Optical Flux Lattices

    NASA Astrophysics Data System (ADS)

    Sterdyniak, A.; Cooper, Nigel R.; Regnault, N.

    2015-09-01

    In two dimensions strongly interacting bosons in a magnetic field can realize a bosonic integer quantum Hall state, the simplest two-dimensional example of a symmetry-protected topological phase. We propose a realistic implementation of this phase using an optical flux lattice. Through exact diagonalization calculations, we show that the system exhibits a clear bulk gap and the topological signature of the bosonic integer quantum Hall state. In particular, the calculation of the many-body Chern number leads to a quantized Hall conductance in agreement with the analytical predictions. We also study the stability of the phase with respect to some of the experimentally relevant parameters.

  10. Coplanar waveguide flux qubit suitable for quantum annealing

    NASA Astrophysics Data System (ADS)

    Quintana, Chris; Chen, Yu; Sank, D.; Kafri, D.; Megrant, A.; White, T. C.; Shabani, A.; Barends, R.; Campbell, B.; Chen, Z.; Chiaro, B.; Dunsworth, A.; Fowler, A.; Jeffrey, E.; Kelly, J.; Lucero, E.; Mutus, J. Y.; Neeley, M.; Neill, C.; O'Malley, P. J. J.; Roushan, P.; Vainsencher, A.; Wenner, J.; Martinis, J. M.

    We introduce the ''fluxmon'' flux qubit, designed with the goal of practical quantum annealing. The qubit's capacitance and linear inductance are provided by a coplanar waveguide on a low loss substrate, minimizing dielectric dissipation and in principle allowing for GHz-scale inter-qubit coupling in a highly connected tunable architecture. Utilizing a dispersive microwave readout scheme, we characterize single-qubit noise and dissipation, and present a simple tunable inter-qubit coupler. We discuss tradeoffs between coherence and coupling in a quantum annealing architecture. This work was supported by Google Inc. and by the NSF GRFP.

  11. Controlling Ion and UV/VUV Photon Fluxes in Pulsed Low Pressure Plasmas for Materials Processing

    NASA Astrophysics Data System (ADS)

    Tian, Peng; Kushner, Mark J.

    2012-10-01

    UV/VUV photon fluxes in plasma materials processing have a variety of effects ranging from damaging to synergistic. To optimize these processes, it is desirable to have separate control over the fluxes of ions and photons, or at least be able to control their relative fluxes or overlap in time. Pulsed plasmas may provide such control as the rates at which ion and photon fluxes respond to the pulse power deposition are different. Results from a computational investigation of pulsed plasmas will be discussed to determine methods to control the ratio of ion to photon fluxes. Simulations were performed using a 2-dimensional plasma hydrodynamics model which addresses radiation transport using a Monte Carlo Simulation. Radiation transport is frequency resolved using partial-frequency-redistribution algorithms. Results for low pressure (10s of mTorr) inductively and capacitively coupled plasmas in Ar/Cl2 mixtures will be discussed while varying duty cycle, reactor geometry, gas mixture and pressure. We found that the time averaged ratio of VUV photon-to-ion fluxes in ICPs can be controlled with duty cycle of the pulsed power. Even with radiation trapping, photon fluxes tend to follow the power pulse whereas due to their finite response times, fluxes of ions tend to average the power pulse. Due to the overshoot in electron temperature that occurs at the start of low-duty-cycle pulses, disproportionately large photon fluxes (compared to ion fluxes) can be generated.

  12. Novel latch for adiabatic quantum-flux-parametron logic

    SciTech Connect

    Takeuchi, Naoki Yamanashi, Yuki; Yoshikawa, Nobuyuki; Ortlepp, Thomas

    2014-03-14

    We herein propose the quantum-flux-latch (QFL) as a novel latch for adiabatic quantum-flux-parametron (AQFP) logic. A QFL is very compact and compatible with AQFP logic gates and can be read out in one clock cycle. Simulation results revealed that the QFL operates at 5 GHz with wide parameter margins of more than ±22%. The calculated energy dissipation was only ∼0.1 aJ/bit, which yields a small energy delay product of 20 aJ·ps. We also designed shift registers using QFLs to demonstrate more complex circuits with QFLs. Finally, we experimentally demonstrated correct operations of the QFL and a 1-bit shift register (a D flip-flop)

  13. Storage and retrieval of light pulse in coupled quantum wells

    NASA Astrophysics Data System (ADS)

    Liu, Jibing; Liu, Na; Shan, Chuanjia; Li, Hong; Liu, Tangkun; Zheng, Anshou

    2016-03-01

    In this paper, we propose an effective scheme to create a frequency entangled states based on bound-to-bound inter-subband transitions in an asymmetric three-coupled quantum well structure. A four-subband cascade configuration quantum well structure is illuminated with a pulsed probe field and two continuous wave control laser fields to generate a mixing field. By properly adjusting the frequency detunings and the intensity of coupling fields, the conversion efficiency can reach 100%. A maximum entangled state can be achieved by selecting a proper length of the sample. We also numerically investigate the propagation dynamics of the probe pulse and mixing pulse, the results show that two frequency components are able to exchange energy through a four-wave mixing process. Moreover, by considering special coupling fields, the storage and retrieval of the probe pulse is also numerically simulated.

  14. Multifrequency control pulses for multilevel superconducting quantum circuits

    SciTech Connect

    Forney, Anne M.; Jackson, Steven R.; Strauch, Frederick W.

    2010-01-15

    Superconducting quantum circuits, such as the superconducting phase qubit, have multiple quantum states that can interfere with ideal qubit operation. The use of multiple frequency control pulses, resonant with the energy differences of the multistate system, is theoretically explored. An analytical method to design such control pulses is developed, using a generalization of the Floquet method to multiple frequency controls. This method is applicable to optimizing the control of both superconducting qubits and qudits and is found to be in excellent agreement with time-dependent numerical simulations.

  15. Design of a Pulsed Flux Concentrator for the ILC Positron Source

    SciTech Connect

    Gronberg, J; Abbott, R; Brown, C; Javedani, J; Piggott, W T; Clarke, J

    2010-05-17

    The Positron Source for the International Linear Collider requires an optical matching device after the target to increase the capture efficiency for positrons. Pulsed flux concentrators have been used by previous machines to improve the capture efficiency but the ILC has a 1 ms long pulse train which is too long for a standard flux concentrator. A pulsed flux concentrator with a 40 ms flat top was created for a hyperon experiment in 1965 which used liquid nitrogen cooling to reduce the resistance of the concentrating plates and extend the lifetime of the pulse. We report on a design for a 1 ms device based on this concept.

  16. Pulse-Gated Quantum-Dot Hybrid Qubit

    NASA Astrophysics Data System (ADS)

    Koh, Teck Seng; Gamble, John King; Friesen, Mark; Eriksson, M. A.; Coppersmith, S. N.

    2012-12-01

    A quantum-dot hybrid qubit formed from three electrons in a double quantum dot has the potential for great speed, due to the presence of level crossings where the qubit becomes chargelike. Here, we show how to exploit the level crossings to implement fast pulsed gating. We develop one- and two-qubit dc quantum gates that are simpler than the previously proposed ac gates. We obtain closed-form solutions for the control sequences and show that the gates are fast (subnanosecond) and can achieve high fidelities.

  17. Rapid single flux quantum digital-to-analog converter for ac voltage standard

    NASA Astrophysics Data System (ADS)

    Maezawa, Masaaki; Hirayama, Fuminori; Suzuki, Motohiro

    2005-10-01

    A digital-to-analog (D/A) converter based on rapid single flux quantum (RSFQ) circuits is a potential device for establishing a new generation of ac voltage standards. We are developing RSFQ D/A converters that can generate an ac waveform with an accurately defined rms value. Our goal in the near future is the synthesis of an ac waveform with a 100-mV peak voltage that will allow accurate characterization of the thermal voltage converters currently used for setting ac-dc transfer standards. We have designed, fabricated and successfully tested key subsystems of the RSFQ D/A converter including a 10-stage pulse-number multiplier, a 1-bit slice of a pulse distributor and a 9.5-bit voltage multiplier.

  18. Noncollinear gating for high-flux isolated-attosecond-pulse generation

    NASA Astrophysics Data System (ADS)

    Zhong, Shiyang; He, Xinkui; Jiang, Yujiao; Teng, Hao; He, Peng; Liu, Yangyang; Zhao, Kun; Wei, Zhiyi

    2016-03-01

    We propose an approach for producing high-flux isolated-attosecond pulses (IAPs) based on noncollinear geometry of high-order harmonic generation (HHG). By combining a main driving pulse and an ultrashort gating pulse in the interaction medium to form a tilt wave front in a very narrow overlapping time region, the attosecond pulses generated in this region are spatially separated from the original beam in the far field. It gives a way of extracting IAPs as well as fully characterizing an attosecond-pulse train (APT). Since this approach set no restriction on the pulse duration of the main driving pulse, it is particularly suitable for high-flux IAP generation by a high-energy laser which usually has multicycle pulse duration.

  19. Ion flux and ion distribution function measurements in synchronously pulsed inductively coupled plasmas

    SciTech Connect

    Brihoum, Melisa; Cunge, Gilles; Darnon, Maxime; Joubert, Olivier; Gahan, David; Braithwaite, Nicholas St. J.

    2013-03-15

    Changes in the ion flux and the time-averaged ion distribution functions are reported for pulsed, inductively coupled RF plasmas (ICPs) operated over a range of duty cycles. For helium and argon plasmas, the ion flux increases rapidly after the start of the RF pulse and after about 50 {mu}s reaches the same steady state value as that in continuous ICPs. Therefore, when the plasma is pulsed at 1 kHz, the ion flux during the pulse has a value that is almost independent of the duty cycle. By contrast, in molecular electronegative chlorine/chlorosilane plasmas, the ion flux during the pulse reaches a steady state value that depends strongly on the duty cycle. This is because both the plasma chemistry and the electronegativity depend on the duty cycle. As a result, the ion flux is 15 times smaller in a pulsed 10% duty cycle plasma than in the continuous wave (CW) plasma. The consequence is that for a given synchronous RF biasing of a wafer-chuck, the ion energy is much higher in the pulsed plasma than it is in the CW plasma of chlorine/chlorosilane. Under these conditions, the wafer is bombarded by a low flux of very energetic ions, very much as it would in a low density, capacitively coupled plasma. Therefore, one can extend the operating range of ICPs through synchronous pulsing of the inductive excitation and capacitive chuck-bias, offering new means by which to control plasma etching.

  20. Accuracy of quantum sensors measuring yield photon flux and photosynthetic photon flux

    NASA Technical Reports Server (NTRS)

    Barnes, C.; Tibbitts, T.; Sager, J.; Deitzer, G.; Bubenheim, D.; Koerner, G.; Bugbee, B.; Knott, W. M. (Principal Investigator)

    1993-01-01

    Photosynthesis is fundamentally driven by photon flux rather than energy flux, but not all absorbed photons yield equal amounts of photosynthesis. Thus, two measures of photosynthetically active radiation have emerged: photosynthetic photon flux (PPF), which values all photons from 400 to 700 nm equally, and yield photon flux (YPF), which weights photons in the range from 360 to 760 nm according to plant photosynthetic response. We selected seven common radiation sources and measured YPF and PPF from each source with a spectroradiometer. We then compared these measurements with measurements from three quantum sensors designed to measure YPF, and from six quantum sensors designed to measure PPF. There were few differences among sensors within a group (usually <5%), but YPF values from sensors were consistently lower (3% to 20%) than YPF values calculated from spectroradiometric measurements. Quantum sensor measurements of PPF also were consistently lower than PPF values calculated from spectroradiometric measurements, but the differences were <7% for all sources, except red-light-emitting diodes. The sensors were most accurate for broad-band sources and least accurate for narrow-band sources. According to spectroradiometric measurements, YPF sensors were significantly less accurate (>9% difference) than PPF sensors under metal halide, high-pressure sodium, and low-pressure sodium lamps. Both sensor types were inaccurate (>18% error) under red-light-emitting diodes. Because both YPF and PPF sensors are imperfect integrators, and because spectroradiometers can measure photosynthetically active radiation much more accurately, researchers should consider developing calibration factors from spectroradiometric data for some specific radiation sources to improve the accuracy of integrating sensors.

  1. Quantum Paramagnet in a π Flux Triangular Lattice Hubbard Model.

    PubMed

    Rachel, Stephan; Laubach, Manuel; Reuther, Johannes; Thomale, Ronny

    2015-04-24

    We propose the π flux triangular lattice Hubbard model (π THM) as a prototypical setup to stabilize magnetically disordered quantum states of matter in the presence of charge fluctuations. The quantum paramagnetic domain of the π THM that we identify for intermediate Hubbard U is framed by a Dirac semimetal for weak coupling and by 120° Néel order for strong coupling. Generalizing the Klein duality from spin Hamiltonians to tight-binding models, the π THM maps to a Hubbard model which corresponds to the (J_{H},J_{K})=(-1,2) Heisenberg-Kitaev model in its strong coupling limit. The π THM provides a promising microscopic testing ground for exotic finite-U spin liquid ground states amenable to numerical investigation. PMID:25955072

  2. Ablation characteristics of quantum square pulse mode dental erbium laser

    NASA Astrophysics Data System (ADS)

    Lukač, Nejc; Suhovršnik, Tomaž; Lukač, Matjaž; Jezeršek, Matija

    2016-01-01

    Erbium lasers are by now an accepted tool for performing ablative medical procedures, especially when minimal invasiveness is desired. Ideally, a minimally invasive laser cutting procedure should be fast and precise, and with minimal pain and thermal side effects. All these characteristics are significantly influenced by laser pulse duration, albeit not in the same manner. For example, high cutting efficacy and low heat deposition are characteristics of short pulses, while vibrations and ejected debris screening are less pronounced at longer pulse durations. We report on a study of ablation characteristics on dental enamel and cementum, of a chopped-pulse Er:YAG [quantum square pulse (QSP)] mode, which was designed to reduce debris screening during an ablation process. It is shown that in comparison to other studied standard Er:YAG and Er,Cr:YSGG laser pulse duration modes, the QSP mode exhibits the highest ablation drilling efficacy with lowest heat deposition and reduced vibrations, demonstrating that debris screening has a considerable influence on the ablation process. By measuring single-pulse ablation depths, we also show that tissue desiccation during the consecutive delivery of laser pulses leads to a significant reduction of the intrinsic ablation efficacy that cannot be fully restored under clinical settings by rehydrating the tooth using an external water spray.

  3. Phase-controlled superconducting heat-flux quantum modulator

    NASA Astrophysics Data System (ADS)

    Giazotto, F.; Martínez-Pérez, M. J.

    2012-09-01

    We theoretically put forward the concept of a phase-controlled superconducting heat-flux quantum modulator. Its operation relies on phase-dependent heat current predicted to occur in temperature-biased Josephson tunnel junctions. The device behavior is investigated as a function of temperature bias across the junctions, bath temperature, and junctions asymmetry as well. In a realistic Al-based setup the structure could provide temperature modulation amplitudes up to ˜50 mK with flux-to-temperature transfer coefficients exceeding ˜125 mK/Φ0 below 1 K, and temperature modulation frequency of the order of a few MHz. The proposed structure appears as a promising building-block for the implementation of caloritronic devices operating at cryogenic temperatures.

  4. 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.

  5. Luminescent graphene quantum dots fabricated by pulsed laser synthesis

    PubMed Central

    Habiba, Khaled; Makarov, Vladimir I.; Avalos, Javier; Guinel, Maxime J.F.; Weiner, Brad R.; Morell, Gerardo

    2016-01-01

    Graphene has been the subject of intense research in recent years due to its unique electrical, optical and mechanical properties. Furthermore, it is expected that quantum dots of graphene would make their way into devices due to their structure and composition which unify graphene and quantum dots properties. Graphene quantum dots (GQDs) are planar nano flakes with a few atomic layers thick and with a higher surface-to-volume ratio than spherical carbon dots (CDs) of the same size. We have developed a pulsed laser synthesis (PLS) method for the synthesis of GQDs that are soluble in water, measure 2–6 nm across, and are about 1–3 layers thick. They show strong intrinsic fluorescence in the visible region. The source of fluorescence can be attributed to various factors, such as: quantum confinement, zigzag edge structure, and surface defects. Confocal microscopy images of bacteria exposed to GQDs show their suitability as biomarkers and nano-probes in high contrast bioimaging.

  6. Monitoring of Ethylene by a Pulsed Quantum Cascade Laser

    NASA Astrophysics Data System (ADS)

    Weidmann, Damien; Kosterev, Anatoliy A.; Roller, Chad; Curl, Robert F.; Fraser, Matthew P.; Tittel, Frank K.

    2004-06-01

    We report on the development and performance of a gas sensor based on a quantum cascade laser operating at a wavelength of ~10 µm to measure ethylene (C2H4) concentrations by use of a rotational component of the fundamental nu_7 band. The laser is thermoelectrically cooled and operates in a pulsed mode. The influence of pulse-to-pulse fluctuations is minimized by use of a reference beam and a single detector with time discriminating electronics. Gas absorption is recorded in a 100-m optical path-length astigmatic Herriott cell. With a 10-kHz pulse repetition rate and an 80-s total acquisition time, a noise equivalent sensitivity of 30 parts per billion has been demonstrated. The sensor has been applied to monitor C2H4 in vehicle exhaust as well as in air collected in a high-traffic urban tunnel.

  7. Magnetically coupled quantum-flux-latch with wide operation margins

    NASA Astrophysics Data System (ADS)

    Tsuji, Naoki; Takeuchi, Naoki; Narama, Tatsuya; Ortlepp, Thomas; Yamanashi, Yuki; Yoshikawa, Nobuyuki

    2015-11-01

    We have been developing adiabatic quantum-flux-parametron (AQFP) circuits as an ultra-low-power superconductor logic for energy-efficient computing. In a previous study, we proposed and demonstrated a quantum-flux-latch (QFL), which is a compact and compatible latch for AQFP logic. The QFL is composed of an AQFP buffer gate and a storage loop, which are directly connected to each other. However, the operation margins were not sufficiently wide due to a trade-off between the operation margins of the storage loop and that of the buffer gate. In this present study, we propose a magnetically coupled QFL (MC-QFL), where the storage loop and the buffer gate are physically separated and magnetically coupled to each other to eliminate the trade-off in the operation margins. The simulation results showed that the critical parameter margin of the MC-QFL is twice as large as that of the previously designed QFL. For comparison, we fabricated and demonstrated both the previously designed QFL and the newly designed MC-QFL. The measurement results showed that the MC-QFL has wider operation margins compared with the previously designed QFL.

  8. Heat flux and quantum correlations in dissipative cascaded systems

    NASA Astrophysics Data System (ADS)

    Lorenzo, Salvatore; Farace, Alessandro; Ciccarello, Francesco; Palma, G. Massimo; Giovannetti, Vittorio

    2015-02-01

    We study the dynamics of heat flux in the thermalization process of a pair of identical quantum systems that interact dissipatively with a reservoir in a cascaded fashion. Despite that the open dynamics of the bipartite system S is globally Lindbladian, one of the subsystems "sees" the reservoir in a state modified by the interaction with the other subsystem and hence it undergoes a non-Markovian dynamics. As a consequence, the heat flow exhibits a nonexponential time behavior which can greatly deviate from the case where each party is independently coupled to the reservoir. We investigate both thermal and correlated initial states of S and show that the presence of correlations at the beginning can considerably affect the heat-flux rate. We carry out our study in two paradigmatic cases—a pair of harmonic oscillators with a reservoir of bosonic modes and two qubits with a reservoir of fermionic modes—and compare the corresponding behaviors. In the case of qubits and for initial thermal states, we find that the trace distance discord is at any time interpretable as the correlated contribution to the total heat flux.

  9. Analysis of femtosecond quantum control mechanisms with colored double pulses

    SciTech Connect

    Vogt, Gerhard; Nuernberger, Patrick; Selle, Reimer; Dimler, Frank; Brixner, Tobias; Gerber, Gustav

    2006-09-15

    Fitness landscapes based on a limited number of laser pulse shape parameters can elucidate reaction pathways and can help to find the underlying control mechanism of optimal pulses determined by adaptive femtosecond quantum control. In a first experiment, we employ colored double pulses and systematically scan both the temporal subpulse separation and the relative amplitude of the two subpulses to acquire fitness landscapes. Comparison with results obtained from a closed-loop experiment demonstrates the capability of fitness landscapes for the revelation of possible control mechanisms. In a second experiment, using transient absorption spectroscopy, we investigate and compare the dependence of the excitation efficiency of the solvated dye molecule 5,5{sup '}-dichloro-11-diphenylamino-3,3{sup '}-diethyl-10,12-ethylene thiatricarbocyanine perchlorate (IR140) on selected pulse shapes in two parametrizations. The results show that very different pulse profiles can be equivalently adequate to maximize a given control objective. Fitness landscapes thus provide valuable information about different pathways along which a molecular system can be controlled with shaped laser pulses.

  10. Complete quantum control of a single quantum dot spin using ultrafast optical pulses.

    PubMed

    Press, David; Ladd, Thaddeus D; Zhang, Bingyang; Yamamoto, Yoshihisa

    2008-11-13

    A basic requirement for quantum information processing systems is the ability to completely control the state of a single qubit. For qubits based on electron spin, a universal single-qubit gate is realized by a rotation of the spin by any angle about an arbitrary axis. Driven, coherent Rabi oscillations between two spin states can be used to demonstrate control of the rotation angle. Ramsey interference, produced by two coherent spin rotations separated by a variable time delay, demonstrates control over the axis of rotation. Full quantum control of an electron spin in a quantum dot has previously been demonstrated using resonant radio-frequency pulses that require many spin precession periods. However, optical manipulation of the spin allows quantum control on a picosecond or femtosecond timescale, permitting an arbitrary rotation to be completed within one spin precession period. Recent work in optical single-spin control has demonstrated the initialization of a spin state in a quantum dot, as well as the ultrafast manipulation of coherence in a largely unpolarized single-spin state. Here we demonstrate complete coherent control over an initialized electron spin state in a quantum dot using picosecond optical pulses. First we vary the intensity of a single optical pulse to observe over six Rabi oscillations between the two spin states; then we apply two sequential pulses to observe high-contrast Ramsey interference. Such a two-pulse sequence realizes an arbitrary single-qubit gate completed on a picosecond timescale. Along with the spin initialization and final projective measurement of the spin state, these results demonstrate a complete set of all-optical single-qubit operations. PMID:19005550

  11. Combined Flux Compression and Plasma Opening Switch on the Saturn Pulsed Power Generator

    SciTech Connect

    Felber, Franklin S.; Waisman, Eduardo M.; Mazarakis, Michael G.

    2010-05-07

    A wire-array flux-compression cartridge installed on Sandia's Saturn pulsed power generator doubled the current into a 3-nH load to 6 MA and halved its rise time to 100 ns. The current into the load, however, was unexpectedly delayed by almost 1 {mu}s. Estimates of a plasma flow switch acting as a long-conduction-time opening switch are consistent with key features of the power compression. The results suggest that microsecond-conduction-time plasma flow switches can be combined with flux compression both to amplify currents and to sharpen pulse rise times in pulsed power drivers.

  12. Study of mass and cluster flux in a pulsed gas system with enhanced nanoparticle aggregation

    NASA Astrophysics Data System (ADS)

    Drache, Steffen; Stranak, Vitezslav; Hubicka, Zdenek; Berg, Florian; Tichy, Milan; Helm, Christiane A.; Hippler, Rainer

    2014-10-01

    The paper is focused on investigation of enhanced metal (Cu) cluster growth in a source of Haberland's type using pulsed gas aggregation. The aggregation Ar gas was delivered into the cluster source in a pulse regime, which results in the formation of well pronounced aggregation pressure peaks. The pressure peaks were varied by varying the different pulse gas frequency at the same mean pressure kept for all experiments. Hence, we were able to study the effect of enhanced aggregation pressure on cluster formation. Time-resolved measurements of cluster mass distribution were performed to estimate the mass and particle flux. The paper demonstrates that pulse gas aggregation influences growth of Cu nanoparticles, i.e., cluster mass/size, mass flux, and particle flux emitted from the cluster source. It was found that cluster mass related quantities are strongly influenced by pulsed gas frequency; the highest value of mass flux appears at the most pronounced pressure peaks. On the other hand, the particle flux depends only slightly on the gas pulse frequency. The explanation based on cooling and thermalization of sputtered particles is discussed in the paper.

  13. Reprint of : Flux sensitivity of quantum spin Hall rings

    NASA Astrophysics Data System (ADS)

    Crépin, F.; Trauzettel, B.

    2016-08-01

    We analyze the periodicity of persistent currents in quantum spin Hall loops, partly covered with an s-wave superconductor, in the presence of a flux tube. Much like in normal (non-helical) metals, the periodicity of the single-particle spectrum goes from Φ0 = h / e to Φ0 / 2 as the length of the superconductor is increased past the coherence length of the superconductor. We further analyze the periodicity of the persistent current, which is a many-body effect. Interestingly, time reversal symmetry and parity conservation can significantly change the period. We find a 2Φ0-periodic persistent current in two distinct regimes, where one corresponds to a Josephson junction and the other one to an Aharonov-Bohm setup.

  14. Adiabatic quantum-flux-parametron cell library adopting minimalist design

    NASA Astrophysics Data System (ADS)

    Takeuchi, Naoki; Yamanashi, Yuki; Yoshikawa, Nobuyuki

    2015-05-01

    We herein build an adiabatic quantum-flux-parametron (AQFP) cell library adopting minimalist design and a symmetric layout. In the proposed minimalist design, every logic cell is designed by arraying four types of building block cells: buffer, NOT, constant, and branch cells. Therefore, minimalist design enables us to effectively build and customize an AQFP cell library. The symmetric layout reduces unwanted parasitic magnetic coupling and ensures a large mutual inductance in an output transformer, which enables very long wiring between logic cells. We design and fabricate several logic circuits using the minimal AQFP cell library so as to test logic cells in the library. Moreover, we experimentally investigate the maximum wiring length between logic cells. Finally, we present an experimental demonstration of an 8-bit carry look-ahead adder designed using the minimal AQFP cell library and demonstrate that the proposed cell library is sufficiently robust to realize large-scale digital circuits.

  15. Adiabatic quantum-flux-parametron cell library adopting minimalist design

    SciTech Connect

    Takeuchi, Naoki; Yamanashi, Yuki; Yoshikawa, Nobuyuki

    2015-05-07

    We herein build an adiabatic quantum-flux-parametron (AQFP) cell library adopting minimalist design and a symmetric layout. In the proposed minimalist design, every logic cell is designed by arraying four types of building block cells: buffer, NOT, constant, and branch cells. Therefore, minimalist design enables us to effectively build and customize an AQFP cell library. The symmetric layout reduces unwanted parasitic magnetic coupling and ensures a large mutual inductance in an output transformer, which enables very long wiring between logic cells. We design and fabricate several logic circuits using the minimal AQFP cell library so as to test logic cells in the library. Moreover, we experimentally investigate the maximum wiring length between logic cells. Finally, we present an experimental demonstration of an 8-bit carry look-ahead adder designed using the minimal AQFP cell library and demonstrate that the proposed cell library is sufficiently robust to realize large-scale digital circuits.

  16. Mixed quantum-classical equilibrium in global flux surface hopping

    SciTech Connect

    Sifain, Andrew E.; Wang, Linjun; Prezhdo, Oleg V.

    2015-06-14

    Global flux surface hopping (GFSH) generalizes fewest switches surface hopping (FSSH)—one of the most popular approaches to nonadiabatic molecular dynamics—for processes exhibiting superexchange. We show that GFSH satisfies detailed balance and leads to thermodynamic equilibrium with accuracy similar to FSSH. This feature is particularly important when studying electron-vibrational relaxation and phonon-assisted transport. By studying the dynamics in a three-level quantum system coupled to a classical atom in contact with a classical bath, we demonstrate that both FSSH and GFSH achieve the Boltzmann state populations. Thermal equilibrium is attained significantly faster with GFSH, since it accurately represents the superexchange process. GFSH converges closer to the Boltzmann averages than FSSH and exhibits significantly smaller statistical errors.

  17. Optimal quantum control via numerical pulse shape optimization for two exciton qubits confined to semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Mathew, Reuble; Shi Yang, Hong Yi; Hall, Kimberley

    2015-03-01

    Optimal quantum control (OQC), which iteratively optimizes the control Hamiltonian to achieve a target quantum state, is a versatile approach for manipulating quantum systems. For optically-active transitions, OQC can be implemented using femtosecond pulse shaping which provides control over the amplitude and/or phase of the electric field. Optical pulse shaping has been employed to optimize physical processes such as nonlinear optical signals, photosynthesis, and has recently been applied to optimizing single-qubit gates in multiple semiconductor quantum dots. In this work, we examine the use of numerical pulse shape optimization for optimal quantum control of multiple qubits confined to quantum dots as a function of their electronic structure parameters. The numerically optimized pulse shapes were found to produce high fidelity quantum gates for a range of transition frequencies, dipole moments, and arbitrary initial and final states. This work enhances the potential for scalability by reducing the laser resources required to control multiple qubits.

  18. Optical measurement on quantum cascade lasers using femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Cai, Hong

    Quantum cascade lasers (QCLs) as the state-of-the-art mid-infrared (mid-IR) coherent sources have been greatly developed in aspects such as output power, energy efficiency and spectral purity. However, there are additional applications of QCLs in high demand, namely mode-locking, mid-IR modulation, etc. The inherent optical properties and ultrafast carrier dynamics can lead to solutions to these challenges. In this dissertation, we further characterize QCLs using mid-IR femtosecond (fs) pulses generated from a laser system consisting of a Ti:sapphire oscillator, a Ti:sapphire regenerative amplifier, an optical parametric amplifier and a difference frequency generator. We study the Kerr nonlinearity of QCLs by coupling resonant and off-resonant mid-IR fs pulses into an active QCL waveguide. We observe an increase in the spectral width of the transmitted fs pulses as the coupled mid-IR pulse power increases. This is explained by the self-phase modulation effect due to the large Kerr nonlinearity of QCL waveguides. We further confirm this effect by observing the intensity dependent far-field profile of the transmitted mid-IR pulses, showing the pulses undergo self-focusing as they propagate through the active QCL due to the intensity dependent refractive index. The finite-difference time-domain simulations of QCL waveguides with Kerr nonlinearity incorporated show similar behavior to the experimental results. The giant Kerr nonlinearity investigated here may be used to realize ultrafast pulse generation in QCLs. In addition, we temporally resolved the ultrafast mid-infrared transmission modulation of QCLs using a near-infrared pump/mid-infrared probe technique at room temperature. Two different femtosecond wavelength pumps are used with photon energy above and below the quantum well (QW) bandgap. The shorter wavelength pump modulates the mid-infrared probe transmission through interband transition assisted mechanisms, resulting in a high transmission modulation depth

  19. Nonresonant interaction of ultrashort electromagnetic pulses with multilevel quantum systems

    NASA Technical Reports Server (NTRS)

    Belenov, E.; Isakov, V.; Nazarkin, A.

    1994-01-01

    Some features of the excitation of multilevel quantum systems under the action of electromagnetic pulses which are shorter than the inverse frequency of interlevel transitions are considered. It is shown that the interaction is characterized by a specific type of selectivity which is not connected with the resonant absorption of radiation. The simplest three-level model displays the inverse population of upper levels. The effect of an ultrashort laser pulse on a multilevel molecule was regarded as an instant reception of the oscillation velocity by the oscillator and this approach showed an effective excitation and dissociation of the molecule. The estimations testify to the fact that these effects can be observed using modern femtosecond lasers.

  20. Generation of quantum electrodynamic cascades by colliding laser pulses

    NASA Astrophysics Data System (ADS)

    Gelfer, E. G.

    2016-04-01

    Quantum electrodynamic cascades in intense electromagnetic fields arise when the proper electron acceleration χ, expressed in Compton units, can attain values greater than or on the order of unity. For times t ll 1/ω, where ω is the carrier frequency of the field, we have derived a general formula for χ of an initially resting electron in an arbitrary electromagnetic field. Using this formula, we have found an optimal configuration of colliding laser pulses, which provides a significant reduction in the threshold intensity of occurrence of cascades up to a level of ~1023 W cm-2.

  1. Observation of 65 GHz Coherent Oscillation in a Superconducting Flux Qubit Manipulated by Pulses

    NASA Astrophysics Data System (ADS)

    F, Chiarello; P, Carelli; G, Castellano M.; C, Cosmelli; G, Torrioli

    2014-05-01

    A superconducting flux qubit can be manipulated by a fast modification of its potential, with a rapid transition from a double well to a single well shape, and coming back to the initial condition. This mechanism is based on a non-trivial quantum phenomenon, involving "partial" Landau-Zener transitions, coherent evolution in an harmonic potential and quantum interference. The study of this system enables a deep insight in decoherence mechanisms typical of superconducting qubits. Moreover, this procedure allows quantum operations with extreme high speeds, not possible with other standard manipulations. We present the experimental observation of coherent oscillations showing tunable frequencies with a 65 GHz top value.

  2. Controlled Fluxes of Silicon Nanoparticles By Extraction from a Pulsed RF Plasma

    NASA Astrophysics Data System (ADS)

    Girshick, Steven; Larriba-Andaluz, Carlos

    2015-09-01

    Deposition of silicon nanoparticles onto substrates may be a means of growing monocrystalline silicon films at low substrate temperature if the nanoparticles' impact energy and size can be controlled to provide melting or amorphization of the nanoparticle without damaging the underlying film. In order to explore conditions that could produce such controlled fluxes of nanoparticles we numerically model a pulsed RF argon-silane plasma, with a positive DC bias applied during the afterglow phase of each pulse so as to extract and accelerate negatively charged silicon particles. Operating parameters studied include pulse on time, pulse off time, DC bias voltage, RF voltage and pressure. This set of parameters is tested to find conditions under which one can achieve a periodic steady state with repeatable pulse-to-pulse conditions that maximize silicon film growth rates while maintaining nanoparticle impact energies in the range 0.5-2.0 eV/atom. We utilize a previously developed 1-D dusty plasma numerical model, modified to consider pulsing and applied substrate bias. This model self-consistently solves for the coupled behavior of plasma, chemistry, and aerosol. Results show that it is possible by this method to produce nanoparticle fluxes that are tailored with respect to their distribution of impact energies and mass deposition rates. Partially supported by US Dept. of Energy Office of Fusion Energy Science (DE-SC0001939), US National Science Foundation (CHE-124752), and Minnesota Supercomputing Institute.

  3. Optically engineered ultrafast pulses for controlled rotations of exciton qubits in semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Gamouras, Angela; Mathew, Reuble; Hall, Kimberley C.

    2012-07-01

    Shaped ultrafast pulses designed for controlled-rotation (C-ROT) operations on exciton qubits in semiconductor quantum dots are demonstrated using a quantum control apparatus operating at ˜1 eV. Optimum pulse shapes employing amplitude and phase shaping protocols are implemented using the output of an optical parametric oscillator and a programmable pulse shaping system, and characterized using autocorrelation and multiphoton intrapulse interference phase scan techniques. We apply our pulse characterization results and density matrix simulations to assess the fundamental limits on the fidelity of the C-ROT operation, providing a benchmark for the evaluation of sources of noise in other quantum control experiments. Our results indicate the effectiveness of pulse shaping techniques for achieving high fidelity quantum operations in quantum dots with a gate time below 1 ps.

  4. Band-selective shaped pulse for high fidelity quantum control in diamond

    SciTech Connect

    Chang, Yan-Chun; Xing, Jian; Liu, Gang-Qin; Jiang, Qian-Qing; Li, Wu-Xia; Zhang, Fei-Hao; Gu, Chang-Zhi; Pan, Xin-Yu; Long, Gui-Lu

    2014-06-30

    High fidelity quantum control of qubits is crucially important for realistic quantum computing, and it becomes more challenging when there are inevitable interactions between qubits. We introduce a band-selective shaped pulse, refocusing BURP (REBURP) pulse, to cope with the problems. The electron spin of nitrogen-vacancy centers in diamond is flipped with high fidelity by the REBURP pulse. In contrast with traditional rectangular pulses, the shaped pulse has almost equal excitation effect in a sharply edged region (in frequency domain). So the three sublevels of host {sup 14}N nuclear spin can be flipped accurately simultaneously, while unwanted excitations of other sublevels (e.g., of a nearby {sup 13}C nuclear spin) is well suppressed. Our scheme can be used for various applications such as quantum metrology, quantum sensing, and quantum information process.

  5. Band-selective shaped pulse for high fidelity quantum control in diamond

    NASA Astrophysics Data System (ADS)

    Chang, Yan-Chun; Xing, Jian; Zhang, Fei-Hao; Liu, Gang-Qin; Jiang, Qian-Qing; Li, Wu-Xia; Gu, Chang-Zhi; Long, Gui-Lu; Pan, Xin-Yu

    2014-06-01

    High fidelity quantum control of qubits is crucially important for realistic quantum computing, and it becomes more challenging when there are inevitable interactions between qubits. We introduce a band-selective shaped pulse, refocusing BURP (REBURP) pulse, to cope with the problems. The electron spin of nitrogen-vacancy centers in diamond is flipped with high fidelity by the REBURP pulse. In contrast with traditional rectangular pulses, the shaped pulse has almost equal excitation effect in a sharply edged region (in frequency domain). So the three sublevels of host 14N nuclear spin can be flipped accurately simultaneously, while unwanted excitations of other sublevels (e.g., of a nearby 13C nuclear spin) is well suppressed. Our scheme can be used for various applications such as quantum metrology, quantum sensing, and quantum information process.

  6. Influence of stem temperature changes on heat pulse sap flux density measurements.

    PubMed

    Vandegehuchte, Maurits W; Burgess, Stephen S O; Downey, Alec; Steppe, Kathy

    2015-04-01

    While natural spatial temperature gradients between measurement needles have been thoroughly investigated for continuous heat-based sap flow methods, little attention has been given to how natural changes in stem temperature impact heat pulse-based methods through temporal rather than spatial effects. By modelling the theoretical equation for both an ideal instantaneous pulse and a step pulse and applying a finite element model which included actual needle dimensions and wound effects, the influence of a varying stem temperature on heat pulse-based methods was investigated. It was shown that the heat ratio (HR) method was influenced, while for the compensation heat pulse and Tmax methods changes in stem temperatures of up to 0.002 °C s(-1) did not lead to significantly different results. For the HR method, rising stem temperatures during measurements led to lower heat pulse velocity values, while decreasing stem temperatures led to both higher and lower heat pulse velocities, and to imaginary results for high flows. These errors of up to 40% can easily be prevented by including a temperature correction in the data analysis procedure, calculating the slope of the natural temperature change based on the measured temperatures before application of the heat pulse. Results of a greenhouse and outdoor experiment on Pinus pinea L. show the influence of this correction on low and average sap flux densities. PMID:25145698

  7. Quantum description and properties of electrons emitted from pulsed nanotip electron sources

    SciTech Connect

    Lougovski, Pavel; Batelaan, Herman

    2011-08-15

    We present a quantum calculation of the electron degeneracy for electron sources. We explore quantum interference of electrons in the temporal and spatial domain and demonstrate how it can be utilized to characterize a pulsed electron source. We estimate effects of Coulomb repulsion on two-electron interference and show that currently available pulsed nanotip electron sources operate in the regime where the quantum nature of electrons can be made dominant.

  8. Quantum Hooke's Law to Classify Pulse Laser Induced Ultrafast Melting

    PubMed Central

    Hu, Hao; Ding, Hepeng; Liu, Feng

    2015-01-01

    Ultrafast crystal-to-liquid phase transition induced by femtosecond pulse laser excitation is an interesting material's behavior manifesting the complexity of light-matter interaction. There exist two types of such phase transitions: one occurs at a time scale shorter than a picosecond via a nonthermal process mediated by electron-hole plasma formation; the other at a longer time scale via a thermal melting process mediated by electron-phonon interaction. However, it remains unclear what material would undergo which process and why? Here, by exploiting the property of quantum electronic stress (QES) governed by quantum Hooke's law, we classify the transitions by two distinct classes of materials: the faster nonthermal process can only occur in materials like ice having an anomalous phase diagram characterized with dTm/dP < 0, where Tm is the melting temperature and P is pressure, above a high threshold laser fluence; while the slower thermal process may occur in all materials. Especially, the nonthermal transition is shown to be induced by the QES, acting like a negative internal pressure, which drives the crystal into a “super pressing” state to spontaneously transform into a higher-density liquid phase. Our findings significantly advance fundamental understanding of ultrafast crystal-to-liquid phase transitions, enabling quantitative a priori predictions. PMID:25645258

  9. Quantum Hooke's Law to classify pulse laser induced ultrafast melting

    DOE PAGESBeta

    Hu, Hao; Ding, Hepeng; Liu, Feng

    2015-02-03

    Ultrafast crystal-to-liquid phase transition induced by femtosecond pulse laser excitation is an interesting material's behavior manifesting the complexity of light-matter interaction. There exist two types of such phase transitions: one occurs at a time scale shorter than a picosecond via a nonthermal process mediated by electron-hole plasma formation; the other at a longer time scale via a thermal melting process mediated by electron-phonon interaction. However, it remains unclear what material would undergo which process and why? Here, by exploiting the property of quantum electronic stress (QES) governed by quantum Hooke's law, we classify the transitions by two distinct classes ofmore » materials: the faster nonthermal process can only occur in materials like ice having an anomalous phase diagram characterized with dTm/dP < 0, where Tm is the melting temperature and P is pressure, above a high threshold laser fluence; while the slower thermal process may occur in all materials. Especially, the nonthermal transition is shown to be induced by the QES, acting like a negative internal pressure, which drives the crystal into a “super pressing” state to spontaneously transform into a higher-density liquid phase. Our findings significantly advance fundamental understanding of ultrafast crystal-to-liquid phase transitions, enabling quantitative a priori predictions.« less

  10. Quantum Hooke's Law to classify pulse laser induced ultrafast melting

    SciTech Connect

    Hu, Hao; Ding, Hepeng; Liu, Feng

    2015-02-03

    Ultrafast crystal-to-liquid phase transition induced by femtosecond pulse laser excitation is an interesting material's behavior manifesting the complexity of light-matter interaction. There exist two types of such phase transitions: one occurs at a time scale shorter than a picosecond via a nonthermal process mediated by electron-hole plasma formation; the other at a longer time scale via a thermal melting process mediated by electron-phonon interaction. However, it remains unclear what material would undergo which process and why? Here, by exploiting the property of quantum electronic stress (QES) governed by quantum Hooke's law, we classify the transitions by two distinct classes of materials: the faster nonthermal process can only occur in materials like ice having an anomalous phase diagram characterized with dTm/dP < 0, where Tm is the melting temperature and P is pressure, above a high threshold laser fluence; while the slower thermal process may occur in all materials. Especially, the nonthermal transition is shown to be induced by the QES, acting like a negative internal pressure, which drives the crystal into a “super pressing” state to spontaneously transform into a higher-density liquid phase. Our findings significantly advance fundamental understanding of ultrafast crystal-to-liquid phase transitions, enabling quantitative a priori predictions.

  11. Measurement of the Magnetic Flux Noise Spectrum in Superconducting Xmon Transmon Quantum Bits

    NASA Astrophysics Data System (ADS)

    Chiaro, Ben; Sank, D.; Kelly, J.; Chen, Z.; Campbell, B.; Dunsworth, A.; O'Malley, P.; Neill, C.; Quintana, C.; Vainsencher, A.; Wenner, J.; Barends, R.; Chen, Y.; Fowler, A.; Jeffrey, E.; Migrant, A.; Mutus, J.; Roushan, P.; White, T.; Martinis, J. M.

    Dephasing induced by magnetic flux noise limits the performance of modern superconducting quantum processors. We measure the flux noise power spectrum in planar, frequency-tunable, Xmon transmon quantum bits (qubits), with several SQUID loop geometries. We extend the Ramsey Tomography Oscilloscope (RTO) technique by rapid sampling up to 1 MHz, without state reset, to measure the flux noise power spectrum between 10-2 and 105 Hz. The RTO measurements are combined with idle gate randomized benchmarking and Ramsey decay to give a more complete picture of dephasing in SQUID-based devices.

  12. Soil carbon flux following pulse precipitation events in the shortgrass steppe

    USGS Publications Warehouse

    Munson, S.M.; Benton, T.J.; Lauenroth, W.K.; Burke, I.C.

    2010-01-01

    Pulses of water availability characterize semiarid and arid ecosystems. Most precipitation events in these ecosystems are small (???10 mm), but can stimulate carbon flux. The large proportion of carbon stored belowground and small carbon inputs create the potential for these small precipitation events to have large effects on carbon cycling. Land-use change can modify these effects through alteration of the biota and soil resources. The goal of our research was to determine how small precipitation events (2, 5, and 10 mm) affected the dynamics of soil carbon flux and water loss in previously cultivated Conservation Reserve Program (CRP) fields and undisturbed shortgrass steppe. Total carbon loss and duration of elevated carbon flux increased as event size increased in all field types. Time since cultivation increased in importance for carbon flux as event size increased. A comparison of water loss rates to carbon flux suggests that water is limiting to carbon flux for the smallest events, but is less limiting for events above 5 mm. We also describe how water availability interacts with temperature in controlling carbon flux rate. We conclude that small precipitation events have the potential for large short-term losses of carbon in the shortgrass steppe. ?? 2009 The Ecological Society of Japan.

  13. Quantum reaction rate from higher derivatives of the thermal flux-flux autocorrelation function at time zero.

    PubMed

    Ceotto, Michele; Yang, Sandy; Miller, William H

    2005-01-22

    A quantum theory of thermal reaction rates is presented which may be viewed as an extension of the recently developed "quantum instanton" (QI) model [W. H. Miller, Y. Zhao, M. Ceotto, and S. Yang, J. Chem. Phys. 119, 1329 (2003)]. It is based on using higher derivatives of the flux-flux autocorrelation function C(t) (as given by Miller, Schwartz, and Tromp) at t=0 to construct a short time approximation for C(t). Tests of this theory on 1d and collinear reactions, both symmetric and asymmetric, show it to be more accurate than the original QI model, giving rate constants to approximately 5% for a wide range of temperature. PMID:15740237

  14. Quantum reaction rate from higher derivatives of the thermal flux-flux autocorrelation function at time zero

    NASA Astrophysics Data System (ADS)

    Ceotto, Michele; Yang, Sandy; Miller, William H.

    2005-01-01

    A quantum theory of thermal reaction rates is presented which may be viewed as an extension of the recently developed "quantum instanton" (QI) model [W. H. Miller, Y. Zhao, M. Ceotto, and S. Yang, J. Chem. Phys. 119, 1329 (2003)]. It is based on using higher derivatives of the flux-flux autocorrelation function C(t) (as given by Miller, Schwartz, and Tromp) at t=0 to construct a short time approximation for C(t). Tests of this theory on 1d and collinear reactions, both symmetric and asymmetric, show it to be more accurate than the original QI model, giving rate constants to ˜5% for a wide range of temperature.

  15. Neutron Radiography Facility at IBR-2 High Flux Pulsed Reactor: First Results

    NASA Astrophysics Data System (ADS)

    Kozlenko, D. P.; Kichanov, S. E.; Lukin, E. V.; Rutkauskas, A. V.; Bokuchava, G. D.; Savenko, B. N.; Pakhnevich, A. V.; Rozanov, A. Yu.

    A neutron radiography and tomography facilityhave been developed recently at the IBR-2 high flux pulsed reactor. The facility is operated with the CCD-camera based detector having maximal field of view of 20x20 cm, and the L/D ratio can be varied in the range 200 - 2000. The first results of the radiography and tomography experiments with industrial materials and products, paleontological and geophysical objects, meteorites, are presented.

  16. Flux jumps in high-J c MgB2 bulks during pulsed field magnetization

    NASA Astrophysics Data System (ADS)

    Fujishiro, H.; Mochizuki, H.; Naito, T.; Ainslie, M. D.; Giunchi, G.

    2016-03-01

    Pulsed field magnetization (PFM) of a high-J c MgB2 bulk disk has been investigated at 20 K, in which flux jumps frequently occur for high pulsed fields. Using a numerical simulation of the PFM procedure, we estimated the time dependence of the local magnetic field and temperature during PFM. We analyzed the electromagnetic and thermal instability of the high-J c MgB2 bulk to avoid flux jumps using the time dependence of the critical thickness, d c(t), which shows the upper safety thickness to stabilize the superconductor magnetically, and the minimum propagation zone length, l m(t), to obtain dynamical stability. The values of d c(t) and l m(t) change along the thermally-stabilized direction with increasing temperature below the critical temperature, T c. However, the flux jump can be qualitatively understood by the local temperature, T(t), which exceeds T c in the bulk. Finally, possible solutions to avoid flux jumps in high-J c MgB2 bulks are discussed.

  17. Quantum coherence induces pulse shape modification in a semiconductor optical amplifier at room temperature

    PubMed Central

    Kolarczik, Mirco; Owschimikow, Nina; Korn, Julian; Lingnau, Benjamin; Kaptan, Yücel; Bimberg, Dieter; Schöll, Eckehard; Lüdge, Kathy; Woggon, Ulrike

    2013-01-01

    Coherence in light–matter interaction is a necessary ingredient if light is used to control the quantum state of a material system. Coherent effects are firmly associated with isolated systems kept at low temperature. The exceedingly fast dephasing in condensed matter environments, in particular at elevated temperatures, may well erase all coherent information in the material at timescales shorter than a laser excitation pulse. Here we show for an ensemble of semiconductor quantum dots that even in the presence of ultrafast dephasing, for suitably designed condensed matter systems quantum-coherent effects are robust enough to be observable at room temperature. Our conclusions are based on an analysis of the reshaping an ultrafast laser pulse undergoes on propagation through a semiconductor quantum dot amplifier. We show that this pulse modification contains the signature of coherent light–matter interaction and can be controlled by adjusting the population of the quantum dots via electrical injection. PMID:24336000

  18. Ultrasharp-front laser pulses generated by energetic-electron flux triggering of laser propagation in overdense plasmas

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Ya; Yu, Yong; Shen, Bai-Fei; Wang, Jia-Xiang; Zhu, Wen-Jun; Chen, Zi-Yu; Ye, Yan

    2013-08-01

    This paper reports that an initially opaque plasma foil, irradiated by a laser pulse with intensity below the self-induced transparency (SIT) threshold, will become transparent, if a flux of energetic electrons is present. Based on this phenomenon, named flux-induced transparency (FIT), an approach to obtaining ultrasharp-front laser pulses is proposed. With the presence of an energetic-electron flux generated by a p-polarized laser irradiating an overdense plasma foil from the rear side, the propagation of an s-polarized laser irradiating the front surface of the foil can be manipulated. The transmitted s-polarized laser pulse has an ultrasharp front which rises by three orders of magnitude within a few laser cycles. The profile of the transmitted pulse is tunable by controlling the time at which the energetic-electron flux arrives at the front surface.

  19. Three-dimensional Simulation of Magnetic Flux Dynamics and Temperature Rise in HTSC Bulk during Pulsed Field Magnetization

    NASA Astrophysics Data System (ADS)

    Fujishiro, H.; Naito, T.; Oyama, M.

    We have performed a three-dimensional (3D) numerical simulation of the dynamical motion of the magnetic flux and the heat propagation in the superconducting bulk after applying a pulsed magnetic field. An inhomogeneous Jc distribution was supposed in the bulk; the Jc in the growth sector boundary (GSB) is four times higher than that in the growth sector region (GSR). For lower applied pulsed field, magnetic flux was penetrated and trapped in the GSR, and for higher applied pulsed field, the magnetic flux was trapped more preferentially in the GSB. These results of the simulation reproduce the experimental ones and are valuable for the understanding the flux dynamics in the bulk during pulsed field magnetization.

  20. Behavior Genetics and the Within-Person Variability of Daily Interpersonal Styles: The Heritability of Flux, Spin and Pulse

    PubMed Central

    Markey, Patrick M.; Racine, Sarah E.; Markey, Charlotte N.; Hopwood, Christopher J.; Keel, Pamela K.; Burt, S. Alexandra; Neale, Michael C.; Sisk, Cheryl L.; Boker, Steven M.; Klump, Kelly L.

    2014-01-01

    A classical twin study was used to estimate the magnitude of genetic and environmental influences on four measurements of within-person variability: dominance flux, warmth flux, spin and pulse. Flux refers to the variability of an individual’s interpersonal dominance and warmth. Spin measures changes in the tone of interpersonal styles and pulse measures changes in the intensity of interpersonal styles. Daily reports of interpersonal styles were collected from 494 same-sex female twins (142 monozygotic pairs and 105 dizygotic pairs) over 45 days. For dominance flux, warmth flux, and spin, genetic effects accounted for a larger proportion of variance (37%, 24%, and 30%, respectively) than shared environmental effects (14%, 13%, 0%, respectively), with the remaining variance due to the non-shared environment (62%, 50%, 70% respectively). Pulse appeared to be primarily influenced by the non-shared environment, although conclusions about the contribution of familial influences were difficult to draw from this study. PMID:25977748

  1. Faint laser pulses versus a single-photon source in free space quantum cryptography

    NASA Astrophysics Data System (ADS)

    Molotkov, S. N.; Potapova, T. A.

    2016-03-01

    In this letter we present estimates for the distance of secret key transmission through free space for three different protocols of quantum key distribution: for BB84 and phase time-coding protocols in the case of a strictly single-photon source, and for the relativistic quantum key distribution protocol in the case of faint laser pulses.

  2. Quantum path control and isolated attosecond pulse generation with the combination of two circularly polarized laser pulses

    NASA Astrophysics Data System (ADS)

    Xia, Chang-Long; Liu, Xue-Shen

    2013-04-01

    We theoretically investigate the quantum paths of the high-order harmonic generation (HHG) by using a left and a right circularly polarized Gaussian laser pulse with a proper time delay. When the carrier phase of the two pulses is φ1=0, φ2=0.5π, the “gating” structure of the combined laser field disappears. The numerical results indicate that no “gating”-structure-combined laser pulse can control the quantum path. The HHG process is investigated by the semiclassical three-step model that makes use of a finite initial transverse velocity in the elliptically polarized field. For the case of λ1=800 nm, λ2=1600 nm, only a short quantum path contributes to the HHG, and an isolated attosecond pulse would be obtained. For the case of λ2=1600, φ2=0.5π, a supercontinuum spectrum plateau from 180 to 570 eV which includes the water window region is obtained, and attosecond pulses with the duration of about 75 as and a tunable central wavelength could be generated by superposing a bandwidth of 50 eV in the plateau area.

  3. Differential-phase-shift quantum key distribution with segmented pulse trains

    SciTech Connect

    Kawahara, Hiroki; Inoue, Kyo

    2011-06-15

    We present a modified scheme of differential-phase-shift (DPS) quantum key distribution (QKD) for improving its performance. A transmitter sends a weak coherent pulse train segmented with vacant pulses. Then, a receiver can find eavesdropping by monitoring the photon detection rate at particular time slots. Simulations show that the proposed scheme is robust against a sequential attack and a general individual attack.

  4. Ultrashort-Pulse Child-Langmuir Law in the Quantum and Relativistic Regimes

    SciTech Connect

    Ang, L. K.; Zhang, P.

    2007-04-20

    This Letter presents a consistent quantum and relativistic model of short-pulse Child-Langmuir (CL) law, of which the pulse length {tau} is less than the electron transit time in a gap of spacing D and voltage V. The classical value of the short-pulse CL law is enhanced by a large factor due to quantum effects when the pulse length and the size of the beam are, respectively, in femtosecond duration and nanometer scale. At high voltage larger than the electron rest mass, relativistic effects will suppress the enhancement of short-pulse CL law, which is confirmed by particle-in-cell simulation. When the pulse length is much shorter than the gap transit time, the current density is proportional to V, and to the inverse power of D and {tau}.

  5. Coherent control in quantum dot gain media using shaped pulses: a numerical study.

    PubMed

    Mishra, Akhilesh Kumar; Karni, Ouri; Eisenstein, Gadi

    2015-11-16

    We present a numerical study of coherent control in a room temperature InAs/InP quantum dot (QD) semiconductor optical amplifier (SOA) using shaped ultra-short pulses. Both the gain and absorption regimes were analyzed for pulses with central wavelengths lying on either side of the inhomogeneously broadened gain spectrum. The numerical experiments predict that in the gain regime the coherent interactions between a QD SOA and a pulse can be controlled by incorporating a quadratic spectral phase (QSP) in the pulse profile. The sequential interaction with the gain medium of different spectral components of the pulse results in either suppression or enhancement of the coherent signatures on the pulse profile depending upon their proximity to the gain spectrum peak. In the absorption regime, positive QSP induces a negative chirp that adds up to that of a two photon absorption induced Kerr-like effect resulting in pulse compression while negative QSP enhances dispersive broadening of the pulse. PMID:26698476

  6. Flux periodicities and quantum hair on holographic superconductors.

    PubMed

    Montull, Marc; Pujolàs, Oriol; Salvio, Alberto; Silva, Pedro J

    2011-10-28

    Superconductors in a cylindrical geometry respond periodically to a cylinder-threading magnetic flux, with the period changing from hc/2e to hc/e depending on whether the Aharonov-Bohm effects are suppressed. We show that holographic superconductors present a similar phenomenon, and that the different periodicities follow from classical no-hair theorems. We also give the Ginzburg-Landau description of the period-doubling phenomenon. PMID:22107621

  7. Fast neutron flux analyzer with real-time digital pulse shape discrimination

    NASA Astrophysics Data System (ADS)

    Ivanova, A. A.; Zubarev, P. V.; Ivanenko, S. V.; Khilchenko, A. D.; Kotelnikov, A. I.; Polosatkin, S. V.; Puryga, E. A.; Shvyrev, V. G.; Sulyaev, Yu. S.

    2016-08-01

    Investigation of subthermonuclear plasma confinement and heating in magnetic fusion devices such as GOL-3 and GDT at the Budker Institute (Novosibirsk, Russia) requires sophisticated equipment for neutron-, gamma- diagnostics and upgrading data acquisition systems with online data processing. Measurement of fast neutron flux with stilbene scintillation detectors raised the problem of discrimination of the neutrons (n) from background cosmic particles (muons) and neutron-induced gamma rays (γ). This paper describes a fast neutron flux analyzer with real-time digital pulse-shape discrimination (DPSD) algorithm FPGA-implemented for the GOL-3 and GDT devices. This analyzer was tested and calibrated with the help of 137Cs and 252Cf radiation sources. The Figures of Merit (FOM) calculated for different energy cuts are presented.

  8. Simultaneous SU(2) rotations on multiple quantum dot exciton qubits using a single shaped pulse

    NASA Astrophysics Data System (ADS)

    Mathew, Reuble; Yang, Hong Yi Shi; Hall, Kimberley C.

    2015-10-01

    Recent experimental demonstration of a parallel (π ,2 π ) single qubit rotation on excitons in two distant quantum dots [Nano Lett. 13, 4666 (2013), 10.1021/nl4018176] is extended in numerical simulations to the design of pulses for more general quantum state control, demonstrating the feasibility of full SU(2) rotations of each exciton qubit. Our results show that simultaneous high-fidelity quantum control is achievable within the experimentally accessible parameter space for commercial Fourier-domain pulse shaping systems. The identification of a threshold of distinguishability for the two quantum dots (QDs) for achieving high-fidelity parallel rotations, corresponding to a difference in transition energies of ˜0.25 meV , points to the possibility of controlling more than 10 QDs with a single shaped optical pulse.

  9. Why the two-pulse photon echo is not a good quantum memory protocol

    NASA Astrophysics Data System (ADS)

    Ruggiero, Jérôme; Le Gouët, Jean-Louis; Simon, Christoph; Chanelière, Thierry

    2009-05-01

    We consider in this paper a two-pulse photon echo sequence in the prospect of quantum light storage. We analyze the conditions where quantum storage could be realistically performed. We simply and analytically calculate the efficiency in that limit, and clarify the role of the exactly π -rephasing pulse in the sequence. Our physical interpretation of the process is well supported by its experimental implementation in a Tm3+ :yttrium aluminum garnet crystal thanks to an accurate control of the rephasing pulse area. We finally address independently the fundamental limitations of the quantum fidelity. Our work allows us to point out on one side the real drawbacks of this scheme for quantum storage and on the other side its specificities which can be a source of inspiration to conceive more promising procedures with rare-earth ion doped crystals.

  10. Why the two-pulse photon echo is not a good quantum memory protocol

    SciTech Connect

    Ruggiero, Jerome; Le Goueet, Jean-Louis; Chaneliere, Thierry; Simon, Christoph

    2009-05-15

    We consider in this paper a two-pulse photon echo sequence in the prospect of quantum light storage. We analyze the conditions where quantum storage could be realistically performed. We simply and analytically calculate the efficiency in that limit, and clarify the role of the exactly {pi}-rephasing pulse in the sequence. Our physical interpretation of the process is well supported by its experimental implementation in a Tm{sup 3+}:yttrium aluminum garnet crystal thanks to an accurate control of the rephasing pulse area. We finally address independently the fundamental limitations of the quantum fidelity. Our work allows us to point out on one side the real drawbacks of this scheme for quantum storage and on the other side its specificities which can be a source of inspiration to conceive more promising procedures with rare-earth ion doped crystals.

  11. Classical-quantum correspondence in atomic ionization by midinfrared pulses: Multiple peak and interference structures

    NASA Astrophysics Data System (ADS)

    Lemell, Christoph; Burgdörfer, Joachim; Gräfe, Stefanie; Dimitriou, Konstantinos I.; Arbó, Diego G.; Tong, Xiao-Min

    2013-01-01

    Atomic ionization by strong and ultrashort laser pulses with frequencies in the midinfrared spectral region have revealed novel features such as the low-energy structures. We have performed fully three-dimensional quantum dynamical as well as classical trajectory Monte Carlo simulations for pulses with wavelengths from λ=2000 to 6000 nm. Furthermore, we apply distorted-wave quantum approximations. This allows to explore the quantum-classical correspondence as well as the (non) perturbative character of the ionization dynamics driven by long-wavelength pulses. We observe surprisingly rich structures in the differential energy and angular momentum distribution which sensitively depend on λ, the pulse duration τp, and the carrier-envelope phase ϕCEP.

  12. Ultra-fast quantum randomness generation by accelerated phase diffusion in a pulsed laser diode.

    PubMed

    Abellán, C; Amaya, W; Jofre, M; Curty, M; Acín, A; Capmany, J; Pruneri, V; Mitchell, M W

    2014-01-27

    We demonstrate a high bit-rate quantum random number generator by interferometric detection of phase diffusion in a gain-switched DFB laser diode. Gain switching at few-GHz frequencies produces a train of bright pulses with nearly equal amplitudes and random phases. An unbalanced Mach-Zehnder interferometer is used to interfere subsequent pulses and thereby generate strong random-amplitude pulses, which are detected and digitized to produce a high-rate random bit string. Using established models of semiconductor laser field dynamics, we predict a regime of high visibility interference and nearly complete vacuum-fluctuation-induced phase diffusion between pulses. These are confirmed by measurement of pulse power statistics at the output of the interferometer. Using a 5.825 GHz excitation rate and 14-bit digitization, we observe 43 Gbps quantum randomness generation. PMID:24515170

  13. Storage of multiple single-photon pulses emitted from a quantum dot in a solid-state quantum memory

    PubMed Central

    Tang, Jian-Shun; Zhou, Zong-Quan; Wang, Yi-Tao; Li, Yu-Long; Liu, Xiao; Hua, Yi-Lin; Zou, Yang; Wang, Shuang; He, De-Yong; Chen, Geng; Sun, Yong-Nan; Yu, Ying; Li, Mi-Feng; Zha, Guo-Wei; Ni, Hai-Qiao; Niu, Zhi-Chuan; Li, Chuan-Feng; Guo, Guang-Can

    2015-01-01

    Quantum repeaters are critical components for distributing entanglement over long distances in presence of unavoidable optical losses during transmission. Stimulated by the Duan–Lukin–Cirac–Zoller protocol, many improved quantum repeater protocols based on quantum memories have been proposed, which commonly focus on the entanglement-distribution rate. Among these protocols, the elimination of multiple photons (or multiple photon-pairs) and the use of multimode quantum memory are demonstrated to have the ability to greatly improve the entanglement-distribution rate. Here, we demonstrate the storage of deterministic single photons emitted from a quantum dot in a polarization-maintaining solid-state quantum memory; in addition, multi-temporal-mode memory with 1, 20 and 100 narrow single-photon pulses is also demonstrated. Multi-photons are eliminated, and only one photon at most is contained in each pulse. Moreover, the solid-state properties of both sub-systems make this configuration more stable and easier to be scalable. Our work will be helpful in the construction of efficient quantum repeaters based on all-solid-state devices. PMID:26468996

  14. [Intra-pulse spectroscopy based on room-temperature pulsed quantum-cascade laser for N2O detection].

    PubMed

    Wang, Min; Zhang, Yu-Jun; Liu, Wen-Qing; Kan, Rui-Feng; Chen, Zhen-Yi; Tang, Yuan-Yuan; Liu, Jian-Guo

    2009-12-01

    Mid-infrared lasers are very suitable for high-sensitive trace-gases detection in that their wavelengths cover the fundamental absorption lines of most gases. Quantum-cascade lasers have been demonstrated to be ideal light sources with their especially high power, wide range of tuning capability and favorable operating condition on room-temperature. The intra-pulse spectroscopy based on a room-temperature distributed-feedback pulsed QC laser is a simple and effective trace gas detective method to detect trace-gas qualitatively or quantificationally. When a long excitation pulse is applied to a QC laser, the laser frequency tunes almost linearly to lower wave number (lower frequency) as a function of time so all absorption spectral elements are recorded during a single laser pulse. In the present paper, the method was introduced, and identification of N2O spectral fingerprint using this spectroscopy was demonstrated experimentally. The thermal chirp from a 500 ns long excitation pulse was applied to a quantum-cascade laser to get a fast wavelength scanning, thus a wave number tuning of about 1 cm(-1) was produced. The N2O absorption spectrum centered at 1 273.7 cm(-1) was also obtained. The measured absorption spectrum is consistent with HITRAN data precisely. PMID:20210127

  15. Pulse control of sudden transition for two qubits in XY spin baths and quantum phase transition

    SciTech Connect

    Luo, Da-Wei; Xu, Jing-Bo; Lin, Hai-Qing; Yao, Dao-Xin

    2011-12-15

    We study the dynamics of two initially correlated qubits coupled to their own separate spin baths modeled by an XY spin chain and find the explicit expression of the quantum discord for the system. A sudden transition is found to exist between classical and quantum decoherence by choosing certain initial states. We show that the sudden transition happens near the critical point, which provides an alternative way to characterize the quantum phase transition. Furthermore, we propose a scheme to prolong the transition time of the quantum discord by applying the bang-bang pulses.

  16. Pulsed nuclear pumping and spin diffusion in a single charged quantum dot.

    PubMed

    Ladd, Thaddeus D; Press, David; De Greve, Kristiaan; McMahon, Peter L; Friess, Benedikt; Schneider, Christian; Kamp, Martin; Höfling, Sven; Forchel, Alfred; Yamamoto, Yoshihisa

    2010-09-01

    We report the observation of a feedback process between the nuclear spins in a single charged quantum dot under coherently pulsed optical excitation and its trion transition. The optical pulse sequence intersperses resonant narrow-band pumping for spin initialization with off-resonant ultrafast pulses for coherent electron-spin rotation. A hysteretic sawtooth pattern in the free-induction decay of the single electron spin is observed; a mathematical model indicates a competition between optical nuclear pumping and nuclear spin-diffusion. This effect allows dynamic tuning of the electron Larmor frequency to a value determined by the pulse timing, potentially allowing more complex coherent control operations. PMID:20867546

  17. Time-optimal excitation of maximum quantum coherence: Physical limits and pulse sequences.

    PubMed

    Köcher, S S; Heydenreich, T; Zhang, Y; Reddy, G N M; Caldarelli, S; Yuan, H; Glaser, S J

    2016-04-28

    Here we study the optimum efficiency of the excitation of maximum quantum (MaxQ) coherence using analytical and numerical methods based on optimal control theory. The theoretical limit of the achievable MaxQ amplitude and the minimum time to achieve this limit are explored for a set of model systems consisting of up to five coupled spins. In addition to arbitrary pulse shapes, two simple pulse sequence families of practical interest are considered in the optimizations. Compared to conventional approaches, substantial gains were found both in terms of the achieved MaxQ amplitude and in pulse sequence durations. For a model system, theoretically predicted gains of a factor of three compared to the conventional pulse sequence were experimentally demonstrated. Motivated by the numerical results, also two novel analytical transfer schemes were found: Compared to conventional approaches based on non-selective pulses and delays, double-quantum coherence in two-spin systems can be created twice as fast using isotropic mixing and hard spin-selective pulses. Also it is proved that in a chain of three weakly coupled spins with the same coupling constants, triple-quantum coherence can be created in a time-optimal fashion using so-called geodesic pulses. PMID:27131527

  18. Time-optimal excitation of maximum quantum coherence: Physical limits and pulse sequences

    NASA Astrophysics Data System (ADS)

    Köcher, S. S.; Heydenreich, T.; Zhang, Y.; Reddy, G. N. M.; Caldarelli, S.; Yuan, H.; Glaser, S. J.

    2016-04-01

    Here we study the optimum efficiency of the excitation of maximum quantum (MaxQ) coherence using analytical and numerical methods based on optimal control theory. The theoretical limit of the achievable MaxQ amplitude and the minimum time to achieve this limit are explored for a set of model systems consisting of up to five coupled spins. In addition to arbitrary pulse shapes, two simple pulse sequence families of practical interest are considered in the optimizations. Compared to conventional approaches, substantial gains were found both in terms of the achieved MaxQ amplitude and in pulse sequence durations. For a model system, theoretically predicted gains of a factor of three compared to the conventional pulse sequence were experimentally demonstrated. Motivated by the numerical results, also two novel analytical transfer schemes were found: Compared to conventional approaches based on non-selective pulses and delays, double-quantum coherence in two-spin systems can be created twice as fast using isotropic mixing and hard spin-selective pulses. Also it is proved that in a chain of three weakly coupled spins with the same coupling constants, triple-quantum coherence can be created in a time-optimal fashion using so-called geodesic pulses.

  19. The quantum correlation dynamics of two qubits in finite-temperature environments with dynamical decoupling pulses

    SciTech Connect

    He, Qi-Liang; Xu, Jing-Bo; Yao, Dao-Xin; Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996 ; Zhang, Ye-Qi

    2013-07-15

    We investigate the dynamics of quantum correlation between two noninteracting qubits each inserted in its own finite-temperature environment with 1/f spectral density. It is found that the phenomenon of sudden transition between classical and quantum decoherence exists in the system when two qubits are initially prepared in X-type quantum states, and the transition time depends on the initial-state of two qubits, the qubit–environment coupling constant and the temperature of the environment. Furthermore, we explore the influence of dynamical decoupling pulses on the transition time and show that it can be prolonged by applying the dynamical decoupling pulses. -- Highlights: •The sudden transition phenomenon from finite-temperature environments is studied. •The transition time depends on the environment temperature and the system parameters. •The transition time can be prolonged by applying the dynamical decoupling pulses.

  20. Coherent-pulse implementations of quantum cryptography protocols resistant to photon-number-splitting attacks

    SciTech Connect

    Acin, Antonio; Gisin, Nicolas; Scarani, Valerio

    2004-01-01

    We propose a class of quantum cryptography protocols that are robust against photon-number-splitting attacks (PNS) in a weak coherent-pulse implementation. We give a quite exhaustive analysis of several eavesdropping attacks on these schemes. The honest parties (Alice and Bob) use present-day technology, in particular an attenuated laser as an approximation of a single-photon source. The idea of the protocols is to exploit the nonorthogonality of quantum states to decrease the information accessible to Eve due to the multiphoton pulses produced by the imperfect source. The distance at which the key distribution becomes insecure due to the PNS attack is significantly increased compared to the existing schemes. We also show that strong-pulse implementations, where a strong pulse is included as a reference, allow for key distribution robust against photon-number-splitting attacks.

  1. Femtosecond strong-field quantum control with sinusoidally phase-modulated pulses

    SciTech Connect

    Wollenhaupt, M.; Praekelt, A.; Sarpe-Tudoran, C.; Liese, D.; Bayer, T.; Baumert, T.

    2006-06-15

    The quantum control of the ionization of potassium atoms using shaped intense femtosecond laser pulses is investigated. We use sinusoidal phase modulation as a prototype for complex shaped pulses to investigate the physical mechanism of the strong-field quantum control by shaped femtosecond light fields. The influence of all parameters characterizing the sinusoidal phase modulation on strong-field-induced dynamics is studied systematically in experiment and theory. Our results are interpreted in terms of the selective population of dressed states (SPODS) which gives a natural physical picture of the dynamics in intense laser fields. We show that modulated femtosecond pulses in combination with photoelectron spectroscopy are a versatile tool to prepare and to probe SPODS. The decomposition of the excitation and ionization process induced by shaped pulses into elementary physically transparent steps is discussed.

  2. Magnetic Flux Effect on a Kondo-Induced Electric Polarization in a Triangular Triple Quantum Dot

    NASA Astrophysics Data System (ADS)

    Koga, Mikito; Matsumoto, Masashige; Kusunose, Hiroaki

    2014-08-01

    A magnetic flux effect is studied theoretically on an electric polarization induced by the Kondo effect in a triangular triple-quantum-dot system, where one of the three dots is connected to a metallic lead. This electric polarization exhibits an Aharonov-Bohm oscillation as a function of the magnetic flux penetrating through the triangular loop. The numerical renormalization group analysis reveals how the oscillation pattern depends on the Kondo coupling of a local spin with lead electrons, which is sensitive to the point contact with the lead. It provides an experimental implication that the Kondo effect is the origin of the emergent electric polarization.

  3. Kondo-induced electric polarization modulated by magnetic flux through a triangular triple quantum dot

    NASA Astrophysics Data System (ADS)

    Koga, M.; Matsumoto, M.; Kusunose, H.

    2015-03-01

    The Kondo effect plays an important role in emergence of electric polarization in a triangular triple-quantum-dot system, where one of the three dots is point-contacted with a single lead, and a magnetic flux penetrates through the triangular loop. The Kondo-induced electric polarization exhibits an Aharonov-Bohm type oscillation as a function of the magnetic flux. Our theoretical study shows various oscillation patterns associated with the field-dependent mixing of twofold orbitally degenerate ground states and their sensitivity to the point contact.

  4. Proposal for geometric generation of a biexciton in a quantum dot using a chirped pulse

    SciTech Connect

    Hui, H. Y.; Liu, R. B.

    2008-10-15

    We propose to create a biexciton in a quantum dot by a coherent optical process using a frequency-sweeping (chirped) laser pulse. In contrast to the two-photon Rabi flop scheme, the present method uses the adiabatic state transfer through avoided level crossing. As a geometric control, the proposed process is robust against pulse area uncertainty, detuning, and dephasing. The speed of the adiabatic operation is constrained by the biexciton binding energy.

  5. Coalescence-controlled and coalescence-free growth regimes during deposition of pulsed metal vapor fluxes on insulating surfaces

    SciTech Connect

    Lü, B.; Münger, E. P.; Sarakinos, K.

    2015-04-07

    The morphology and physical properties of thin films deposited by vapor condensation on solid surfaces are predominantly set by the processes of island nucleation, growth, and coalescence. When deposition is performed using pulsed vapor fluxes, three distinct nucleation regimes are known to exist depending on the temporal profile of the flux. These regimes can be accessed by tuning deposition conditions; however, their effect on film microstructure becomes marginal when coalescence sets in and erases morphological features obtained during nucleation. By preventing coalescence from being completed, these nucleation regimes can be used to control microstructure evolution and thus access a larger palette of film morphological features. Recently, we derived the quantitative criterion to stop coalescence during continuous metal vapor flux deposition on insulating surfaces—which typically yields 3-dimensional growth—by describing analytically the competition between island growth by atomic incorporation and the coalescence rate of islands [Lü et al., Appl. Phys. Lett. 105, 163107 (2014)]. Here, we develop the analytical framework for entering a coalescence-free growth regime for metal vapor deposition on insulating substrates using pulsed vapor fluxes, showing that there exist three distinct criteria for suppressing coalescence that correspond to the three nucleation regimes of pulsed vapor flux deposition. The theoretical framework developed herein is substantiated by kinetic Monte Carlo growth simulations. Our findings highlight the possibility of using atomistic nucleation theory for pulsed vapor deposition to control morphology of thin films beyond the point of island density saturation.

  6. Pulse-controlled quantum gate sequences on a strongly coupled qubit chain

    NASA Astrophysics Data System (ADS)

    Frydrych, Holger; Marthaler, Michael; Alber, Gernot

    2015-12-01

    We propose a selective dynamical decoupling scheme on a chain of permanently coupled qubits with XX-type interactions, which is capable of dynamically suppressing any coupling in the chain by applying sequences of local pulses to the individual qubits. We demonstrate that high-fidelity single- and two-qubit gates can be achieved by this procedure and that sequences of gates can be implemented by this pulse control alone. We discuss the applicability and physical limitations of our model specifically for strongly coupled superconducting flux qubits. Since dynamically modifying the couplings between flux qubits is challenging, they are a natural candidate for our approach.

  7. Retrieval of original signals for superconducting quantum interference device operating in flux locked mode

    NASA Astrophysics Data System (ADS)

    Liu, Dang-Ting; Tian, Ye; Zhao, Shi-Ping; Ren, Yu-Feng; Chen, Geng-Hua

    2015-04-01

    We discuss a simple relation between the input and output signals of a superconducting quantum interference device magnetometer operating in flux locked mode in a cosine curve approximation. According to this relation, an original fast input signal can be easily retrieved from its distorted output response. This technique can be used in some areas such as sensitive and fast detection of magnetic or metallic grains in medicine and food security checking.

  8. Protection of dissipative quantum state preparation by interlacing the control with dynamical decoupling pulses

    NASA Astrophysics Data System (ADS)

    Gong, Z. R.; Yao, Wang

    2012-02-01

    Various dissipative processes have recently be exploited for preparing quantum state with multipartite entanglement between many qubits. Most such schemes are applicable only to an ensemble of identical qubits, and inhomogeneous broadening will reduce the state preparation fidelity. Here we show that by interlacing the dynamical decoupling pulse sequence with the dissipative state preparation control, the errors resulting from the inhomogeneous broadening can be suppressed up to certain order of the pulse interval and the desired entangled states can be prepared with high fidelity. We give two examples where sequence of pi pulses interlaced with dissipative control realize high fidelity preparation of cluster states and many-body singlets of atomic qubits.

  9. Monolithic colliding-pulse mode-locked quantum-well lasers

    SciTech Connect

    Chen, Youngkai; Wu, M.C. )

    1992-10-01

    Integration of the whole mode-locked laser onto a single piece of semiconductor offers a number of advantages, including total elimination of optical alignment processes, improved mechanical stability, and the generation of short optical pulses at much higher repetition frequencies. Semiconductor laser processing technologies were used to implement the colliding-pulse mode-locking (CPM) scheme, which is known to effectively shorten the pulses and increase stability, on a miniature monolithic semiconductor cavity. The principles of and recent progress in monolithic CPM quantum-well lasers are reviewed. 46 refs.

  10. Robust quantum control using smooth pulses and topological winding

    PubMed Central

    Barnes, Edwin; Wang, Xin; Das Sarma, S.

    2015-01-01

    The greatest challenge in achieving the high level of control needed for future technologies based on coherent quantum systems is the decoherence induced by the environment. Here, we present an analytical approach that yields explicit constraints on the driving field which are necessary and sufficient to ensure that the leading-order noise-induced errors in a qubit’s evolution cancel exactly. We derive constraints for two of the most common types of noise that arise in qubits: slow fluctuations of the qubit energy splitting and fluctuations in the driving field itself. By theoretically recasting a phase in the qubit’s wavefunction as a topological winding number, we can satisfy the noise-cancelation conditions by adjusting driving field parameters without altering the target state or quantum evolution. We demonstrate our method by constructing robust quantum gates for two types of spin qubit: phosphorous donors in silicon and nitrogen-vacancy centers in diamond. PMID:26239195

  11. Eddy covariance carbonyl sulfide flux measurements with a quantum cascade laser absorption spectrometer

    NASA Astrophysics Data System (ADS)

    Gerdel, Katharina; Spielmann, Felix M.; Hammerle, Albin; Wohlfahrt, Georg

    2016-04-01

    Carbonyl sulfide (COS) is the most abundant sulfur containing trace gas present in the troposphere at concentrations of around 500 ppt. Recent interest in COS by the ecosystem-physiological community has been sparked by the fact that COS co-diffuses into plant leaves pretty much the same way as carbon dioxide (CO2) does, but in contrast to CO2, COS is not known to be emitted by plants. Thus uptake of COS by vegetation has the potential to be used as a tracer for canopy gross photosynthesis, which cannot be measured directly, however represents a key term in the global carbon cycle. Since a few years, quantum cascade laser absorption spectrometers (QCLAS) are commercially available with the precision, sensitivity and time response suitable for eddy covariance (EC) flux measurements. While there exist a handful of published reports on EC flux measurements in the recent literature, no rigorous investigation of the applicability of QCLAS for EC COS flux measurements has been carried out so far, nor have been EC processing and QA/QC steps developed for carbon dioxide and water vapor flux measurements within FLUXNET been assessed for COS. The aim of this study is to close this knowledge gap, to discuss critical steps in the post-processing chain of COS EC flux measurements and to devise best-practice guidelines for COS EC flux data processing. To this end we collected EC COS (and CO2, H2O and CO) flux measurements above a temperate mountain grassland in Austria over the vegetation period 2015 with a commercially available QCLAS. We discuss various aspects of EC data post-processing, in particular issues with the time-lag estimation between sonic anemometer and QCLAS signals and QCLAS time series detrending, as well as QA/QC, in particular flux detection limits, random flux uncertainty, the interaction of various processing steps with common EC QA/QC filters (e.g. detrending and stationarity tests), u*-filtering, etc.

  12. Quantum entanglement and teleportation in pulsed cavity optomechanics

    SciTech Connect

    Hofer, Sebastian G.; Wieczorek, Witlef; Aspelmeyer, Markus; Hammerer, Klemens

    2011-11-15

    Entangling a mechanical oscillator with an optical mode is an enticing and yet a very challenging goal in cavity optomechanics. Here we consider a pulsed scheme to create Einstein-Podolsky-Rosen-type entanglement between a traveling-wave light pulse and a mechanical oscillator. The entanglement can be verified unambiguously by a pump-probe sequence of pulses. In contrast to schemes that work in a steady-state regime under a continuous-wave drive, this protocol is not subject to stability requirements that normally limit the strength of achievable entanglement. We investigate the protocol's performance under realistic conditions, including mechanical decoherence, in full detail. We discuss the relevance of a high mechanical Qf product for entanglement creation and provide a quantitative statement on which magnitude of the Qf product is necessary for a successful realization of the scheme. We determine the optimal parameter regime for its operation and show it to work in current state-of-the-art systems.

  13. Repeated pulses of vertical methane flux recorded in glacial sediments from the southeast Bering Sea

    NASA Astrophysics Data System (ADS)

    Cook, Mea S.; Keigwin, Lloyd D.; Birgel, Daniel; Hinrichs, Kai-Uwe

    2011-06-01

    There is controversy over the role of marine methane hydrates in atmospheric methane concentrations and climate change during the last glacial period. In this study of two sediment cores from the southeast Bering Sea (700 m and 1467 m water depth), we identify multiple episodes during the last glacial period of intense methane flux reaching the seafloor. Within the uncertainty of the radiocarbon age model, the episodes are contemporaneous in the two cores and have similar timing and duration as Dansgaard-Oeschger events. The episodes are marked by horizons of sediment containing 13C-depleted authigenic carbonate minerals; 13C-depleted archaeal and bacterial lipids, which resemble those found in ANME-1 type anaerobic methane oxidizing microbial consortia; and changes in the abundance and species distribution of benthic foraminifera. The similar timing and isotopic composition of the authigenic carbonates in the two cores is consistent with a region-wide increase in the upward flux of methane bearing fluids. This study is the first observation outside Santa Barbara Basin of pervasive, repeated methane flux in glacial sediments. However, contrary to the "Clathrate Gun Hypothesis" (Kennett et al., 2003), these coring sites are too deep for methane hydrate destabilization to be the cause, implying that a much larger part of the ocean's sedimentary methane may participate in climate or carbon cycle feedback at millennial timescales. We speculate that pulses of methane in these opal-rich sediments could be caused by the sudden release of overpressure in pore fluids that builds up gradually with silica diagenesis. The release could be triggered by seismic shaking on the Aleutian subduction zone caused by hydrostatic pressure increase associated with sea level rise at the start of interstadials.

  14. Optical pulse dynamics for quantum-dot logic operations in a photonic-crystal waveguide

    SciTech Connect

    Ma, Xun; John, Sajeev

    2011-11-15

    We numerically demonstrate all-optical logic operations with quantum dots (QDs) embedded in a bimodal photonic-crystal waveguide using Maxwell-Bloch equations in a slowly varying envelope approximation (SVEA). The two-level QD excitation level is controlled by one or more femtojoule optical driving pulses passing through the waveguide. Specific logic operations depend on the relative pulse strengths and their detunings from an inhomogeneouslly broadened (about 1% for QD transitions centered at 1.5 {mu}m) QD transition. This excitation controlled two-level medium then determines passage of subsequent probe optical pulses. Envelope equations for electromagnetic waves in the linear dispersion and cutoff waveguide modes are derived to simplify solution of the coupled Maxwell-Bloch equations in the waveguide. These determine the quantum mechanical evolution of the QD excitation and its polarization, driven by classical electromagnetic (EM) pulses near a sharp discontinuity in the EM density of states of the bimodal waveguide. Different configurations of the driving pulses lead to distinctive relations between driving pulse strength and probe pulse passage, representing all-optical logic and, or, and not operations. Simulation results demonstrate that such operations can be done on picosecond time scales and within a waveguide length of about 10 {mu}m in a photonic-band-gap (PBG) optical microchip.

  15. Quantum switching of π-electron rotations in a nonplanar chiral molecule by using linearly polarized UV laser pulses.

    PubMed

    Mineo, Hirobumi; Yamaki, Masahiro; Teranishi, Yoshiaki; Hayashi, Michitoshi; Lin, Sheng Hsien; Fujimura, Yuichi

    2012-09-01

    Nonplanar chiral aromatic molecules are candidates for use as building blocks of multidimensional switching devices because the π electrons can generate ring currents with a variety of directions. We employed (P)-2,2'-biphenol because four patterns of π-electron rotations along the two phenol rings are possible and theoretically determine how quantum switching of the π-electron rotations can be realized. We found that each rotational pattern can be driven by a coherent excitation of two electronic states under two conditions: one is the symmetry of the electronic states and the other is their relative phase. On the basis of the results of quantum dynamics simulations, we propose a quantum control method for sequential switching among the four rotational patterns that can be performed by using ultrashort overlapped pump and dump pulses with properly selected relative phases and photon polarization directions. The results serve as a theoretical basis for the design of confined ultrafast switching of ring currents of nonplanar molecules and further current-induced magnetic fluxes of more sophisticated systems. PMID:22889209

  16. Controlling pathway dynamics of a four-level quantum system with pulse shaping

    NASA Astrophysics Data System (ADS)

    Cao, Dewen; Yang, Ling; Wang, Yaoxiong; Shuang, Feng; Gao, Fang

    2016-07-01

    The dynamics of two two-photon absorption (TPA) pathways in a four-level quantum system driven by a laser pulse is investigated in this work. An analytical solution for pulse shaping is proposed to be globally optimal for constructive interference between the two pathways, and accurate spectral boundaries for phase modulation are obtained. The TPA rate can be enhanced by a factor of 8.33 with the optimal pulse instead of the transform limited pulse (TL pulse). Simple control strategies modulating both amplitudes and phases are also designed to increase the TPA amplitude along one pathway while decreasing that along the other simultaneously. The strategies are intuitive and the two pathway amplitudes can differ by two orders of magnitude.

  17. Comparison of the quantum and classical calculations of flux density of (220) channeled positrons in Si crystal

    NASA Astrophysics Data System (ADS)

    Korotchenko, K. B.; Tukhfatullin, TA; Pivovarov, Yu L.; Eikhorn, Yu L.

    2016-07-01

    Simulation of flux-peaking effect of the 255 MeV positrons channeled in (220) Si crystals is performed in the frame of classical and quantum mechanics. Comparison of the results obtained using both approaches shows relatively good agreement.

  18. Wavelength-dependent femtosecond pulse amplification in wideband tapered-waveguide quantum well semiconductor optical amplifiers.

    PubMed

    Xia, Mingjun; Ghafouri-Shiraz, H

    2015-12-10

    In this paper, we study the wavelength-dependent amplification in three different wideband quantum well semiconductor optical amplifiers (QWAs) having conventional, exponentially tapered, and linearly tapered active region waveguide structures. A new theoretical model for tapered-waveguide QWAs considering the effect of lateral carrier density distribution and the strain effect in the quantum well is established based on a quantum well transmission line modeling method. The temporal and spectral characteristics of amplified femtosecond pulse are analyzed for each structure. It was found that, for the amplification of a single femtosecond pulse, the tapered-waveguide QWA provides higher saturation gain, and the output spectra of the amplified pulse in all three structures exhibit an apparent redshift and bandwidth narrowing due to the reduction of carrier density; however, the output spectrum in the tapered-waveguide amplifier is less distorted and exhibits smaller bandwidth narrowing. For the simultaneous amplification of two femtosecond pulses with different central frequencies, in all the three structures, two peaks appear in the output spectra while the peak at the frequency closer to the peak frequency of the QWA gain spectrum receives higher amplification due to the frequency (wavelength) dependence of the QWA gain. At a low peak power level of the input pulse, the bandwidth of each window in the tapered structure is larger than that of the conventional waveguide structure, which aggravates the spectrum alias in the amplification of femtosecond pulses with different central frequencies. As the peak powers of the two pulses increase, the spectrum alias in the conventional waveguide becomes more serious while there are small changes in the tapered structures. Also, we have found that in the amplification of a femtosecond pulse train, the linear-tapered QWAs exhibit the fastest gain recovery as compared with the conventional and exponentially tapered QWAs. PMID

  19. Kinetics of pulse-induced photoluminescence from a semiconductor quantum dot.

    PubMed

    Rukhlenko, Ivan D; Leonov, Mikhail Yu; Turkov, Vadim K; Litvin, Aleksandr P; Baimuratov, Anvar S; Baranov, Alexander V; Fedorov, Anatoly V

    2012-12-01

    Optical methods, which allow the determination of the dominant channels of energy and phase relaxation, are the most universal techniques for the investigation of semiconductor quantum dots. In this paper, we employ the kinetic Pauli equation to develop the first generalized model of the pulse-induced photoluminescence from the lowest-energy eigenstates of a semiconductor quantum dot. Without specifying the shape of the excitation pulse and by assuming that the energy and phase relaxation in the quantum dot may be characterized by a set of phenomenological rates, we derive an expression for the observable photoluminescence cross section, valid for an arbitrary number of the quantum dot's states decaying with the emission of secondary photons. Our treatment allows for thermal transitions occurring with both decrease and increase in energy between all the relevant eigenstates at room or higher temperature. We show that in the general case of N states coupled to each other through a bath, the photoluminescence kinetics from any of them is determined by the sum of N exponential functions, whose exponents are proportional to the respective decay rates. We illustrate the application of the developed model by considering the processes of resonant luminescence and thermalized luminescence from the quantum dot with two radiating eigenstates, and by assuming that the secondary emission is excited with either a Gaussian or exponential pulse. Analytic expressions describing the signals of secondary emission are analyzed, in order to elucidate experimental situations in which the relaxation constants may be reliably extracted from the photoluminescence spectra. PMID:23262711

  20. Quantum control of multilevel atoms with rotational degeneracy using short laser pulses

    SciTech Connect

    Demeter, G.

    2010-10-15

    We study the quantum control of multilevel atoms with rotationally degenerate levels using short laser pulses. Various control schemes are considered, ones using {pi} pulses, frequency-chirped pulses, two consecutive pulses, or two pulses that overlap each other partially. We study the possibilities of controlling the quantum state of an ensemble of atoms distributed randomly over one or more rotationally degenerate levels initially. For the sake of concreteness we use the hyperfine level scheme of the {sup 85}Rb D line, but the results can easily be generalized for any of the alkali-metal atoms used in cooling and trapping experiments. We find that even though a number of difficulties arise, such as unequal coupling constants between rotational sublevels or dephasing between different hyperfine levels during the interaction, control schemes using simple or multiphoton adiabatic passage can be used to control the internal states of the atoms effectively as well as the center-of-mass motion. Furthermore, it is shown that in some cases it is possible to exploit the inequality of the coupling constants to entangle the rotational substates with specific distinct translational quantum states and hence separate these substates in momentum space.

  1. Implementing and diagnosing magnetic flux compression on the Z pulsed power accelerator

    SciTech Connect

    McBride, Ryan D.; Bliss, David E.; Gomez, Matthew R.; Hansen, Stephanie B.; Martin, Matthew R.; Jennings, Christopher Ashley; Slutz, Stephen A.; Rovang, Dean C.; Knapp, Patrick F.; Schmit, Paul F.; Awe, Thomas James; Hess, M. H.; Lemke, Raymond W.; Dolan, D. H.; Lamppa, Derek C.; Jobe, Marc Ronald Lee; Fang, Lu; Hahn, Kelly D.; Chandler, Gordon A.; Cooper, Gary Wayne; Ruiz, Carlos L.; Maurer, A. J.; Robertson, Grafton Kincannon; Cuneo, Michael E.; Sinars, Daniel; Tomlinson, Kurt; Smith, Gary; Paguio, Reny; Intrator, Tom; Weber, Thomas; Greenly, John

    2015-11-01

    We report on the progress made to date for a Laboratory Directed Research and Development (LDRD) project aimed at diagnosing magnetic flux compression on the Z pulsed-power accelerator (0-20 MA in 100 ns). Each experiment consisted of an initially solid Be or Al liner (cylindrical tube), which was imploded using the Z accelerator's drive current (0-20 MA in 100 ns). The imploding liner compresses a 10-T axial seed field, B z ( 0 ) , supplied by an independently driven Helmholtz coil pair. Assuming perfect flux conservation, the axial field amplification should be well described by B z ( t ) = B z ( 0 ) x [ R ( 0 ) / R ( t )] 2 , where R is the liner's inner surface radius. With perfect flux conservation, B z ( t ) and dB z / dt values exceeding 10 4 T and 10 12 T/s, respectively, are expected. These large values, the diminishing liner volume, and the harsh environment on Z, make it particularly challenging to measure these fields. We report on our latest efforts to do so using three primary techniques: (1) micro B-dot probes to measure the fringe fields associated with flux compression, (2) streaked visible Zeeman absorption spectroscopy, and (3) fiber-based Faraday rotation. We also mention two new techniques that make use of the neutron diagnostics suite on Z. These techniques were not developed under this LDRD, but they could influence how we prioritize our efforts to diagnose magnetic flux compression on Z in the future. The first technique is based on the yield ratio of secondary DT to primary DD reactions. The second technique makes use of the secondary DT neutron time-of-flight energy spectra. Both of these techniques have been used successfully to infer the degree of magnetization at stagnation in fully integrated Magnetized Liner Inertial Fusion (MagLIF) experiments on Z [P. F. Schmit et al. , Phys. Rev. Lett. 113 , 155004 (2014); P. F. Knapp et al. , Phys. Plasmas, 22 , 056312 (2015)]. Finally, we present some recent developments for designing

  2. Various methods of optimizing control pulses for quantum systems with decoherence

    NASA Astrophysics Data System (ADS)

    Pawela, Łukasz; Sadowski, Przemysław

    2016-05-01

    We design control setting that allows the implementation of an approximation of an unitary operation of a quantum system under decoherence using various quantum system layouts and numerical algorithms. We focus our attention on the possibility of adding ancillary qubits which help to achieve a desired quantum map on the initial system. Furthermore, we use three methods of optimizing the control pulses: genetic optimization, approximate evolution method and approximate gradient method. To model the noise in the system we use the Lindblad equation. We obtain results showing that applying the control pulses to the ancilla allows one to successfully implement unitary operation on a target system in the presence of noise, which is not possible which control field applied to the system qubits.

  3. Implementing a quantum cloning machine in separate cavities via the optical coherent pulse as a quantum communication bus

    NASA Astrophysics Data System (ADS)

    Zhu, Meng-Zheng; Ye, Liu

    2015-04-01

    An efficient scheme is proposed to implement a quantum cloning machine in separate cavities based on a hybrid interaction between electron-spin systems placed in the cavities and an optical coherent pulse. The coefficient of the output state for the present cloning machine is just the direct product of two trigonometric functions, which ensures that different types of quantum cloning machine can be achieved readily in the same framework by appropriately adjusting the rotated angles. The present scheme can implement optimal one-to-two symmetric (asymmetric) universal quantum cloning, optimal symmetric (asymmetric) phase-covariant cloning, optimal symmetric (asymmetric) real-state cloning, optimal one-to-three symmetric economical real-state cloning, and optimal symmetric cloning of qubits given by an arbitrary axisymmetric distribution. In addition, photon loss of the qubus beams during the transmission and decoherence effects caused by such a photon loss are investigated.

  4. Curl flux, coherence, and population landscape of molecular systems: Nonequilibrium quantum steady state, energy (charge) transport, and thermodynamics

    SciTech Connect

    Zhang, Z. D.; Wang, J.

    2014-06-28

    We established a theoretical framework in terms of the curl flux, population landscape, and coherence for non-equilibrium quantum systems at steady state, through exploring the energy and charge transport in molecular processes. The curl quantum flux plays the key role in determining transport properties and the system reaches equilibrium when flux vanishes. The novel curl quantum flux reflects the degree of non-equilibriumness and the time-irreversibility. We found an analytical expression for the quantum flux and its relationship to the environmental pumping (non-equilibriumness quantified by the voltage away from the equilibrium) and the quantum tunneling. Furthermore, we investigated another quantum signature, the coherence, quantitatively measured by the non-zero off diagonal element of the density matrix. Populations of states give the probabilities of individual states and therefore quantify the population landscape. Both curl flux and coherence depend on steady state population landscape. Besides the environment-assistance which can give dramatic enhancement of coherence and quantum flux with high voltage at a fixed tunneling strength, the quantum flux is promoted by the coherence in the regime of small tunneling while reduced by the coherence in the regime of large tunneling, due to the non-monotonic relationship between the coherence and tunneling. This is in contrast to the previously found linear relationship. For the systems coupled to bosonic (photonic and phononic) reservoirs the flux is significantly promoted at large voltage while for fermionic (electronic) reservoirs the flux reaches a saturation after a significant enhancement at large voltage due to the Pauli exclusion principle. In view of the system as a quantum heat engine, we studied the non-equilibrium thermodynamics and established the analytical connections of curl quantum flux to the transport quantities such as energy (charge) transfer efficiency, chemical reaction efficiency, energy

  5. SU(3) quantum interferometry with single-photon input pulses.

    PubMed

    Tan, Si-Hui; Gao, Yvonne Y; de Guise, Hubert; Sanders, Barry C

    2013-03-15

    We develop a framework for solving the action of a three-channel passive optical interferometer on single-photon pulse inputs to each channel using SU(3) group-theoretic methods, which can be readily generalized to higher-order photon-coincidence experiments. We show that features of the coincidence plots versus relative time delays of photons yield information about permanents, immanants, and determinants of the interferometer SU(3) matrix. PMID:25166532

  6. Generation of high-photon flux-coherent soft x-ray radiation with few-cycle pulses.

    PubMed

    Demmler, Stefan; Rothhardt, Jan; Hädrich, Steffen; Krebs, Manuel; Hage, Arvid; Limpert, Jens; Tünnermann, Andreas

    2013-12-01

    We present a tabletop source of coherent soft x-ray radiation with high-photon flux. Two-cycle pulses delivered by a fiber-laser-pumped optical parametric chirped-pulse amplifier operating at 180 kHz repetition rate are upconverted via high harmonic generation in neon to photon energies beyond 200 eV. A maximum photon flux of 1.3·10(8) photons/s is achieved within a 1% bandwidth at 125 eV photon energy. This corresponds to a conversion efficiency of ~10(-9), which can be reached due to a gas jet simultaneously providing a high target density and phase matching. Further scaling potential toward higher photon flux as well as higher photon energies are discussed. PMID:24281507

  7. Efficient amplitude-modulated pulses for triple- to single-quantum coherence conversion in MQMAS NMR.

    PubMed

    Colaux, Henri; Dawson, Daniel M; Ashbrook, Sharon E

    2014-08-01

    The conversion between multiple- and single-quantum coherences is integral to many nuclear magnetic resonance (NMR) experiments of quadrupolar nuclei. This conversion is relatively inefficient when effected by a single pulse, and many composite pulse schemes have been developed to improve this efficiency. To provide the maximum improvement, such schemes typically require time-consuming experimental optimization. Here, we demonstrate an approach for generating amplitude-modulated pulses to enhance the efficiency of the triple- to single-quantum conversion. The optimization is performed using the SIMPSON and MATLAB packages and results in efficient pulses that can be used without experimental reoptimisation. Most significant signal enhancements are obtained when good estimates of the inherent radio-frequency nutation rate and the magnitude of the quadrupolar coupling are used as input to the optimization, but the pulses appear robust to reasonable variations in either parameter, producing significant enhancements compared to a single-pulse conversion, and also comparable or improved efficiency over other commonly used approaches. In all cases, the ease of implementation of our method is advantageous, particularly for cases with low sensitivity, where the improvement is most needed (e.g., low gyromagnetic ratio or high quadrupolar coupling). Our approach offers the potential to routinely improve the sensitivity of high-resolution NMR spectra of nuclei and systems that would, perhaps, otherwise be deemed "too challenging". PMID:25047226

  8. Efficient Amplitude-Modulated Pulses for Triple- to Single-Quantum Coherence Conversion in MQMAS NMR

    PubMed Central

    2014-01-01

    The conversion between multiple- and single-quantum coherences is integral to many nuclear magnetic resonance (NMR) experiments of quadrupolar nuclei. This conversion is relatively inefficient when effected by a single pulse, and many composite pulse schemes have been developed to improve this efficiency. To provide the maximum improvement, such schemes typically require time-consuming experimental optimization. Here, we demonstrate an approach for generating amplitude-modulated pulses to enhance the efficiency of the triple- to single-quantum conversion. The optimization is performed using the SIMPSON and MATLAB packages and results in efficient pulses that can be used without experimental reoptimisation. Most significant signal enhancements are obtained when good estimates of the inherent radio-frequency nutation rate and the magnitude of the quadrupolar coupling are used as input to the optimization, but the pulses appear robust to reasonable variations in either parameter, producing significant enhancements compared to a single-pulse conversion, and also comparable or improved efficiency over other commonly used approaches. In all cases, the ease of implementation of our method is advantageous, particularly for cases with low sensitivity, where the improvement is most needed (e.g., low gyromagnetic ratio or high quadrupolar coupling). Our approach offers the potential to routinely improve the sensitivity of high-resolution NMR spectra of nuclei and systems that would, perhaps, otherwise be deemed “too challenging”. PMID:25047226

  9. Surface thermocouples for measurement of pulsed heat flux in the divertor of the Alcator C-Mod tokamak

    SciTech Connect

    Brunner, D.; LaBombard, B.

    2012-03-15

    A novel set of thermocouple sensors has been developed to measure heat fluxes arriving at divertor surfaces in the Alcator C-Mod tokamak, a magnetic confinement fusion experiment. These sensors operate in direct contact with the divertor plasma, which deposits heat fluxes in excess of {approx}10 MW/m{sup 2} over an {approx}1 s pulse. Thermoelectric EMF signals are produced across a non-standard bimetallic junction: a 50 {mu}m thick 74% tungsten-26% rhenium ribbon embedded in a 6.35 mm diameter molybdenum cylinder. The unique coaxial geometry of the sensor combined with its single-point electrical ground contact minimizes interference from the plasma/magnetic environment. Incident heat fluxes are inferred from surface temperature evolution via a 1D thermal heat transport model. For an incident heat flux of 10 MW/m{sup 2}, surface temperatures rise {approx}1000 deg. C/s, corresponding to a heat flux flowing along the local magnetic field of {approx}200 MW/m{sup 2}. Separate calorimeter sensors are used to independently confirm the derived heat fluxes by comparing total energies deposited during a plasma pulse. Langmuir probes in close proximity to the surface thermocouples are used to test plasma-sheath heat transmission theory and to identify potential sources of discrepancies among physical models.

  10. Pulsed-laser micropatterned quantum-dot array for white light source

    NASA Astrophysics Data System (ADS)

    Wang, Sheng-Wen; Lin, Huang-Yu; Lin, Chien-Chung; Kao, Tsung Sheng; Chen, Kuo-Ju; Han, Hau-Vei; Li, Jie-Ru; Lee, Po-Tsung; Chen, Huang-Ming; Hong, Ming-Hui; Kuo, Hao-Chung

    2016-03-01

    In this study, a novel photoluminescent quantum dots device with laser-processed microscale patterns has been demonstrated to be used as a white light emitting source. The pulsed laser ablation technique was employed to directly fabricate microscale square holes with nano-ripple structures onto the sapphire substrate of a flip-chip blue light-emitting diode, confining sprayed quantum dots into well-defined areas and eliminating the coffee ring effect. The electroluminescence characterizations showed that the white light emission from the developed photoluminescent quantum-dot light-emitting diode exhibits stable emission at different driving currents. With a flexibility of controlling the quantum dots proportions in the patterned square holes, our developed white-light emitting source not only can be employed in the display applications with color triangle enlarged by 47% compared with the NTSC standard, but also provide the great potential in future lighting industry with the correlated color temperature continuously changed in a wide range.

  11. Detection of acrolein and acrylonitrile with a pulsed room temperature quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Manne, J.; Jäger, W.; Tulip, J.

    2010-06-01

    We investigated the use of a pulsed, distributed feedback quantum cascade laser centered at 957 cm-1 in combination with an astigmatic Herriot cell with 250 m path length for the detection of acrolein and acrylonitrile. These molecules have been identified as hazardous air-pollutants because of their adverse health effects. The spectrometer utilizes the intra-pulse method, where a linear frequency down-chirp, that is induced when a top-hat current pulse is applied to the laser, is used for sweeping across the absorption line. Up to 450 ns long pulses were used for these measurements which resulted in a spectral window of ~2.2 cm-1. A room temperature mercury-cadmium-telluride detector was used, resulting in a completely cryogen free spectrometer. We demonstrated detection limits of ~3 ppb for acrylonitrile and ~6 ppb for acrolein with ~10 s averaging time. Laser characterization and optimization of the operational parameters for sensitivity improvement are discussed.

  12. Angular Distribution of Tungsten Material and Ion Flux during Nanosecond Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Hussain, M. S.; Dogar, A. H.; Qayyum, A.; Abbasi, S. A.

    2016-01-01

    Tungsten thin films were prepared by pulsed laser deposition (PLD) technique on glass substrates placed at the angles of 0∘ to 70∘ with respect to the target surface normal. Rutherford backscattering Spectrometry (RBS) analysis of the films indicated that about 90% of tungsten material flux is distributed in a cone of 40∘ solid angle while about 54% of it lies even in a narrower cone of 10∘ solid angle. Significant diffusion of tungsten in glass substrate has been observed in the films deposited at smaller angles with respect to target surface normal. Time-of-flight (TOF) measurements performed using Langmuir probe indicated that the most probable ion energy decreases from about 600 to 91eV for variation of θ from 0∘ to 70∘. In general ion energy spread is quite large at all angles investigated here. The enhanced tungsten diffusion in glass substrate observed at smaller angles is most probably due to the higher ion energy and ion assisted recoil implantation of already deposited tungsten.

  13. Magnetic-flux-driven topological quantum phase transition and manipulation of perfect edge states in graphene tube

    PubMed Central

    Lin, S.; Zhang, G.; Li, C.; Song, Z.

    2016-01-01

    We study the tight-binding model for a graphene tube with perimeter N threaded by a magnetic field. We show exactly that this model has different nontrivial topological phases as the flux changes. The winding number, as an indicator of topological quantum phase transition (QPT) fixes at N/3 if N/3 equals to its integer part [N/3], otherwise it jumps between [N/3] and [N/3] + 1 periodically as the flux varies a flux quantum. For an open tube with zigzag boundary condition, exact edge states are obtained. There exist two perfect midgap edge states, in which the particle is completely located at the boundary, even for a tube with finite length. The threading flux can be employed to control the quantum states: transferring the perfect edge state from one end to the other, or generating maximal entanglement between them. PMID:27554930

  14. Rapid single-flux-quantum circuits for low noise mK operation

    NASA Astrophysics Data System (ADS)

    Intiso, Samuel; Pekola, Jukka; Savin, Alexander; Devyatov, Ygor; Kidiyarova-Shevchenko, Anna

    2006-05-01

    Rapid single-flux-quantum (RSFQ) technology has been proposed as control electronics for superconducting quantum bits because of the material and working temperature compatibility. In this work, we consider practical aspects of RSFQ circuit design for low noise low power operation. At the working temperature of 20 mK and operational frequency of 2 GHz, dissipated power per junction is reduced to 25 pW by using 6 µA critical current junctions available at the Hypres and VTT low Jc fabrication process. To limit phonon temperature to 30 mK, a maximum of 40 junctions can be placed on a 5 mm × 5 mm chip. Electron temperature in resistive shunts of Josephson junctions is minimized by use of cooling fins, giving minimum electron temperatures of about 150 mK for the Hypres process and 70 mK for the VTT process.

  15. Quantum magnetic flux lines, BPS vortex zero modes, and one-loop string tension shifts

    NASA Astrophysics Data System (ADS)

    Alonso-Izquierdo, A.; Mateos Guilarte, J.; de la Torre Mayado, M.

    2016-08-01

    Spectral heat kernel/zeta function regularization procedures are employed in this paper to control the divergences arising from vacuum fluctuations of Bogomolnyi-Prasad-Sommerfield vortices in the Abelian Higgs model. Zero modes of vortex fluctuations are the source of difficulties appearing when the standard Gilkey-de Witt expansion is the tool used in the calculations of one-loop shifts of vortex masses and string tensions. A modified GdW expansion is developed to diminish the impact of the infrared divergences due to the vortex zero modes of fluctuation. With this new technique at our disposal we compute the one-loop vortex mass shifts in the planar AHM and the quantum corrections to the string tension of the magnetic flux tubes living in three dimensions. In both cases it is observed that weak repulsive forces surge between these classically noninteracting topological defects caused by vacuum quantum fluctuations.

  16. Coherent mesoscopic transport through a quantum-dot embedded carbon nanotube ring threaded with magnetic flux

    NASA Astrophysics Data System (ADS)

    Zhao, Hong-Kang; Wang, Jian

    2004-03-01

    We have investigated the coherent mesoscopic transport through a quantum-dot (QD) embedded carbon nanotube ring (CNR) by employing the nonequilibrium Green's function (NGF) technique. The Landauer-Büttiker-like formula is presented to calculate the differential conductance and current-voltage characteristics. Due to the interference of the electrons transporting in the two paths of CNR, the resultant conductivity of electron through the system is determined by the compound concrete structure of CNR-QD system. The tunneling current appears quantum behavior obviously in the small region of source-drain bias. The conductance is adjusted by the gate voltage Vg and the magnetic flux φ. The reversal resonance has been displayed versus the gate voltage, and it is symmetric about Vg for the type I CNR, but it is asymmetric for the type II CNR. The phase inverse oscillations are also presented for the different types of CNRs.

  17. Giant photon bunching, superradiant pulse emission and excitation trapping in quantum-dot nanolasers

    NASA Astrophysics Data System (ADS)

    Jahnke, Frank; Gies, Christopher; Aßmann, Marc; Bayer, Manfred; Leymann, H. A. M.; Foerster, Alexander; Wiersig, Jan; Schneider, Christian; Kamp, Martin; Höfling, Sven

    2016-05-01

    Light is often characterized only by its classical properties, like intensity or coherence. When looking at its quantum properties, described by photon correlations, new information about the state of the matter generating the radiation can be revealed. In particular the difference between independent and entangled emitters, which is at the heart of quantum mechanics, can be made visible in the photon statistics of the emitted light. The well-studied phenomenon of superradiance occurs when quantum-mechanical correlations between the emitters are present. Notwithstanding, superradiance was previously demonstrated only in terms of classical light properties. Here, we provide the missing link between quantum correlations of the active material and photon correlations in the emitted radiation. We use the superradiance of quantum dots in a cavity-quantum electrodynamics laser to show a direct connection between superradiant pulse emission and distinctive changes in the photon correlation function. This directly demonstrates the importance of quantum-mechanical correlations and their transfer between carriers and photons in novel optoelectronic devices.

  18. Giant photon bunching, superradiant pulse emission and excitation trapping in quantum-dot nanolasers.

    PubMed

    Jahnke, Frank; Gies, Christopher; Aßmann, Marc; Bayer, Manfred; Leymann, H A M; Foerster, Alexander; Wiersig, Jan; Schneider, Christian; Kamp, Martin; Höfling, Sven

    2016-01-01

    Light is often characterized only by its classical properties, like intensity or coherence. When looking at its quantum properties, described by photon correlations, new information about the state of the matter generating the radiation can be revealed. In particular the difference between independent and entangled emitters, which is at the heart of quantum mechanics, can be made visible in the photon statistics of the emitted light. The well-studied phenomenon of superradiance occurs when quantum-mechanical correlations between the emitters are present. Notwithstanding, superradiance was previously demonstrated only in terms of classical light properties. Here, we provide the missing link between quantum correlations of the active material and photon correlations in the emitted radiation. We use the superradiance of quantum dots in a cavity-quantum electrodynamics laser to show a direct connection between superradiant pulse emission and distinctive changes in the photon correlation function. This directly demonstrates the importance of quantum-mechanical correlations and their transfer between carriers and photons in novel optoelectronic devices. PMID:27161302

  19. Effects of Detuning on Control of Intersubband Quantum Well Transitions with Chirped Electromagnetic Pulses

    SciTech Connect

    Blekos, Konstantinos; Terzis, Andreas F.; Simserides, Constantinos; Paspalakis, Emmanuel

    2010-11-10

    We study the interaction of a chirped electromagnetic pulse with intersubband transitions of a double semiconductor quantum well. We specifically consider the interaction of the ground and first excited subbands with the electromagnetic field and use the nonlinear density matrix equations for the description of the system dynamics. These equations are solved numerically for various values of the electron sheet density for a realistic double GaAs/AlGaAs quantum well, and the efficiency of population transfer is discussed with emphasis given to the effects of the detuning of the central frequency of the electromagnetic field from resonance.

  20. High-resolution emission spectra of pulsed terahertz quantum-cascade lasers

    SciTech Connect

    Ikonnikov, A. V. Antonov, A. V.; Lastovkin, A. A.; Gavrilenko, V. I.; Sadof'ev, Yu. G.; Samal, N.

    2010-11-15

    The spectra of pulsed terahertz quantum-cascade lasers were measured with high spectral resolution. The characteristic line width at half maximum was 0.01 cm{sup -1}; it is controlled by laser temperature variations during the supply voltage pulse. It was shown that an increase in the laser temperature leads to a decrease in the emission frequency, which is caused by an increase in the effective refractive index of the active region. It was also found that a decrease in the supply voltage results in a decrease in the emission frequency, which is caused by a change in the energy of diagonal transitions between lasing levels.

  1. Time-bin entangled qubits for quantum communication created by femtosecond pulses

    SciTech Connect

    Marcikic, I.; Riedmatten, H. de; Scarani, V.; Zbinden, H.; Gisin, N.; Tittel, W.

    2002-12-01

    We create pairs of nondegenerate time-bin entangled photons at telecom wavelengths with ultrashort pump pulses. Entanglement is shown by performing Bell kind tests of the Franson type with visibilities of up to 91%. As time-bin entanglement can easily be protected from decoherence as encountered in optical fibers, this experiment opens the road for complex quantum communication protocols over long distances. We also investigate the creation of more than one photon pair in a laser pulse and present a simple tool to quantify the probability of such events to happen.

  2. Control of mixed-state quantum systems by a train of short pulses

    NASA Astrophysics Data System (ADS)

    Sugny, D.; Keller, A.; Atabek, O.; Daems, D.; Dion, C. M.; Guérin, S.; Jauslin, H. R.

    2005-09-01

    A density matrix approach is developed for the control of a mixed-state quantum system using a time-dependent external field such as a train of pulses. This leads to the definition of a target density matrix constructed in a reduced Hilbert space as a specific combination of the eigenvectors of a given observable through weighting factors related to the initial statistics of the system. A train of pulses is considered as a possible strategy to reach this target. An illustration is given by considering the laser control of molecular alignment and orientation in thermal equilibrium.

  3. Pulse propagation and optically controllable switch in coupled semiconductor-double-quantum-dot nanostructures

    NASA Astrophysics Data System (ADS)

    Hamedi, H. R.

    2016-05-01

    The problem of pulse propagation is theoretically investigated through a coupled semiconductor-double-quantum-dot (SDQD) nanostructure. Solving the coupled Maxwell-Bloch equations for the SDQD and field simultaneously, the dynamic control of pulse propagation through the medium is numerically explored. It is found that when all the control fields are in exact resonance with their corresponding transitions, a weak Gaussian-shaped probe pulse is transmitted through the medium nearly without any significant absorption and losses so that it can preserve its shape for quite a long propagation distance. In contrast, when one of the control fields is not in resonance with its corresponding transition, the probe pulse will be absorbed by the QD medium after a short distance. Then we consider the probe pulses with higher intensities. It is realized that an intense probe pulse experiences remarkable absorption and broadening during propagation. Finally, we demonstrate that this SDQD system can be employed as an optically controllable switch for the wave propagation to transit from an absorbing phase to a perfect transparency for the probe field. The required time for such switch is also estimated through realistic values.

  4. Investigation of giant Kerr nonlinearity in quantum cascade lasers using mid-infrared femtosecond pulses

    SciTech Connect

    Cai, Hong; Liu, Sheng; Lalanne, Elaine; Johnson, Anthony M.

    2015-02-02

    We study the Kerr nonlinearity of quantum cascade lasers (QCLs) by coupling resonant and off-resonant mid-infrared (mid-IR) femtosecond (fs) pulses into an active QCL waveguide. We observe an increase in the spectral width of the transmitted fs pulses as the coupled mid-infrared (mid-IR) pulse power increases. This is explained by the self-phase modulation effect due to the large Kerr nonlinearity of QCL waveguides. We further confirm this effect by observing the intensity dependent far-field profile of the transmitted mid-IR pulses, showing the pulses undergo self-focusing as they propagate through the active QCL due to the intensity dependent refractive index. We experimentally estimate the nonlinear refractive index n{sub 2} of a QCL to be ∼8 × 10{sup −9 }cm{sup 2}/W using the far-field beam profile of the transmitted pulses. The finite-difference time-domain simulations of QCL waveguides with Kerr nonlinearity incorporated show similar behavior to the experimental results.

  5. Operation of a Wideband Terahertz Superconducting Bolometer Responding to Quantum Cascade Laser Pulses

    NASA Astrophysics Data System (ADS)

    Cibella, S.; Beck, M.; Carelli, P.; Castellano, M. G.; Chiarello, F.; Faist, J.; Leoni, R.; Ortolani, M.; Sabbatini, L.; Scalari, G.; Torrioli, G.; Turcinkova, D.

    2012-06-01

    We make use of a niobium film to produce a micrometric vacuum-bridge superconducting bolometer responding to THz frequency. The bolometer works anywhere in the temperature range 2-7 K, which can be easily reached in helium bath cryostats or closed-cycle cryocoolers. In this work the bolometer is mounted on a pulse tube refrigerator and operated to measure the equivalent noise power (NEP) and the response to fast (μs) terahertz pulses. The NEP above 100 Hz equals that measured in a liquid helium cryostat showing that potential drawbacks related to the use of a pulse tube refrigerator (like mechanical and thermal oscillations, electromagnetic interference, noise) are irrelevant. At low frequency, instead, the pulse tube expansion-compression cycles originate lines at 1 Hz and harmonics in the noise spectrum. The bolometer was illuminated with THz single pulses coming either from a Quantum Cascade Laser operating at liquid nitrogen temperature or from a frequency-multiplied electronic oscillator. The response of the bolometer to the single pulses show that the device can track signals with a rise time as fast as about 450 ns.

  6. Plasmon-enhanced terahertz emission in self-assembled quantum dots by femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Carreño, F.; Antón, M. A.; Melle, Sonia; Calderón, Oscar G.; Cabrera-Granado, E.; Cox, Joel; Singh, Mahi R.; Egatz-Gómez, A.

    2014-02-01

    A scheme for terahertz (THz) generation from intraband transition in a self-assembled quantum dot (QD) molecule coupled to a metallic nanoparticle (MNP) is analyzed. The QD structure is described as a three-level atom-like system using the density matrix formalism. The MNP with spherical geometry is considered in the quasistatic approximation. A femtosecond laser pulse creates a coherent superposition of two subbands in the quantum dots and produces localized surface plasmons in the nanoparticle which act back upon the QD molecule via dipole-dipole interaction. As a result, coherent THz radiation with a frequency corresponding to the interlevel spacing can be obtained, which is strongly modified by the presence of the MNP. The peak value of the terahertz signal is analyzed as a function of nanoparticle's size, the MNP to QD distance, and the area of the applied laser field. In addition, we theoretically demonstrate that the terahertz pulse generation can be effectively controlled by making use of a train of femtosecond laser pulses. We show that by a proper choice of the parameters characterizing the pulse train a huge enhancement of the terahertz signal is obtained.

  7. Restoring photon indistinguishability via pulse and continuous-wave control of solid-state quantum emitters

    NASA Astrophysics Data System (ADS)

    Fotso, Herbert F.; Feiguin, Adrian E.; Awschalom, David D.; Dobrovitski, Viatcheslav V.

    Interference of indistinguishable photons is a central element of many protocols for entangling distant qubits in quantum networks. In spite of great progress in development and applications of solid-state quantum emitters, the entanglement rate remains severely limited. One of the major obstacles is the photon indistinguishability which is greatly reduced by the uncontrollable slow drift of the qubit emission frequency. We investigate several pulse-based and continuous-wave control protocols which suppress the spectral diffusion. We confirm, using both analytics and direct numerical simulations, that these protocols effectively keep the emission at a set target frequency, and explicitly show that the indistinguishability of the emitted photons is restored by the control. We also compare several pulse-based protocols with different pulse timings, and discuss how they affect the emission line and the photon properties. Considering the nitrogen-vacancy centers in diamonds as a convenient example, we demonstrate that both pulse-based and continuous-wave controls can boost the success rate of the long-range entanglement. This work was supported by AFOSR MURI program and The US Department of Energy - Basic Energy Sciences (Contract No. DE-AC02-07CH11358).

  8. Dropout dynamics in pulsed quantum dot lasers due to mode jumping

    SciTech Connect

    Sokolovskii, G. S.; Dudelev, V. V.; Deryagin, A. G.; Novikov, I. I.; Maximov, M. V.; Ustinov, V. M.; Kuchinskii, V. I.; Viktorov, E. A.; Abusaa, M.; Danckaert, J.; Kolykhalova, E. D.; Soboleva, K. K.; Zhukov, A. E.; Sibbett, W.; Rafailov, E. U.; Erneux, T.

    2015-06-29

    We examine the response of a pulse pumped quantum dot laser both experimentally and numerically. As the maximum of the pump pulse comes closer to the excited-state threshold, the output pulse shape becomes unstable and leads to dropouts. We conjecture that these instabilities result from an increase of the linewidth enhancement factor α as the pump parameter comes close to the excitated state threshold. In order to analyze the dynamical mechanism of the dropout, we consider two cases for which the laser exhibits either a jump to a different single mode or a jump to fast intensity oscillations. The origin of these two instabilities is clarified by a combined analytical and numerical bifurcation diagram of the steady state intensity modes.

  9. Widely tuneable scattering-type scanning near-field optical microscopy using pulsed quantum cascade lasers

    SciTech Connect

    Yoxall, Edward Rahmani, Mohsen; Maier, Stefan A.; Phillips, Chris C.; Navarro-Cía, Miguel

    2013-11-18

    We demonstrate the use of a pulsed quantum cascade laser, wavelength tuneable between 6 and 10 μm, with a scattering-type scanning near-field optical microscope (s-SNOM). A simple method for calculating the signal-to-noise ratio (SNR) of the s-SNOM measurement is presented. For pulsed lasers, the SNR is shown to be highly dependent on the degree of synchronization between the laser pulse and the sampling circuitry; in measurements on a gold sample, the SNR is 26 with good synchronization and less than 1 without. Simulations and experimental s-SNOM images, with a resolution of 100 nm, corresponding to λ/80, and an acquisition time of less than 90 s, are presented as proof of concept. They show the change in the field profile of plasmon-resonant broadband antennas when they are excited with wavelengths of 7.9 and 9.5 μm.

  10. Pulse-mode quantum projection synthesis: Effects of mode mismatch on optical state truncation and preparation

    SciTech Connect

    Oezdemir, Sahin Kaya; Koashi, Masato; Miranowicz, Adam; Imoto, Nobuyuki

    2002-11-01

    Quantum projection synthesis can be used for phase-probability-distribution measurement and optical-state truncation and preparation. The method relies on interfering optical light beams, which is a major challenge in experiments performed by pulsed light sources. In the pulsed regime, the time frequency overlap of the interfering light beams has a major impact on the efficiency of the method. In this paper, the pulse-mode projection-synthesis approach is developed, the mode structures of interfering light beams are characterized, and the effect of this overlap on the fidelity of optical-state truncation and preparation is investigated. By introducing the positive-operator-valued measure for the detection events in the scheme, the effect of mode mismatch between the photon-counting detectors and the incident light beams is also presented.

  11. Nature of quantum states created by one photon absorption: pulsed coherent vs pulsed incoherent light.

    PubMed

    Han, Alex C; Shapiro, Moshe; Brumer, Paul

    2013-08-29

    We analyze electronically excited nuclear wave functions and their coherence when subjecting a molecule to the action of natural, pulsed incoherent solar-like light and to that of ultrashort coherent light assumed to have the same center frequencies and spectral bandwidths. Specifically, we compute the spatiotemporal dependence of the excited wave packets and their electronic coherence for these two types of light sources, on different electronic potential energy surfaces. The resultant excited state wave functions are shown to be dramatically different, reflecting the light source from which they originated. In addition, electronic coherence is found to decay significantly faster for incoherent light than for coherent ultrafast excitation, for both continuum and bound wave packets. These results confirm that the dynamics observed from ultrashort coherent excitation does not reflect what happens in processes induced by solar-like radiation, and conclusions drawn from one do not, in general, apply to the other. These results provide further support to the view that the dynamics observed in studies using ultrashort coherent pulses can be significantly different than those that would result from excitation with natural incoherent light. PMID:23879891

  12. Non-geometric fluxes, quasi-Hopf twist deformations, and nonassociative quantum mechanics

    SciTech Connect

    Mylonas, Dionysios Szabo, Richard J.; Schupp, Peter

    2014-12-15

    We analyse the symmetries underlying nonassociative deformations of geometry in non-geometric R-flux compactifications which arise via T-duality from closed strings with constant geometric fluxes. Starting from the non-abelian Lie algebra of translations and Bopp shifts in phase space, together with a suitable cochain twist, we construct the quasi-Hopf algebra of symmetries that deforms the algebra of functions and the exterior differential calculus in the phase space description of nonassociative R-space. In this setting, nonassociativity is characterised by the associator 3-cocycle which controls non-coassociativity of the quasi-Hopf algebra. We use abelian 2-cocycle twists to construct maps between the dynamical nonassociative star product and a family of associative star products parametrized by constant momentum surfaces in phase space. We define a suitable integration on these nonassociative spaces and find that the usual cyclicity of associative noncommutative deformations is replaced by weaker notions of 2-cyclicity and 3-cyclicity. Using this star product quantization on phase space together with 3-cyclicity, we formulate a consistent version of nonassociative quantum mechanics, in which we calculate the expectation values of area and volume operators, and find coarse-graining of the string background due to the R-flux.

  13. Disclosing hidden information in the quantum Zeno effect: Pulsed measurement of the quantum time of arrival

    NASA Astrophysics Data System (ADS)

    Echanobe, J.; Del Campo, A.; Muga, J. G.

    2008-03-01

    Repeated measurements of a quantum particle to check its presence in a region of space was proposed long ago [G. R. Allcock, Ann. Phys. 53, 286 (1969)] as a natural way to determine the distribution of times of arrival at the orthogonal subspace, but the method was discarded because of the quantum Zeno effect: in the limit of very frequent measurements the wave function is reflected and remains in the original subspace. We show that by normalizing the small bits of arriving (removed) norm, an ideal time distribution emerges in correspondence with a classical local-kinetic-energy distribution.

  14. Direct current superconducting quantum interference device spectrometer for pulsed nuclear magnetic resonance and nuclear quadrupole resonance at frequencies up to 5 MHz

    SciTech Connect

    TonThat, D.M.; Clarke, J. |

    1996-08-01

    A spectrometer based on a dc superconducting quantum interference device (SQUID) has been developed for the direct detection of nuclear magnetic resonance (NMR) or nuclear quadrupole resonance (NQR) at frequencies up to 5 MHz. The sample is coupled to the input coil of the niobium-based SQUID via a nonresonant superconducting circuit. The flux locked loop involves the direct offset integration technique with additional positive feedback in which the output of the SQUID is coupled directly to a low-noise preamplifier. Precession of the nuclear quadrupole spins is induced by a magnetic field pulse with the feedback circuit disabled; subsequently, flux locked operation is restored and the SQUID amplifies the signal produced by the nuclear free induction signal. The spectrometer has been used to detect {sup 27}Al NQR signals in ruby (Al{sub 2}O{sub 3}[Cr{sup 3+}]) at 359 and 714 kHz. {copyright} {ital 1996 American Institute of Physics.}

  15. Giant photon bunching, superradiant pulse emission and excitation trapping in quantum-dot nanolasers

    PubMed Central

    Jahnke, Frank; Gies, Christopher; Aßmann, Marc; Bayer, Manfred; Leymann, H. A. M.; Foerster, Alexander; Wiersig, Jan; Schneider, Christian; Kamp, Martin; Höfling, Sven

    2016-01-01

    Light is often characterized only by its classical properties, like intensity or coherence. When looking at its quantum properties, described by photon correlations, new information about the state of the matter generating the radiation can be revealed. In particular the difference between independent and entangled emitters, which is at the heart of quantum mechanics, can be made visible in the photon statistics of the emitted light. The well-studied phenomenon of superradiance occurs when quantum–mechanical correlations between the emitters are present. Notwithstanding, superradiance was previously demonstrated only in terms of classical light properties. Here, we provide the missing link between quantum correlations of the active material and photon correlations in the emitted radiation. We use the superradiance of quantum dots in a cavity-quantum electrodynamics laser to show a direct connection between superradiant pulse emission and distinctive changes in the photon correlation function. This directly demonstrates the importance of quantum–mechanical correlations and their transfer between carriers and photons in novel optoelectronic devices. PMID:27161302

  16. Model for a pulsed terahertz quantum cascade laser under optical feedback.

    PubMed

    Agnew, Gary; Grier, Andrew; Taimre, Thomas; Lim, Yah Leng; Bertling, Karl; Ikonić, Zoran; Valavanis, Alexander; Dean, Paul; Cooper, Jonathan; Khanna, Suraj P; Lachab, Mohammad; Linfield, Edmund H; Davies, A Giles; Harrison, Paul; Indjin, Dragan; Rakić, Aleksandar D

    2016-09-01

    Optical feedback effects in lasers may be useful or problematic, depending on the type of application. When semiconductor lasers are operated using pulsed-mode excitation, their behavior under optical feedback depends on the electronic and thermal characteristics of the laser, as well as the nature of the external cavity. Predicting the behavior of a laser under both optical feedback and pulsed operation therefore requires a detailed model that includes laser-specific thermal and electronic characteristics. In this paper we introduce such a model for an exemplar bound-to-continuum terahertz frequency quantum cascade laser (QCL), illustrating its use in a selection of pulsed operation scenarios. Our results demonstrate significant interplay between electro-optical, thermal, and feedback phenomena, and that this interplay is key to understanding QCL behavior in pulsed applications. Further, our results suggest that for many types of QCL in interferometric applications, thermal modulation via low duty cycle pulsed operation would be an alternative to commonly used adiabatic modulation. PMID:27607659

  17. Polarizabilities of Impurity Doped Quantum Dots Under Pulsed Field: Role of Multiplicative White Noise

    NASA Astrophysics Data System (ADS)

    Saha, Surajit; Ghosh, Manas

    2016-02-01

    We perform a rigorous analysis of the profiles of a few diagonal and off-diagonal components of linear ( α xx , α yy , α xy , and α yx ), first nonlinear ( β xxx , β yyy , β xyy , and β yxx ), and second nonlinear ( γ xxxx , γ yyyy , γ xxyy , and γ yyxx ) polarizabilities of quantum dots exposed to an external pulsed field. Simultaneous presence of multiplicative white noise has also been taken into account. The quantum dot contains a dopant represented by a Gaussian potential. The number of pulse and the dopant location have been found to fabricate the said profiles through their interplay. Moreover, a variation in the noise strength also contributes evidently in designing the profiles of above polarizability components. In general, the off-diagonal components have been found to be somewhat more responsive to a variation of noise strength. However, we have found some exception to the above fact for the off-diagonal β yxx component. The study projects some pathways of achieving stable, enhanced, and often maximized output of linear and nonlinear polarizabilities of doped quantum dots driven by multiplicative noise.

  18. Electron motion induced by magnetic pulse in a bilayer quantum wire

    NASA Astrophysics Data System (ADS)

    Chwiej, T.

    2016-06-01

    We consider theoretical stimulation of electron motion in a quantum wire by means of ultrashort magnetic pulses of time duration between several and a few tens of picoseconds. In our considerations, an electron is confined in a nanowire which consists of two vertically stacked tunnel-coupled layers. If a magnetic pulse pierces this nanowire and its direction is parallel to the plane established by the layers, and additionally, it is perpendicular to the wire's axis, then the eigenstates of a single electron energy operator for vertical direction are hybridized by the off-diagonal terms of the full Hamiltonian. These terms depend linearly on the momentum operator, which means that such magnetically forced hybridization may induce electron motion in a nanowire. The classical counterpart of this quantum-mechanical picture is a situation in which the rotational electric field generated by a time-varying magnetic field pushes the charge densities localized in the upper and lower layers in opposite directions. We have found, however, that for an asymmetric vertical confinement in a bilayer nanowire, the major part of the single electron density starts to move in the direction of the local electric field in its layer forcing the minority part to move in this direction as well. It results in coherent motion of both densities in a particular direction. We analyze the dynamics of such motion in dependence on the time characteristics of a magnetic pulse and discuss potential applications of this effect in the construction of a magnetic valve.

  19. One-bit digital-to-analog converter based on rapid single flux quantum circuit

    NASA Astrophysics Data System (ADS)

    Hirayama, F.; Maezawa, M.; Suzuki, M.

    2007-10-01

    Rapid single flux quantum digital-to-analog (D/A) converters which synthesize arbitrary waveforms with metrological accuracy are under development. We propose a 1-bit RSFQ D/A converter which is expected to operate at higher sampling frequencies than the multi-bit converter and is suitable for multi-chip operation to achieve the output voltages exceeding 100 mV. Calculations of the noise power and the attenuation of the signal suggested that the rms error in a 10 kHz sine wave synthesized by the 1-bit converter with a third-order low-pass filter can be smaller than 10-7 at the sampling frequency of 100 MHz. A prototype 1-bit D/A converter was fabricated and the generation of dc voltages was confirmed as expected.

  20. 40-GHz operation of a single-flux-quantum (SFQ) 4 × 4 switch scheduler

    NASA Astrophysics Data System (ADS)

    Kameda, Y.; Yorozu, S.; Hashimoto, Y.; Terai, H.; Fujimaki, A.; Yoshikawa, N.

    2006-10-01

    We designed a single-flux-quantum (SFQ) scheduler for a 4 × 4 network switch. It receives requests serially and arbitrates them. Fair scheduling is achieved by using a round-robin priority pointer at each output port. The pointer is updated so that the input port that was granted permission has the lowest priority in the next scheduling cycle. We divided the scheduler into sub-blocks, which were separately designed. The sub-blocks, which have asynchronous interfaces, were then connected with passive transmission lines. Ladder-type on-chip clock generators were included in the circuit for high-speed operation. Using logic simulation, we verified the scheduler test circuit. The scheduler test circuit was composed of about 3000 Josephson junctions. We tested the scheduler circuit at high speed and confirmed correct operations at over 40 GHz.

  1. Implementation of energy efficient single flux quantum digital circuits with sub-aJ/bit operation

    NASA Astrophysics Data System (ADS)

    Volkmann, M. H.; Sahu, A.; Fourie, C. J.; Mukhanov, O. A.

    2013-01-01

    We report the first experimental demonstration of recently proposed energy efficient single flux quantum logic, eSFQ. This logic can represent the next generation of RSFQ logic, eliminating the dominant static power dissipation associated with a dc bias current distribution and providing over two orders of magnitude efficiency improvement over conventional RSFQ logic. We further demonstrate that the introduction of passive phase shifters allows the reduction of dynamic power dissipation by about 20%, reaching ˜0.8 aJ/bit operation. Two types of demonstration eSFQ circuit, shift registers and demultiplexers (deserializers), were implemented using the standard HYPRES 4.5 kA cm-2 fabrication process. In this paper, we present eSFQ circuit design and demonstrate the viability and performance metrics of eSFQ circuits through simulations and experimental testing.

  2. Quantum phase flip gate between distant nitrogen-vacancy-center ensembles coupled to superconducting flux qubits

    NASA Astrophysics Data System (ADS)

    Liu, A.-Peng; Cheng, Liu-Yong; Chen, Li; Su, Shi-Lei; Wang, Hong-Fu; Zhang, Shou

    2014-11-01

    We propose a scheme for realizing a quantum controlled phase flip (CPF) gate between two distant nitrogen-vacancy-center spin ensembles (NVEs). The two NVEs couple magnetically with two inductively coupled superconducting flux qubits (FQs). By using an additional energy level of the nitrogen-vacancy (NV) center, the CPF gate can be implemented within the null- and single-excitation subspaces and the external classical driven field is needless in our scheme. Because of the adoption of NVE instead of single NV center, the CPF operation can be greatly speeded up. Besides, we show that this gate provides us a source of cluster states generation on NVEs. Analyses on the influences of dissipation show that this gate is robust.

  3. Confinement and Lattice Quantum-Electrodynamic Electric Flux Tubes Simulated with Ultracold Atoms

    SciTech Connect

    Zohar, Erez; Reznik, Benni

    2011-12-30

    We propose a method for simulating (2+1)D compact lattice quantum-electrodynamics, using ultracold atoms in optical lattices. In our model local Bose-Einstein condensates' (BECs) phases correspond to the electromagnetic vector potential, and the local number operators represent the conjugate electric field. The well-known gauge-invariant Kogut-Susskind Hamiltonian is obtained as an effective low-energy theory. The field is then coupled to external static charges. We show that in the strong coupling limit this gives rise to ''electric flux tubes'' and to confinement. This can be observed by measuring the local density deviations of the BECs, and is expected to hold even, to some extent, outside the perturbative calculable regime.

  4. Quantum dot formation and dynamic scaling behavior of SnO2 nanocrystals induced by pulsed delivery

    NASA Astrophysics Data System (ADS)

    Chen, Z. W.; Lai, J. K. L.; Shek, C. H.

    2006-01-01

    Quantum dot formation and dynamic scaling behavior of SnO2 nanocrystals in coalescence regime for growth by pulsed-laser deposition is explored experimentally and theoretically, and the same is compared with that for continuous vapor deposition such as molecular-beam epitaxy. Using high-resolution transmission electron microscopy, unusual quantum dots of SnO2 nanocrystals are studied. We present kinetic Monte-Carlo simulations for pulsed-laser deposition in the submonolayer regime and give a description of the island distance versus pulse intensity. We found that the scaling exponent for pulsed-laser deposition is 1.28±0.03, which is significantly lower as compared to that for molecular-beam epitaxy (1.62±0.03). Theoretical simulations reveal that this attractive difference can be pursued to the large fraction of multiple droplet coalescence under pulsed vapor delivery.

  5. Coupled-channels quantum theory of electronic flux density in electronically adiabatic processes: fundamentals.

    PubMed

    Diestler, D J

    2012-03-22

    The Born-Oppenheimer (BO) description of electronically adiabatic molecular processes predicts a vanishing electronic flux density (j(e)), =1/2∫dR[Δ(b) (x;R) - Δ(a) (x;R)] even though the electrons certainly move in response to the movement of the nuclei. This article, the first of a pair, proposes a quantum-mechanical "coupled-channels" (CC) theory that allows the approximate extraction of j(e) from the electronically adiabatic BO wave function . The CC theory is detailed for H(2)(+), in which case j(e) can be resolved into components associated with two channels α (=a,b), each of which corresponds to the "collision" of an "internal" atom α (proton a or b plus electron) with the other nucleus β (proton b or a). The dynamical role of the electron, which accommodates itself instantaneously to the motion of the nuclei, is submerged in effective electronic probability (population) densities, Δ(α), associated with each channel (α). The Δ(α) densities are determined by the (time-independent) BO electronic energy eigenfunction, which depends parametrically on the configuration of the nuclei, the motion of which is governed by the usual BO nuclear Schrödinger equation. Intuitively appealing formal expressions for the electronic flux density are derived for H(2)(+). PMID:22103768

  6. Factors regulating soil surface CO2 and NOx flux in response to high temperature, pulse water events, and nutrient fertilization

    NASA Astrophysics Data System (ADS)

    Oikawa, P. Y.; Grantz, D. A.; Chatterjee, A.; Eberwein, J. R.; Allsman, L. A.; Jenerette, D.

    2012-12-01

    Trace gas emissions from the soil surface are often underestimated due to poor understanding of the factors regulating fluxes under extreme conditions when moisture can be highly variable. In particular, dynamics of soil surface trace gas emissions from hot agricultural regions can be difficult to predict due to the sporadic use of flood irrigation and nitrogen fertilization. Soil surface CO2 and NOx fluxes are especially difficult to predict due to nonlinear responses to pulse water and fertilization events. Additionally, models such as Lloyd and Taylor (1994) and Yienger and Levy II (1995) are not well parameterized for soil surface CO2 and NOx flux, respectively, under excessively high temperatures. We measured soil surface CO2 and NOx flux in an agricultural field transitioning from fallow to biofuel crop production (Sorghum bicolor). Soil surface CO2 flux was measured using CO2 probes coupled with the flux-gradient method. NOx measurements were made using chambers coupled with a NOx monitor. Our field site is located at the University of California Desert Research and Extension Center in the Imperial Valley of CA. Air temperatures regularly exceed 42°C in the summer. Flood irrigation is used at the site as well as nitrogen fertilizers. Soil respiration ranged from 0-15 μmoles CO2 m-2 s-1, with strong hysteresis observed both with and without plants. Soil CO2 fluxes measured in the fallow field before the biofuel crop was planted were temperature independent and mainly regulated by soil moisture. When plants were introduced, temperature became an important predictor for soil respiration as well as canopy height. NOx fluxes were highest at intermediate soil moisture and varied significantly across an irrigation cycle. NOx emissions were temperature dependent, ranging from 3-113 ng N cm-2 hr-1. Neither CO2 nor NOx emissions showed inhibition at soil temperatures up to 55°C. Models may underestimate fluxes of CO2 and NOx from hot agricultural regions due to

  7. Search for half-flux-quantum Little-Parks oscillations in mesoscopic rings of Sr2RuO4

    NASA Astrophysics Data System (ADS)

    Cai, Xinxin; Zakrzewski, Brian; Ying, Yiqun; Fobes, David; Liu, Tijiang; Mao, Zhiqiang; Liu, Ying

    2015-03-01

    Recent cantilever magnetometry measurements on micron-sized, doubly-connected crystals of Sr2RuO4 have indicated that a half-flux-quantum state may be present in this material. To provide independent evidence for the presence of this new topological object by electrical transport measurements and examine its stability, we carried out Little-Parks (L-P) oscillation measurements, which trace out the phase boundary of a system, on mesoscopic rings of Sr2RuO4. Sr2RuO4 rings were fabricated using a combination of mechanical exfoliation of Sr2RuO4 single crystals, photolithography, and focused ion beam techniques. Without an in-plane magnetic field, large-amplitude resistance oscillations of a full-flux quantum were found as ramping the out-of-plane field. When the in-plane field and the measurement current were sufficiently large, a pronounced second set of resistance peaks was observed in one sample, supporting the existence of half-flux-quantum states. Preparation and measurements on more samples have been carried out and the most recent measurements suggest that the half-flux-quantum states, if indeed present, are likely to be metastable. This work is supported by DOE under Grant DE-FG02-04ER46159.

  8. Pulsed laser deposition of Mn doped CdSe quantum dots for improved solar cell performance

    SciTech Connect

    Dai, Qilin; Wang, Wenyong E-mail: jtang2@uwyo.edu; Tang, Jinke E-mail: jtang2@uwyo.edu; Sabio, Erwin M.

    2014-05-05

    In this work, we demonstrate (1) a facile method to prepare Mn doped CdSe quantum dots (QDs) on Zn{sub 2}SnO{sub 4} photoanodes by pulsed laser deposition and (2) improved device performance of quantum dot sensitized solar cells of the Mn doped QDs (CdSe:Mn) compared to the undoped QDs (CdSe). The band diagram of photoanode Zn{sub 2}SnO{sub 4} and sensitizer CdSe:Mn QD is proposed based on the incident-photon-to-electron conversion efficiency (IPCE) data. Mn-modified band structure leads to absorption at longer wavelengths than the undoped CdSe QDs, which is due to the exchange splitting of the CdSe:Mn conduction band by the Mn dopant. Three-fold increase in the IPCE efficiency has also been observed for the Mn doped samples.

  9. Pulsed Excitation Dynamics of an Optomechanical Crystal Resonator near Its Quantum Ground State of Motion

    NASA Astrophysics Data System (ADS)

    Meenehan, Seán M.; Cohen, Justin D.; MacCabe, Gregory S.; Marsili, Francesco; Shaw, Matthew D.; Painter, Oskar

    2015-10-01

    Using pulsed optical excitation and read-out along with single-phonon-counting techniques, we measure the transient backaction, heating, and damping dynamics of a nanoscale silicon optomechanical crystal cavity mounted in a dilution refrigerator at a base temperature of Tf≈11 mK . In addition to observing a slow (approximately 740-ns) turn-on time for the optical-absorption-induced hot-phonon bath, we measure for the 5.6-GHz "breathing" acoustic mode of the cavity an initial phonon occupancy as low as ⟨n ⟩=0.021 ±0.007 (mode temperature Tmin≈70 mK ) and an intrinsic mechanical decay rate of γ0=328 ±14 Hz (Qm≈1.7 ×107). These measurements demonstrate the feasibility of using short pulsed measurements for a variety of quantum optomechanical applications despite the presence of steady-state optical heating.

  10. Efficient optical trapping of CdTe quantum dots by femtosecond laser pulses.

    PubMed

    Chiang, Wei-Yi; Okuhata, Tomoki; Usman, Anwar; Tamai, Naoto; Masuhara, Hiroshi

    2014-12-11

    The development in optical trapping and manipulation has been showing rapid progress, most of it is in the small particle sizes in nanometer scales, substituting the conventional continuous-wave lasers with high-repetition-rate ultrashort laser pulse train and nonlinear optical effects. Here, we evaluate two-photon absorption in optical trapping of 2.7 nm-sized CdTe quantum dots (QDs) with high-repetition-rate femtosecond pulse train by probing laser intensity dependence of both Rayleigh scattering image and the two-photon-induced luminescence spectrum of the optically trapped QDs. The Rayleigh scattering imaging indicates that the two-photon absorption (TPA) process enhances trapping ability of the QDs. Similarly, a nonlinear increase of the two-photon-induced luminescence with the incident laser intensity fairly indicates the existence of the TPA process. PMID:24926894

  11. Multiplexed Chirped Pulse Quantum Cascade Laser Measurements of Ammonia and Other Small Molecules

    NASA Astrophysics Data System (ADS)

    Picken, Craig; Langford, Nigel; Duxbury, Geoffrey

    2014-06-01

    Spectrometers based on Quantum Cascade (QC) lasers can be run in either continuous or pulsed operation. Although the instrumentation based upon the most recent versions of continuously operating QC lasers can have higher resolution than chirped lasers, using chirped pulse QC lasers can give an advantage when rapid changes in gas composition occur. For example, when jet engines are being tested, a variety of temperature dependent effects on the trace gas concentrations of the plume may be observed. Most pulsed QC lasers are operated in the down chirped mode, in which the chirp rate slows during the pulse. In our spectrometer the changes in frequency are recorded using two Ge etalons, one with a free spectral range of 0.0495 cm-1, and the other with a fringe spacing of 0.0195 cm-1.They can also be deployed in multiplex schemes in which two or more down-chirped lasers are used. In this paper we wish to show examples of the use of multiplexed chirped pulse lasers to allow overlapping spectra to be recorded. The examples of multiplex methods used are taken partly from measurements of 14NH3 and 15NH3 in the region from 1630 to 1622 cm-1, and partly from the use of other chirped pulse lasers operating in the 8 μm region. Among the effects seen are rapid passage effects caused by the rapid down-chirp, and the use of gases such as nitrogen to cause variation in the shape of the collisional broadened absorption lines.

  12. Pulsed-laser micropatterned quantum-dot array for white light source

    PubMed Central

    Wang, Sheng-Wen; Lin, Huang-Yu; Lin, Chien-Chung; Kao, Tsung Sheng; Chen, Kuo-Ju; Han, Hau-Vei; Li, Jie-Ru; Lee, Po-Tsung; Chen, Huang-Ming; Hong, Ming-Hui; Kuo, Hao-Chung

    2016-01-01

    In this study, a novel photoluminescent quantum dots device with laser-processed microscale patterns has been demonstrated to be used as a white light emitting source. The pulsed laser ablation technique was employed to directly fabricate microscale square holes with nano-ripple structures onto the sapphire substrate of a flip-chip blue light-emitting diode, confining sprayed quantum dots into well-defined areas and eliminating the coffee ring effect. The electroluminescence characterizations showed that the white light emission from the developed photoluminescent quantum-dot light-emitting diode exhibits stable emission at different driving currents. With a flexibility of controlling the quantum dots proportions in the patterned square holes, our developed white-light emitting source not only can be employed in the display applications with color triangle enlarged by 47% compared with the NTSC standard, but also provide the great potential in future lighting industry with the correlated color temperature continuously changed in a wide range. PMID:27005829

  13. A method towards simulating the total luminous flux of a monochromatic high power LED operated in a pulsed manner.

    PubMed

    Moolman, M C; Koek, W D; Urbach, H P

    2009-09-28

    High power light-emitting diodes (HPLEDs) are frequently being operated in a pulsed manner. The research presented here focuses on the optical, electrical and thermal behaviour of a HPLED under pulse width modulation (PWM), and has the following twofold aim. Firstly, investigating the temperature dependence of the HPLED's efficiency, where it was found that the exact method of operation and the definition of calculation is crucial when making claims. Secondly, we propose a method to simulate the absolute emitted luminous flux of a current driven HPLED under PWM. This is done by making use of experimentally determined characteristic parameters of the HPLED. This has as advantage that no further physical measurements are needed to investigate the HPLEDs behavior under numerous different PWM circumstances. PMID:19907530

  14. Hydrogen atom in a quantum plasma environment under the influence of Aharonov-Bohm flux and electric and magnetic fields.

    PubMed

    Falaye, Babatunde James; Sun, Guo-Hua; Silva-Ortigoza, Ramón; Dong, Shi-Hai

    2016-05-01

    This study presents the confinement influences of Aharonov-Bohm (AB) flux and electric and magnetic fields directed along the z axis and encircled by quantum plasmas on the hydrogen atom. The all-inclusive effects result in a strongly attractive system while the localizations of quantum levels change and the eigenvalues decrease. We find that the combined effect of the fields is stronger than a solitary effect and consequently there is a substantial shift in the bound state energy of the system. We also find that to perpetuate a low-energy medium for the hydrogen atom in quantum plasmas, a strong electric field and weak magnetic field are required, whereas the AB flux field can be used as a regulator. The application of the perturbation technique utilized in this paper is not restricted to plasma physics; it can also be applied in molecular physics. PMID:27300989

  15. Hydrogen atom in a quantum plasma environment under the influence of Aharonov-Bohm flux and electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Falaye, Babatunde James; Sun, Guo-Hua; Silva-Ortigoza, Ramón; Dong, Shi-Hai

    2016-05-01

    This study presents the confinement influences of Aharonov-Bohm (AB) flux and electric and magnetic fields directed along the z axis and encircled by quantum plasmas on the hydrogen atom. The all-inclusive effects result in a strongly attractive system while the localizations of quantum levels change and the eigenvalues decrease. We find that the combined effect of the fields is stronger than a solitary effect and consequently there is a substantial shift in the bound state energy of the system. We also find that to perpetuate a low-energy medium for the hydrogen atom in quantum plasmas, a strong electric field and weak magnetic field are required, whereas the AB flux field can be used as a regulator. The application of the perturbation technique utilized in this paper is not restricted to plasma physics; it can also be applied in molecular physics.

  16. Effect of a magnetic flux line on the quantum beats in the Henon-Heiles level density.

    PubMed

    Brack, M.; Bhaduri, R. K.; Law, J.; Maier, Ch.; Murthy, M. V. N.

    1995-03-01

    The quantum density of states of the Henon-Heiles potential displays a pronounced beating pattern. This has been explained by the interference of three isolated classical periodic orbits with nearby actions and periods. A singular magnetic flux line, passing through the origin, drastically alters the beats even though the classical Lagrangian equations of motion remain unchanged. Some of the changes can be easily understood in terms of the Aharonov-Bohm effect. However, we find that the standard periodic orbit theory does not reproduce the diffraction-like quantum effects on those classical orbits which intersect the singular flux line, and argue that corrections of relative order variant Planck's over 2pi are necessary to describe these effects. We also discuss the changes in the distribution of nearest-neighbor spacings in the eigenvalue spectrum, brought about by the flux line. (c) 1995 American Institute of Physics. PMID:12780185

  17. Two-photon interference of weak coherent laser pulses recalled from separate solid-state quantum memories

    NASA Astrophysics Data System (ADS)

    Jin, Jeongwan; Slater, Joshua A.; Saglamyurek, Erhan; Sinclair, Neil; George, Mathew; Ricken, Raimund; Oblak, Daniel; Sohler, Wolfgang; Tittel, Wolfgang

    2013-08-01

    Quantum memories allowing reversible transfer of quantum states between light and matter are central to quantum repeaters, quantum networks and linear optics quantum computing. Significant progress regarding the faithful transfer of quantum information has been reported in recent years. However, none of these demonstrations confirm that the re-emitted photons remain suitable for two-photon interference measurements, such as C-NOT gates and Bell-state measurements, which constitute another key ingredient for all aforementioned applications. Here, using pairs of laser pulses at the single-photon level, we demonstrate two-photon interference and Bell-state measurements after either none, one or both pulses have been reversibly mapped to separate thulium-doped lithium niobate waveguides. As the interference is always near the theoretical maximum, we conclude that our solid-state quantum memories, in addition to faithfully mapping quantum information, also preserve the entire photonic wavefunction. Hence, our memories are generally suitable for future applications of quantum information processing that require two-photon interference.

  18. Quantum phase amplification for temporal pulse shaping and super-resolution in remote sensing

    NASA Astrophysics Data System (ADS)

    Yin, Yanchun

    The use of nonlinear optical interactions to perform nonclassical transformations of electromagnetic field is an area of considerable interest. Quantum phase amplification (QPA) has been previously proposed as a method to perform nonclassical manipulation of coherent light, which can be experimentally realized by use of nonlinear optical mixing processes, of which phase-sensitive three-wave mixing (PSTWM) is one convenient choice. QPA occurs when PSTWM is operated in the photon number deamplification mode, i.e., when the energy is coherently transferred among the low-frequency signal and idler waves and the high-frequency pump wave. The final state is nonclassical, with the field amplitude squeezed and the phase anti-squeezed. In the temporal domain, the use of QPA has been studied to facilitate nonlinear pulse shaping. This novel method directly shapes the temporal electric field amplitude and phase using the PSTWM in a degenerate and collinear configuration, which has been analyzed using a numerical model. Several representative pulse shaping capabilities of this technique have been identified, which can augment the performance of common passive pulse shaping methods operating in the Fourier domain. The analysis indicates that a simple quadratic variation of temporal phase facilitates pulse compression and self-steepening, with features significantly shorter than the original transform-limited pulse. Thus, PSTWM can act as a direct pulse compressor based on the combined effects of phase amplification and group velocity mismatch, even without the subsequent linear phase compensation. Furthermore, it is shown numerically that pulse doublets and pulse trains can be produced at the pump frequency by utilizing the residual linear phase of the signal. Such pulse shaping capabilities are found to be within reach of this technique in common nonlinear optical crystals pumped by pulses available from compact femtosecond chirped-pulse amplification laser systems. The use of

  19. Effects of surface ligands and solvents on quantum dot photostability under pulsed UV laser irradiation

    NASA Astrophysics Data System (ADS)

    Krivenkov, Victor A.; Samokhvalov, Pavel S.; Linkov, Pavel A.; Prokhorov, Sergey D.; Martynov, Igor L.; Chistyakov, Alexander A.; Nabiev, Igor

    2015-05-01

    The organic ligands passivating the surface of semiconductor quantum dots (QDs) and the solvents used strongly determine the photostability of QD solutions. Highly purified QD solutions in chloroform have been shown to photodegrade upon pulsed ultraviolet (UV) irradiation, irrespectively of the type of surface ligand. However, the photostability of QDs dissolved in n-octane, a more photochemically inert solvent, strongly depends on the ligands passivating their surface. In n-octane, hexadecylamine-coated QDs are completely stable and display no photochemical response to pulsed UV laser irradiation. In solutions of octanethiol-capped QDs, the photoluminescence intensity slightly decreases under irradiation. QDs coated with trioctylphosphine oxide exhibit a more complex pattern of photobleaching, which depends on the initial value of fluorescence quantum yield of QDs. This complex pattern may be accounted for by two competing processes: (1) ligand photodesorption accompanied by photobleaching due to specific alignment of the band levels of QDs and highest occupied molecular orbital of the ligand and (2) photoinduced decrease in the population of trapping states. Furthermore, practically no thermodynamic degradation of QD solutions has been observed for the micromolar QD concentration used in the study, in contrast to lower concentrations, thus confirming the photoinduced origin of the changes caused by UV irradiation. Obtained results show that the photostability of QDs may be strongly increased by careful selection of the ligands passivating their surface and the solvents used in the experiments.

  20. A search for upstream pressure pulses associated with flux transfer events: An AMPTE/ISEE case study

    NASA Technical Reports Server (NTRS)

    Elphic, R. C.; Baumjohann, W.; Cattell, C. A.; Luehr, H.; Smith, M. F.

    1994-01-01

    On September 19, 1984, the Active Magnetospheric Particle Tracers Explorers (AMPTE) United Kingdom Satellite (UKS) and Ion Release Module (IRM) and International Sun Earth Explorers (ISEE) 1 and 2 spacecraft passed outbound through the dayside magnetopause at about the same time. The AMPTE spacecraft pair crossed first and were in the near-subsolar magnetosheath for more than an hour. Meanwhile the ISEE pair, about 5 R(sub E) to the south, observed flux transfer event (FTE) signatures. We use the AMPTE UKS and IRM plasma and field observations of magnetosheath conditions directly upstream of the subsolar magnetopause to check whether pressure pulses are responsible for the FTE signatures seen at ISEE. Pulses in both the ion thermal pressure and the dynamic pressure are observed in the magnetosheath early on when IRM and UKS are close to the magnetopause, but not later. These large pulses appear to be related to reconnection going on at the magnetopause nearby. AMPTE magnetosheath data far from the magnetopause do not show a pressure pulse correlation with FTEs at ISEE. Moreover, the magnetic pressure and tension effects seen in the ISEE FTEs are much larger than any pressure effects seen in the magnetosheath. A superposed epoch analysis based on small-amplitude peaks in the AMPTE magnetosheath total static pressure (nkT + B(exp 2)/2 mu(sub 0)) hint at some boundary effects, less than 5 nT peak-to-peak variations in the ISEE 1 and 2 B(sub N) signature starting about 1 min after the pressure peak epoch. However, these variations are much smaller than the standard deviations of the B(sub N) field component. Thus the evidence from this case study suggests that upstream magnetosheath pressure pulses do not give rise to FTEs, but may produce very small amplitude signatures in the magnetic field at the magnetopause.

  1. Pulse

    MedlinePlus

    Heart rate; Heart beat ... The pulse can be measured at areas where an artery passes close to the skin. These areas include the: ... side of the foot Wrist To measure the pulse at the wrist, place the index and middle ...

  2. Ultrafast single-electron transfer in coupled quantum dots driven by a few-cycle chirped pulse

    SciTech Connect

    Yang, Wen-Xing; Chen, Ai-Xi; Bai, Yanfeng; Lee, Ray-Kuang

    2014-04-14

    We theoretically study the ultrafast transfer of a single electron between the ground states of a coupled double quantum dot (QD) structure driven by a nonlinear chirped few-cycle laser pulse. A time-dependent Schrödinger equation without the rotating wave approximation is solved numerically. We demonstrate numerically the possibility to have a complete transfer of a single electron by choosing appropriate values of chirped rate parameters and the intensity of the pulse. Even in the presence of the spontaneous emission and dephasing processes of the QD system, high-efficiency coherent transfer of a single electron can be obtained in a wide range of the pulse parameters. Our results illustrate the potential to utilize few-cycle pulses for the excitation in coupled quantum dot systems through the nonlinear chirp parameter control, as well as a guidance in the design of experimental implementation.

  3. Energetic electron fluxes stimulated with pulsed injection of plasma in the ionosphere

    SciTech Connect

    Aleksandrov, V.A.; Babaev, A.P.; Gaidukov, V.Iu.; Loevskii, A.S.; Popov, G.A.; Romanovskii, Iu.A.

    1981-01-01

    Two plasma blob injection experiments, performed from the MR-12 rocket launched from Volgograd in 1977, are presented. The blobs were injected along and transverse to the magnetic field lines. An energetic electron flux increase was observed in both cases, the increase being 2-3 times greater than the background flux prior to injection in the longitudinal-injection experiment, and 10-40 times greater in the transverse-injection experiment. Plasma blob parameters presented include injection frequency, propulsive mass, and direction of the injection. Spectrum changes of the energetic electron pulsations were also observed.

  4. Flux amplification and sustainment of ST plasmas by multi-pulsed coaxial helicity injection on HIST

    NASA Astrophysics Data System (ADS)

    Higashi, T.; Ishihara, M.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

    2010-11-01

    The Helicity Injected Spherical Torus (HIST) device has been developed towards high-current start up and sustainment by Multi-pulsed Coaxial Helicity Injection (M-CHI) method. Multiple pulses operation of the coaxial plasma gun can build the magnetic field of STs and spheromak plasmas in a stepwise manner. So far, successive gun pulses on SSPX at LLNL were demonstrated to maintain the magnetic field of spheromak in a quasi-steady state against resistive decay [1]. The resistive 3D-MHD numerical simulation [2] for STs reproduced the current amplification by the M-CHI method and confirmed that stochastic magnetic field was reduced during the decay phase. By double pulsed operation on HIST, the plasma current was effectively amplified against the resistive decay. The life time increases up to 10 ms which is longer than that in the single CHI case (4 ms). The edge poloidal fields last between 0.5 ms and 6 ms like a repetitive manner. During the second driven phase, the toroidal ion flow is driven in the same direction as the plasma current as well as in the initial driven phase. At the meeting, we will discuss a current amplification mechanism based on the merging process with the plasmoid injected secondly from the gun. [1] B. Hudson et al., Phys. Plasmas Vol.15, 056112 (2008). [2] Y. Kagei et al., J. Plasma Fusion Res. Vol.79, 217 (2003).

  5. Manipulation of the nuclear spin ensemble in a quantum dot with chirped magnetic resonance pulses

    NASA Astrophysics Data System (ADS)

    Munsch, Mathieu; Wüst, Gunter; Kuhlmann, Andreas V.; Xue, Fei; Ludwig, Arne; Reuter, Dirk; Wieck, Andreas D.; Poggio, Martino; Warburton, Richard J.

    2014-09-01

    The nuclear spins in nanostructured semiconductors play a central role in quantum applications. The nuclear spins represent a useful resource for generating local magnetic fields but nuclear spin noise represents a major source of dephasing for spin qubits. Controlling the nuclear spins enhances the resource while suppressing the noise. NMR techniques are challenging: the group III and V isotopes have large spins with widely different gyromagnetic ratios; in strained material there are large atom-dependent quadrupole shifts; and nanoscale NMR is hard to detect. We report NMR on 100,000 nuclear spins of a quantum dot using chirped radiofrequency pulses. Following polarization, we demonstrate a reversal of the nuclear spin. We can flip the nuclear spin back and forth a hundred times. We demonstrate that chirped NMR is a powerful way of determining the chemical composition, the initial nuclear spin temperatures and quadrupole frequency distributions for all the main isotopes. The key observation is a plateau in the NMR signal as a function of sweep rate: we achieve inversion at the first quantum transition for all isotopes simultaneously. These experiments represent a generic technique for manipulating nanoscale inhomogeneous nuclear spin ensembles and open the way to probe the coherence of such mesoscopic systems.

  6. Efficient energy transfer in light-harvesting systems: Quantum-classical comparison, flux network, and robustness analysis

    NASA Astrophysics Data System (ADS)

    Wu, Jianlan; Liu, Fan; Ma, Jian; Silbey, Robert J.; Cao, Jianshu

    2012-11-01

    Following the calculation of optimal energy transfer in thermal environment in our first paper [J. L. Wu, F. Liu, Y. Shen, J. S. Cao, and R. J. Silbey, New J. Phys. 12, 105012 (2010), 10.1088/1367-2630/12/10/105012], full quantum dynamics and leading-order "classical" hopping kinetics are compared in the seven-site Fenna-Matthews-Olson (FMO) protein complex. The difference between these two dynamic descriptions is due to higher-order quantum corrections. Two thermal bath models, classical white noise (the Haken-Strobl-Reineker (HSR) model) and quantum Debye model, are considered. In the seven-site FMO model, we observe that higher-order corrections lead to negligible changes in the trapping time or in energy transfer efficiency around the optimal and physiological conditions (2% in the HSR model and 0.1% in the quantum Debye model for the initial site at BChl 1). However, using the concept of integrated flux, we can identify significant differences in branching probabilities of the energy transfer network between hopping kinetics and quantum dynamics (26% in the HSR model and 32% in the quantum Debye model for the initial site at BChl 1). This observation indicates that the quantum coherence can significantly change the distribution of energy transfer pathways in the flux network with the efficiency nearly the same. The quantum-classical comparison of the average trapping time with the removal of the bottleneck site, BChl 4, demonstrates the robustness of the efficient energy transfer by the mechanism of multi-site quantum coherence. To reconcile with the latest eight-site FMO model which is also investigated in the third paper [J. Moix, J. L. Wu, P. F. Huo, D. F. Coker, and J. S. Cao, J. Phys. Chem. Lett. 2, 3045 (2011), 10.1021/jz201259v], the quantum-classical comparison with the flux network analysis is summarized in Appendix C. The eight-site FMO model yields similar trapping time and network structure as the seven-site FMO model but leads to a more disperse

  7. Efficient energy transfer in light-harvesting systems: Quantum-classical comparison, flux network, and robustness analysis

    SciTech Connect

    Wu Jianlan; Liu Fan; Silbey, Robert J.; Cao Jianshu; Ma Jian

    2012-11-07

    Following the calculation of optimal energy transfer in thermal environment in our first paper [J. L. Wu, F. Liu, Y. Shen, J. S. Cao, and R. J. Silbey, New J. Phys. 12, 105012 (2010)], full quantum dynamics and leading-order 'classical' hopping kinetics are compared in the seven-site Fenna-Matthews-Olson (FMO) protein complex. The difference between these two dynamic descriptions is due to higher-order quantum corrections. Two thermal bath models, classical white noise (the Haken-Strobl-Reineker (HSR) model) and quantum Debye model, are considered. In the seven-site FMO model, we observe that higher-order corrections lead to negligible changes in the trapping time or in energy transfer efficiency around the optimal and physiological conditions (2% in the HSR model and 0.1% in the quantum Debye model for the initial site at BChl 1). However, using the concept of integrated flux, we can identify significant differences in branching probabilities of the energy transfer network between hopping kinetics and quantum dynamics (26% in the HSR model and 32% in the quantum Debye model for the initial site at BChl 1). This observation indicates that the quantum coherence can significantly change the distribution of energy transfer pathways in the flux network with the efficiency nearly the same. The quantum-classical comparison of the average trapping time with the removal of the bottleneck site, BChl 4, demonstrates the robustness of the efficient energy transfer by the mechanism of multi-site quantum coherence. To reconcile with the latest eight-site FMO model which is also investigated in the third paper [J. Moix, J. L. Wu, P. F. Huo, D. F. Coker, and J. S. Cao, J. Phys. Chem. Lett. 2, 3045 (2011)], the quantum-classical comparison with the flux network analysis is summarized in Appendix C. The eight-site FMO model yields similar trapping time and network structure as the seven-site FMO model but leads to a more disperse distribution of energy transfer pathways.

  8. Modification of quantum dots in Ge/Si nanostructures by pulsed laser irradiation

    SciTech Connect

    Volodin, V. A. Yakimov, A. I.; Dvurechenskii, A. V.; Efremov, M. D.; Nikiforov, A. I.; Gatskevich, E. I.; Ivlev, G. D.; Mikhalev, G. Yu.

    2006-02-15

    The goal of this study was the development of a method for the modification of a quantum dot (QD) structure in Ge/Si nanostructures by pulsed laser irradiation. The Ge{sub x}Si{sub 1-x} QD structures were analyzed using data furnished by Raman spectroscopy. Frequency-dependent admittance measurements were used to study the energy spectrum of holes in the Ge/Si heterostructures with Ge{sub x}Si{sub 1-x} QDs before and after the laser treatment. The obtained experimental data show that laser treatment makes it possible to reduce the sheet density of QDs, modify their composition, and increase the average size. The most important result is that the QD parameters become more uniform after the treatment with nanosecond laser pulses. In a sample with ODs of 8-nm average lateral size (six monolayers of Ge), the scatter of energy levels in the QD array is reduced by half after the treatment with 10 laser pulses.

  9. Exactly solvable two-state quantum model for a pulse of hyperbolic-tangent shape

    NASA Astrophysics Data System (ADS)

    Simeonov, Lachezar S.; Vitanov, Nikolay V.

    2014-04-01

    We present an analytically exactly solvable two-state quantum model, in which the coupling has a hyperbolic-tangent temporal shape and the frequency detuning is constant. The exact solution is expressed in terms of associated Legendre functions. An interesting feature of this model is that the excitation probability does not vanish, except for zero pulse area or zero detuning; this feature is attributed to the asymmetric pulse shape. Two limiting cases are considered. When the coupling rises very slowly, it is nearly linear and the tanh model reduces to the shark model introduced earlier. When the coupling rises very quickly, the tanh model reduces to the Rabi model, which assumes a rectangular pulse shape and hence a sudden switch on. Because of its practical significance, we have elaborated the asymptotics of the solution in the Rabi limit, and we have derived the next terms in the asymptotic expansion, which deliver the corrections to the amplitude and the phase of the Rabi oscillations due to the finite rise time of the coupling.

  10. A Burst and Simultaneous Short-term Pulsed Flux Enhancement fom the Magnetar Candidate 1E 1048.1-5937

    NASA Technical Reports Server (NTRS)

    Gavriil, Fotis P.; Kaspi, Victoria M.; Woods, Peter M.; Lyutikov, Maxim

    2005-01-01

    We report on the latest X-ray burst detected from the direction of the Anomalous X-ray Pulsar (AXP) 1E 1048.1-5937 using the Rossi X-ray Timing Explorer (RXTE). Following the burst the AXP was observed further with RXTE, XMM-Newton and Chandra. We find a simultaneous increase of approx. 3.7 times the quiescent value (approx. 5 sigma) in the pulsed component of the pulsar's flux during the tail of the burst which identifies the AXP as the burst's origin. The burst was overall very similar to the two others reported from this source in 2001. The unambiguous identification of 1E 1048.1-5937 as the burster here suggests it was in 2001 as well. Pre- and post-burst observations revealed no change in the total flux or spectrum of the quiescent emission. Comparing all three bursts detected thus far from this source we find that this event was the most fluent (170+/-42 x 10(exp -10) erg cm-2), had the highest peak flux (71+/-16 x 10(exp -10) erg/s/sq cm), the longest duration (approx. 411 s). The epoch of the burst peak was consistent with the arrival time of 1E 1048.1-5937's pulse peak. The burst exhibited significant spectral evolution with the trend going from hard to soft. Although the average spectrum of the burst was comparable in hardness (Gamma approx. 1) to those of the 2001 bursts, the peak of this burst was much harder (Gamma approx. 0.5).

  11. USING A HEAT PULSE TO MEASURE THE FLUX BETWEEN GROUNDWATER AND SURFACE WATER

    EPA Science Inventory

    EPA estimates that 10 percent of the sediments under the surface waters of the United States are contaminated and approximately 20 percent of the superfund sites include contaminated sediments. The risk associated with these contaminated sediments is directly related to the flux...

  12. Multi Function Heat Pulse Probes (MFHPP) to Estimate Ground Heat Flux and Reduce Surface Energy Budget Errors

    NASA Astrophysics Data System (ADS)

    Ciocca, Francesco; Sharma, Varun; Lunati, Ivan; Parlange, Marc B.

    2013-04-01

    Ground heat flux plays a crucial role in surface energy budget: an incorrect estimation of energy storage and heat fluxes in soils occur when probes such as heat flux plates are adopted, and these mistakes can account for up to 90% of the residual variance (Higgins, GRL, 2012). A promising alternative to heat flux plates is represented by Multi Function Heat Pulse Probes (MFHPP). They have proven to be accurate in thermal properties and heat fluxes estimation (e.g. Cobos, VZJ, 2003) and can be used to monitor and quantify subsurface evaporation in field experiments (Xiao et al., VZJ, 2011). We perform a laboratory experiment with controlled temperature in a small Plexiglas column (20cm diameter and 40cm height). The column is packed with homogeneously saturated sandy soil and equipped with three MFHPPs in the upper 4cm and thermocouples and dielectric soil moisture probes deeper. This configuration allows for accurate and simultaneous ground heat flux, soil moisture and subsurface evaporation measurements. Total evaporation is monitored using a precision scale, while an infrared gun and a long wave radiometer measure the soil skin temperature and the outgoing long-short wave radiation, respectively. A fan and a heat lamp placed above the column allow to mimick on a smaller and more controlled scale the field conditions induced by the diurnal cycle. At a reference height above the column relative humidity, wind speed and air temperature are collected. Results are interpreted by means of numerical simulations performed with an ad-hoc-developed numerical model that simulates coupled heat and moisture transfer in soils and is used to match and interpolate the temperature and soil moisture values got at finite depths within the column. Ground heat fluxes are then estimated by integrating over almost continuous, numerically simulated temperature profiles, which avoids errors due to use of discrete data (Lunati et al., WRR, 2012) and leads to a more reliable estimate of

  13. Automatic Single-Flux-Quantum (SFQ) Logic Synthesis Method for Top-Down Circuit Design

    NASA Astrophysics Data System (ADS)

    Kameda, Yoshio; Yorozu, Shinichi; Hashimoto, Yoshihito

    2006-06-01

    Single-flux-quantum (SFQ) logic circuits provide faster operations with lower power consumption, using Josephson junctions as the switching devices. In the top-down flow of SFQ circuit design, we have already developed a place-and-route tool that covers backend circuit design. In this paper, we present an automatic SFQ logic synthesis method that covers front-end circuit design. The logic synthesis is a process that generates a gate-level logic circuit from a functional specification written in hardware description languages. In our SFQ synthesis method, after we generate an intermediate circuit with the help of a synthesis tool for semiconductor circuits, we convert it into a gate-level pipelined SFQ circuit. To do this, an automatic synthesis tool was implemented. To evaluate the effectiveness of the method and the tool, we synthesized arithmetic and logic units (ALUs). It took only two and half minutes to synthesize a 64-bit-width ALU that consisted of about 18, 000 gates.

  14. Magnetic flux compression experiments on the Z pulsed-power accelerator

    NASA Astrophysics Data System (ADS)

    McBride, R. D.; Gomez, M. R.; Hansen, S. B.; Jennings, C. A.; Bliss, D. E.; Knapp, P. F.; Schmit, P. F.; Awe, T. J.; Martin, M. R.; Sinars, D. B.; Greenly, J. B.; Intrator, T. P.; Weber, T. E.

    2014-10-01

    We report on the progress made to date for diagnosing magnetic flux compression on Z. Each experiment consisted of an initially solid Be or Al liner (cylindrical tube), which was imploded using Z's drive current (0-20 MA in 100 ns). The imploding liner compresses a 10-T axial seed field, Bz(0), supplied by an independently driven Helmholtz coil pair. Assuming perfect flux conservation, the axial field amplification should be well described by Bz (t) =Bz (0) × [ R (0) / R (t) ]2 , where R is the liner's inner surface radius. With perfect flux conservation, Bz and dBz/dt values exceeding 104 T and 1012 T/s, respectively, are expected. These large values, the diminishing liner volume, and the harsh environment on Z, make it particularly challenging to measure these fields. We report our latest efforts to do so using three primary techniques: (1) micro B-dot probes, (2) streaked visible Zeeman spectroscopy, and (3) fiber-based Faraday rotation. We will also briefly highlight some recent developments using neutron diagnostics (ratio of secondary DT to primary DD neutrons and secondary DT neutron energy spectra) to assess the degree of magnetization in fully integrated magnetized liner inertial fusion (MagLIF) experiments on Z. This project was funded in part by Sandia's LDRD program and US DOE-NNSA Contract DE-AC04-94AL85000.

  15. A Burst and Simultaneous Short-Term Pulsed Flux Enhancement From The Magnetar Candidate 1E 1048.1-5937

    NASA Technical Reports Server (NTRS)

    Gavriil, Fotis P.; Kaspi, Victoria M.; Woods, Peter M.

    2006-01-01

    We report on the 2004 June 29 X-ray burst detected from the direction of the AXP 1E 1048.1-5937 using the RXTE. We find a simultaneous increase of approx. 3.5 times the quiescent value in the 2-10 keV pulsed flux of 1E 1048.1-5937 during the tail of the burst, which identifies the AXP as the burst s origin. The burst was overall very similar to the two others reported from the direction of this source in 2001. The unambiguous identification of 1E 1048.1-5937 as the burster here confirms that it was the origin of the 2001 bursts as well. The epoch of the burst peak was very close to the arrival time of 1E 1048.1-5937 s pulse peak. The burst exhibited significant spectral evolution, with the trend going from hard to soft. Although the average spectrum of the burst was comparable in hardness (Lambda approx. 1.6) to those,of the 2001 bursts, the peak of this burst was much harder (Lambda approx. 0.3). During the 11 days following the burst, the AXP was observed further with RXTE, XMM-Newton, and Chandra. Pre- and post-burst observations revealed no change in the total flux or spectrum of the quiescent emission. Comparing all three bursts detected thus far from this source, we find that this event was the most fluent (>3.3 x 10(exp-8 ergs/sq cm) in the 2-20 keV band), had the highest peak flux (59+/-9 x 10(exp -10)ergs/s/sq cm) in the 2-20 keV band), and had the longest duration (>699 s). The long duration of the burst difFerentiates it from SGR bursts, which have typical durations of approx.0.1 s. Bursts that occur preferentially at pulse maximum, have fast rises, and long X-tails containing the majority of the total burst energy have been seen uniquely from AXPs. The marked differences between AXP and SGRs bursts may provide new clues to help understand the physical differences between these objects.

  16. Gradient ascent pulse engineering approach to CNOT gates in donor electron spin quantum computing

    SciTech Connect

    Tsai, D.-B.; Goan, H.-S.

    2008-11-07

    In this paper, we demonstrate how gradient ascent pulse engineering (GRAPE) optimal control methods can be implemented on donor electron spin qubits in semiconductors with an architecture complementary to the original Kane's proposal. We focus on the high fidelity controlled-NOT (CNOT) gate and we explicitly find the digitized control sequences for a controlled-NOT gate by optimizing its fidelity using the effective, reduced donor electron spin Hamiltonian with external controls over the hyperfine A and exchange J interactions. We then simulate the CNOT-gate sequence with the full spin Hamiltonian and find that it has an error of 10{sup -6} that is below the error threshold of 10{sup -4} required for fault-tolerant quantum computation. Also the CNOT gate operation time of 100 ns is 3 times faster than 297 ns of the proposed global control scheme.

  17. Four-wave mixing in quantum wells using femtosecond pulses with Laguerre-Gauss modes

    NASA Astrophysics Data System (ADS)

    Persuy, Déborah; Ziegler, Marc; Crégut, Olivier; Kheng, Kuntheak; Gallart, Mathieu; Hönerlage, Bernd; Gilliot, Pierre

    2015-09-01

    We demonstrate theoretically and experimentally that four-wave mixing processes obey phase-matching conditions that determine not only the conservation of the photon energy and k-momentum but also the orbital angular momentum of light. We report on time-resolved four-wave mixing experiments performed on a CdTe/CdZnTe quantum well in both noncollinear and collinear configurations with Laguerre-Gauss beams. They demonstrate that the polarization wave which is induced in the material keeps memory of the excitation pulse orbital momentum. We show that in the collinear configuration, the large angular acceptance opens up new horizons for improving the spatial resolution in time-resolved experiments.

  18. Quantum speedup of uncoupled multiqubit open system via dynamical decoupling pulses

    NASA Astrophysics Data System (ADS)

    Song, Ya-Ju; Kuang, Le-Man; Tan, Qing-Shou

    2016-06-01

    We present a method to accelerate the dynamical evolution of mutltiqubit open system by employing dynamical decoupling pulses (DDPs) when the qubits are initially in W-type states. Here the qubits are independent and coupled to local Lorentzian reservoirs. It is found that this speedup evolution can be achieved in both the weak-coupling regime and the strong-coupling regime. The essential physical mechanism behind the acceleration evolution is explained as a result of the joint action of the non-Markovianity of reservoirs and the excited-state population of qubits. It is shown that both the non-Markovianity and the excited-state population can be controlled by DDPs to realize the quantum speedup.

  19. Origin of tunable photoluminescence from graphene quantum dots synthesized via pulsed laser ablation.

    PubMed

    Santiago, S R M; Lin, T N; Yuan, C T; Shen, J L; Huang, H Y; Lin, C A J

    2016-08-10

    A one-step synthesis of graphene quantum dots (GQDs) has been implemented using pulsed laser ablation (PLA) with carboxyl-functionalized multiwalled carbon nanotubes (MWCNTs). The synthesized GQDs with an average size smaller than 3 nm were obtained by the fragmentation of MWCNTs via oxidative cutting. The GQDs can generate tunable photoluminescence (PL) ranging from green to blue by controlling the PLA time. The PL spectrum (decay time) of the green GQDs remains unchanged under different excitation energies (emission energies), while that of the blue GQDs correlates with the excitation energy (emission energy). On the basis of the pH and temperature dependence of PL, we suggest that the localized intrinsic states associated with the sp(2) nanodomains and delocalized extrinsic states embedded on the GQD surface are responsible for blue and green emission in GQDs, respectively. PMID:27476476

  20. Composite-pulse magnetometry with a solid-state quantum sensor

    NASA Astrophysics Data System (ADS)

    Aiello, Clarice D.; Hirose, Masashi; Cappellaro, Paola

    2013-01-01

    The sensitivity of quantum magnetometer is challenged by control errors and, especially in the solid state, by their short coherence times. Refocusing techniques can overcome these limitations and improve the sensitivity to periodic fields, but they come at the cost of reduced bandwidth and cannot be applied to sense static or aperiodic fields. Here we experimentally demonstrate that continuous driving of the sensor spin by a composite pulse known as rotary-echo yields a flexible magnetometry scheme, mitigating both driving power imperfections and decoherence. A suitable choice of rotary-echo parameters compensates for different scenarios of noise strength and origin. The method can be applied to nanoscale sensing in variable environments or to realize noise spectroscopy. In a room-temperature implementation, based on a single electronic spin in diamond, composite-pulse magnetometry provides a tunable trade-off between sensitivities in the μTHz-1/2 range, comparable with those obtained with Ramsey spectroscopy, and coherence times approaching T1.

  1. High-quality quantum-dot-based full-color display technology by pulsed spray method

    NASA Astrophysics Data System (ADS)

    Chen, Kuo-Ju; Chen, Hsin-Chu; Tsai, Kai-An; Lin, Chien-Chung; Tsai, Hsin-Han; Chien, Shih-Hsuan; Cheng, Bo-Siao; Hsu, Yung-Jung; Shih, Min-Hsiung; Kuo, Hao-Chung

    2013-03-01

    We fabricated the colloidal quantum-dot light-emitting diodes (QDLEDs) with the HfO2/SiO2-distributed Bragg reflector (DBR) structure using a pulsed spray coating method. Moreover, pixelated RGB arrays, 2-in. wafer-scale white light emission, and an integrated small footprint white light device were demonstrated. The experimental results showed that the intensity of red, blue, and green (RGB) emissions exhibited considerable enhancement because of the high reflectivity in the UV region by the DBR structure, which subsequently increased the use in the UV optical pumping of RGB QDs. In this experiment, a pulsed spray coating method was crucial in providing uniform RGB layers, and the polydimethylsiloxane (PDMS) film was used as the interface layer between each RGB color to avoid crosscontamination and self-assembly of QDs. Furthermore, the chromaticity coordinates of QDLEDs with the DBR structure remained constant under various pumping powers in the large area sample, whereas a larger shift toward high color temperatures was observed in the integrated device. The resulting color gamut of the proposed QDLEDs covered an area 1.2 times larger than that of the NTSC standard, which is favorable for the next generation of high-quality display technology.

  2. VERITAS: a high-flux neutron reflectometer with vertical sample geometry for a long pulse spallation source

    NASA Astrophysics Data System (ADS)

    Mattauch, S.; Ioffe, A.; Lott, D.; Menelle, A.; Ott, F.; Medic, Z.

    2016-04-01

    An instrument concept of a reflectometer with a vertical sample geometry fitted to the long pulse structure of a spallation source, called “VERITAS” at the ESS, is presented. It focuses on designing a reflectometer with high intensity at the lowest possible background following the users' demand to investigate thin layers or interfacial areas in the sub-nanometer length scale. The high intensity approach of the vertical reflectometer fits very well to the long pulse structure of the ESS. Its main goal is to deliver as much usable intensity as possible at the sample position and be able to access a reflectivity range of 8 orders of magnitude and more. The concept assures that the reflectivity measurements can be performed in its best way to maximize the flux delivered to the sample. The reflectometer is optimized for studies of (magnetic) layers having thicknesses down to 5Å and a surface area of 1x1cm2. With reflectivity measurements the depth-resolved, laterally averaged chemical and magnetic profile can be investigated. By using polarised neutrons, additional vector information on the in-plane magnetic correlations (off-specular scattering at the pm length scale, GISANS at the nm length scale) can be studied. The full polarisation analysis could be used for soft matter samples to correct for incoherent scattering which is presently limiting neutron reflectivity studies to a reflectivity range on the order of 10-6.

  3. Structure Fragmentation in a Subsurface Nickel Titanium Layer Caused by its Irradiation with Pulsed Silicon ion Fluxes

    NASA Astrophysics Data System (ADS)

    Meisner, S. N.

    2014-07-01

    Using the methods of electron backscatter diffraction, an investigation of variations in microstructure of the subsurface nickel titanium layer after its irradiation with pulsed, medium-energy silicon ion fluxes is performed. It is shown that following this ion-beam irradiation of the specimen surfaces, the subsurface-layer structure changes and undergoes fragmentation down to as deep as 5-15 μm, which is smaller than the average grain size of the initial alloy. It is found out that the fragmented-structure layer is characterized by the presence of a martensitic В19' phase and a high concentration of interfaces and grain boundaries; the linear dimensions of the fragments exceed 1 μm, the structure refinement in the layer below the irradiated surface is nonuniform and depends on crystallographic orientation of the initial grain. A reason for intensive fragmentation of individual grains of the initial B2 phase after ion-beam treatment is assumed to be the proximity of the orientation axes of the principal slip planes to that of the incident ion beam flux. This might have resulted in an earlier, compared to other grains, onset of plastic deformation in these grains and, as a result, partial fragmentation of their structure.

  4. Long-term suppression of wetland methane flux following a pulse of simulated acid rain

    NASA Astrophysics Data System (ADS)

    Gauci, Vincent; Dise, Nancy; Blake, Stephen

    2005-06-01

    Wetlands are a potent source of the radiatively important gas methane (CH4). Recent findings have demonstrated that sulfate (SO42-) deposition via acid rain suppresses CH4 emissions by stimulating competitive exclusion of methanogens by sulfate-reducing microbial populations. Here we report data from a field experiment showing that a finite pulse of simulated acid rain SO42- deposition, as would be expected from a large Icelandic volcanic eruption, continues to suppress CH4 emissions from wetlands long after the pollution event has ceased. Our analysis of the stoichiometries suggests that 5 years is a minimum CH4 emission recovery period, with 10 years being a reasonable upper limit. Our findings highlight the long-term impact of acid rain on biospheric output of CH4 which, for discrete polluting events such as volcanic eruptions, outlives the relatively short-term SO42- aerosol radiative cooling effect.

  5. A Ku band pulsed electron paramagnetic resonance spectrometer using an arbitrary waveform generator for quantum control experiments at millikelvin temperatures.

    PubMed

    Yap, Yung Szen; Tabuchi, Yutaka; Negoro, Makoto; Kagawa, Akinori; Kitagawa, Masahiro

    2015-06-01

    We present a 17 GHz (Ku band) arbitrary waveform pulsed electron paramagnetic resonance spectrometer for experiments down to millikelvin temperatures. The spectrometer is located at room temperature, while the resonator is placed either in a room temperature magnet or inside a cryogen-free dilution refrigerator; the operating temperature range of the dilution unit is from ca. 10 mK to 8 K. This combination provides the opportunity to perform quantum control experiments on electron spins in the pure-state regime. At 0.6 T, spin echo experiments were carried out using γ-irradiated quartz glass from 1 K to 12.3 mK. With decreasing temperatures, we observed an increase in spin echo signal intensities due to increasing spin polarizations, in accordance with theoretical predictions. Through experimental data fitting, thermal spin polarization at 100 mK was estimated to be at least 99%, which was almost pure state. Next, to demonstrate the ability to create arbitrary waveform pulses, we generate a shaped pulse by superposing three Gaussian pulses of different frequencies. The resulting pulse was able to selectively and coherently excite three different spin packets simultaneously-a useful ability for analyzing multi-spin system and for controlling a multi-qubit quantum computer. By applying this pulse to the inhomogeneously broadened sample, we obtain three well-resolved excitations at 8 K, 1 K, and 14 mK. PMID:26133831

  6. A Ku band pulsed electron paramagnetic resonance spectrometer using an arbitrary waveform generator for quantum control experiments at millikelvin temperatures

    SciTech Connect

    Yap, Yung Szen; Tabuchi, Yutaka; Negoro, Makoto; Kagawa, Akinori; Kitagawa, Masahiro

    2015-06-15

    We present a 17 GHz (Ku band) arbitrary waveform pulsed electron paramagnetic resonance spectrometer for experiments down to millikelvin temperatures. The spectrometer is located at room temperature, while the resonator is placed either in a room temperature magnet or inside a cryogen-free dilution refrigerator; the operating temperature range of the dilution unit is from ca. 10 mK to 8 K. This combination provides the opportunity to perform quantum control experiments on electron spins in the pure-state regime. At 0.6 T, spin echo experiments were carried out using γ-irradiated quartz glass from 1 K to 12.3 mK. With decreasing temperatures, we observed an increase in spin echo signal intensities due to increasing spin polarizations, in accordance with theoretical predictions. Through experimental data fitting, thermal spin polarization at 100 mK was estimated to be at least 99%, which was almost pure state. Next, to demonstrate the ability to create arbitrary waveform pulses, we generate a shaped pulse by superposing three Gaussian pulses of different frequencies. The resulting pulse was able to selectively and coherently excite three different spin packets simultaneously—a useful ability for analyzing multi-spin system and for controlling a multi-qubit quantum computer. By applying this pulse to the inhomogeneously broadened sample, we obtain three well-resolved excitations at 8 K, 1 K, and 14 mK.

  7. A Ku band pulsed electron paramagnetic resonance spectrometer using an arbitrary waveform generator for quantum control experiments at millikelvin temperatures

    NASA Astrophysics Data System (ADS)

    Yap, Yung Szen; Tabuchi, Yutaka; Negoro, Makoto; Kagawa, Akinori; Kitagawa, Masahiro

    2015-06-01

    We present a 17 GHz (Ku band) arbitrary waveform pulsed electron paramagnetic resonance spectrometer for experiments down to millikelvin temperatures. The spectrometer is located at room temperature, while the resonator is placed either in a room temperature magnet or inside a cryogen-free dilution refrigerator; the operating temperature range of the dilution unit is from ca. 10 mK to 8 K. This combination provides the opportunity to perform quantum control experiments on electron spins in the pure-state regime. At 0.6 T, spin echo experiments were carried out using γ-irradiated quartz glass from 1 K to 12.3 mK. With decreasing temperatures, we observed an increase in spin echo signal intensities due to increasing spin polarizations, in accordance with theoretical predictions. Through experimental data fitting, thermal spin polarization at 100 mK was estimated to be at least 99%, which was almost pure state. Next, to demonstrate the ability to create arbitrary waveform pulses, we generate a shaped pulse by superposing three Gaussian pulses of different frequencies. The resulting pulse was able to selectively and coherently excite three different spin packets simultaneously—a useful ability for analyzing multi-spin system and for controlling a multi-qubit quantum computer. By applying this pulse to the inhomogeneously broadened sample, we obtain three well-resolved excitations at 8 K, 1 K, and 14 mK.

  8. Quantum beat oscillations in the two-color-photoionization continuum of neon and their dependence on the intensity of the ionizing laser pulse

    SciTech Connect

    Geiseler, Henning; Rottke, Horst; Steinmeyer, Guenter; Sandner, Wolfgang

    2011-09-15

    We investigate quantum beat oscillations in the photoionization continuum of Ne atoms that are photoionized by absorption of two photons via a group of excited bound states using ultrashort extreme ultraviolet and infrared laser pulses. The extreme ultraviolet pulse starts an excited-state wave packet that is photoionized by a high-intensity infrared pulse after a variable time delay. We analyze the continuum quantum beats from this two-step photoionization process and their dependence on the photoelectron kinetic energy. We find a pronounced dependence of the quantum beat amplitudes on the photoelectron kinetic energy. The dependence changes significantly with the applied infrared laser-pulse intensity. The experimental results are in good qualitative agreement with a model calculation that is adapted to the experimental situation. It accounts for the intensity dependence of the quantum beat structure through the coupling of the excited-state wave packet to other bound Ne states induced by the high-intensity infrared laser pulse.

  9. Pulse

    MedlinePlus

    ... resting for at least 10 minutes. Take the exercise heart rate while you are exercising. ... pulse rate can help determine if the patient's heart is pumping. ... rate gives information about your fitness level and health.

  10. Informatic analysis for hidden pulse attack exploiting spectral characteristics of optics in plug-and-play quantum key distribution system

    NASA Astrophysics Data System (ADS)

    Ko, Heasin; Lim, Kyongchun; Oh, Junsang; Rhee, June-Koo Kevin

    2016-07-01

    Quantum channel loopholes due to imperfect implementations of practical devices expose quantum key distribution (QKD) systems to potential eavesdropping attacks. Even though QKD systems are implemented with optical devices that are highly selective on spectral characteristics, information theory-based analysis about a pertinent attack strategy built with a reasonable framework exploiting it has never been clarified. This paper proposes a new type of trojan horse attack called hidden pulse attack that can be applied in a plug-and-play QKD system, using general and optimal attack strategies that can extract quantum information from phase-disturbed quantum states of eavesdropper's hidden pulses. It exploits spectral characteristics of a photodiode used in a plug-and-play QKD system in order to probe modulation states of photon qubits. We analyze the security performance of the decoy-state BB84 QKD system under the optimal hidden pulse attack model that shows enormous performance degradation in terms of both secret key rate and transmission distance.

  11. Pulse and noise properties of a two section passively mode-locked quantum dot laser under long delay feedback

    NASA Astrophysics Data System (ADS)

    Simos, Christos; Simos, Hercules; Mesaritakis, Charis; Kapsalis, Alexandros; Syvridis, Dimitris

    2014-02-01

    We present a numerical analysis that focuses on the temporal pulse properties of a monolithic two-section passively mode locked quantum dot laser subject to optical feedback from a very long external cavity. Pulse duration, shape and intensity noise are studied for the first time to our knowledge versus feedback delay and strength for the case of a passively mode locked semiconductor laser. These temporal characteristics are correlated to the previously observed dependence of repetition rate and timing jitter on cavity parameters in order to highlight the dynamics and complete the corresponding theoretical explanations.

  12. Quantum interference in laser-assisted photoionization and analytical methods for the measurement of an attosecond xuv pulse

    SciTech Connect

    Ge Yucheng; He Haiping

    2011-08-15

    Investigations of the quantum interference in laser-assisted photoionization by an attosecond extreme ultraviolet (xuv) pulse shows an approximately constant value for the total photoionizations for different laser intensities. The square of the full width at half maximum of a photoelectron energy spectrum (PES) linearly depends on the laser intensity. By determining the laser-related phase of each streaked electron and using a transfer equation with linear corrections, an analytically quick method is proposed for precisely reconstructing the xuv pulse intensity (chirp) from one (two) measured PES(s) with a theoretical root-mean-square temporal (energy) difference of less than 1 attosecond (0.1 eV).

  13. Quantum tricks with femtosecond light pulses teach magnetic devices to think ultrafast

    NASA Astrophysics Data System (ADS)

    Perakis, I. E.; Lingos, P. C.; Wang, J.

    2014-03-01

    The technological demand to push the gigahertz switching speed limit of today's magnetic memory/logic devices into the terahertz (1THz=1ps-1) regime underlies the entire field of spin-electronics and integrated multi- functional devices. This challenge is met by all-optical magnetic switching based on coherent spin manipulation By analogy to femto-chemistry and photosynthetic dynamics where photo-products of chemical/biochemical re- actions can be influenced by creating suitable superpositions of molecular states, femtosecond (fs) laser-excited coherence between spin/orbital/charge states can switch magnetic orders, by "suddenly" breaking the delicate balance between competing phases of correlated materials, e.g., the colossal magneto-resistive (CMR) manganites suitable for applications. Here we discuss femtosecond (fs) all-optical switching from antiferro- to ferromagnetic ordering via establishment of a magnetization increase within ˜100 fs, while the laser field still interacts with the system. Such non-equilibrium ferromagnetic correlations arise from quantum spin-flip fluctuations corre- lated with coherent superpositions of electronic states. The development of ferromagnetic correlations during the fs laser pulse reveals an initial quantum coherent regime of magnetism, clearly distinguished from the pi- cosecond lattice-heating regime characterized by phase separation. We summarize a microscopic theory based on density matrix equations of motion for composite fermion Hubbard operators, instead of bare electrons, that take into account the strong spin and charge local correlations. Our work merges two fields, femto-magnetism in metals/band insulators and non-equilibrium phase transitions of strongly correlated electrons, where local interactions exceeding the kinetic energy produce a complex balance of competing orders.

  14. Inverse method for simultaneous determination of soil water flux density and thermal properties with a penta-needle heat pulse probe

    NASA Astrophysics Data System (ADS)

    Yang, Changbing; Sakai, Masaru; Jones, Scott B.

    2013-09-01

    An accurate method for determination of in situ soil water flux density continues to be the most sought after and yet elusive hydrologic measurement. The penta-needle heat pulse probe (PHPP) employs a central heater needle surrounded by an orthogonal arrangement of four thermistor needles for two-component water flux density estimation. An analytical solution and inverse fitting method are presented for simultaneous estimation of thermal properties and soil water flux density using PHPP measurements. The approach yields estimates of both components of the flux in a plane normal to the axis of the PHPP needles. The method was evaluated using data measured by PHPPs in a laboratory experiment using a wide range of saturated water fluxes ranging from 1.2 to 33,200 cm d-1. Improved water flux density determination was achieved from zero-flux adjusted estimates of the apparent heater-thermistor radii, radj, which were used in the inverse analysis. Thermal diffusivity and conductivity were estimated with coefficients of variation less than 1.35%, indicating that the inverse problem is well posed and yields unique parameter estimates when water flux is less than 2000 cm d-1. Estimates of the x and y components of water flux density agreed well with measured water fluxes up to 7000 cm d-1 exhibiting R2 values greater than 0.976. Estimation of water flow direction based on 2-D water flux density was in good agreement with installation angle for water fluxes ranging from 10 to 7000 cm d-1.

  15. Niobium nitride-based analog to digital converter using rapid single flux quantum logic operating at 9.5 K

    NASA Astrophysics Data System (ADS)

    Radparvar, Masoud; Rylov, Sergey

    1994-06-01

    An analog to digital converter (ADC) using the rapid single flux quantum (RSFQ) logic family implemented in niobium nitride (NbN) technology is described. The circuit was originally developed and demonstrated in niobium technology. An identical circuit was then laid out, fabricated and demonstrated in NbN technology. The chips were fabricated using an eight-layer NbN-based process with Josephson junction critical current density of 500 A/sq cm. In this paper, we report on the measurement results for a 6-bit flux quantizing ADC which exhibited proper operation and good dc bias margins. We will also demonstrate results from an ADC chip operating up to 9.5 K.

  16. Controlling the magnetic susceptibility in an artificial elliptical quantum ring by magnetic flux and external Rashba effect

    SciTech Connect

    Omidi, Mahboubeh Faizabadi, Edris

    2015-03-21

    Magnetic susceptibility is investigated in a man-made elliptical quantum ring in the presence of Rashba spin-orbit interactions and the magnetic flux. It is shown that magnetic susceptibility as a function of magnetic flux changes between negative and positive signs periodically. The periodicity of the Aharonov-Bohm oscillations depends on the geometry of the region where magnetic field is applied, the eccentricity, and number of sites in each chain ring (the elliptical ring is composed of chain rings). The magnetic susceptibility sign can be reversed by tuning the Rashba spin-orbit strength as well. Both the magnetic susceptibility strength and sign can be controlled via external spin-orbit interactions, which can be exploited in spintronics and nanoelectronics.

  17. Statistical-fluctuation analysis for quantum key distribution with consideration of after-pulse contributions

    NASA Astrophysics Data System (ADS)

    Li, Hongxin; Jiang, Haodong; Gao, Ming; Ma, Zhi; Ma, Chuangui; Wang, Wei

    2015-12-01

    The statistical fluctuation problem is a critical factor in all quantum key distribution (QKD) protocols under finite-key conditions. The current statistical fluctuation analysis is mainly based on independent random samples, however, the precondition cannot always be satisfied because of different choices of samples and actual parameters. As a result, proper statistical fluctuation methods are required to solve this problem. Taking the after-pulse contributions into consideration, this paper gives the expression for the secure key rate and the mathematical model for statistical fluctuations, focusing on a decoy-state QKD protocol [Z.-C. Wei et al., Sci. Rep. 3, 2453 (2013), 10.1038/srep02453] with a biased basis choice. On this basis, a classified analysis of statistical fluctuation is represented according to the mutual relationship between random samples. First, for independent identical relations, a deviation comparison is made between the law of large numbers and standard error analysis. Second, a sufficient condition is given that the Chernoff bound achieves a better result than Hoeffding's inequality based on only independent relations. Third, by constructing the proper martingale, a stringent way is proposed to deal issues based on dependent random samples through making use of Azuma's inequality. In numerical optimization, the impact on the secure key rate, the comparison of secure key rates, and the respective deviations under various kinds of statistical fluctuation analyses are depicted.

  18. Ultra-broadband Superradiant Pulses from Femtosecond Laser Pumped InP based Quantum Well Laser Diode

    NASA Astrophysics Data System (ADS)

    Liu, Jingjing

    Laser techniques, such as gain / Q switching, mode-locking, have successfully overcome the energy restriction of gain clamping in the stead-state operated lasers, and allowed the generation of giant pulses with short pulse durations. However, gain saturation further limits the amount of stored energy in a gain medium, and therefore limits the possible maximum pulse energy obtained by laser techniques. Here we circumvent both gain clamping and the capacity limitation of energy storage by operating the double-quantum-well laser diode chips on ultrafast gain-switching model using femtosecond (fs) laser pulses as the optical pump. The advantage of our pumping approach is that the fs pulse can instantly produce a very large number of carriers, and therefore enable the formation of non-equilibrium coherent e-h BCS-like condensate state in a large energy region from the lowest QW subband edges to the highest subband and then obtain the ultra-broadband superradiant pulses. Superradiance (SR) or the coherent spontaneous emission is not a new quantum optics phenomenon, which has been proposed in 1954 by R. Dicke, even earlier than the invention of laser. It is famous as by its ultrashort duration, high peak power, high coherence and high timing jitter. Recently, femtosecond SR pulses have been generated from semiconductors. This investigation has revived both theoretical and experimental studies of SR emission. In this thesis, we have demonstrated the generation of intense, delayed SR pulses from the InP based double quantum well laser diode at room temperature. The 1040 nm femtosecond laser was applied as the optical pumping source, and when the pump power is high enough, the cooperative recombination of e-h pairs from higher order quantum energy levels can occur to generate SR bursts earlier than the cooperative emission from the lower quantum energy levels. Then, ultra-broadband TM polarized SR pulses have been firstly generated at room temperature. Our experiments also

  19. Quantum path control and isolated attosecond pulse generation in the combination of near-infrared and terahertz pulses

    NASA Astrophysics Data System (ADS)

    Zhong, Hui-Ying; Guo, Jing; Zhang, Hong-Dan; Du, Hui; Liu, Xue-Shen

    2015-07-01

    We present an efficient and realizable scheme for the generation of an ultrashort single attosecond (as) pulse from H atom with a 800-nm fundamental laser field combined with a terahertz (THz) field. The high-order harmonic generation (HHG) can be obtained by solving the time-dependent Schrödinger equation accurately and efficiently with time-dependent generalized pseudo-spectral (TDGPS) method. The result shows that the plateau of high-order harmonics is extended and the broadband spectra can be produced by the combined laser pulse, which can be explained by the corresponding ionization probability. The time-frequency analysis and semi-classical three-step model are also presented to further investigate this mechanism. Besides, by the superposition of the harmonics near the cutoff region, an isolated 133-as pulse can be obtained. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174108, 11104108, and 11271158).

  20. Nitrous Oxide Emission Flux Measurements for Ecological Systems with an Open-Path Quantum Cascade Laser-Based Sensor

    NASA Astrophysics Data System (ADS)

    Tao, L.; Sun, K.; Cavigelli, M. A.; Gelfand, I.; Zenone, T.; Cui, M.; Miller, D. J.; Khan, M. A.; Zondlo, M. A.

    2012-12-01

    The ambient concentration of nitrous oxide (N2O), the fourth most abundant greenhouse gas, is rapidly increasing with emissions from both natural and anthropogenic sources [1]. Soil and aquatic areas are important sources and sinks for N2O due to complicated biogenic processes. However, N2O emissions are poorly constrained in space and time, despite its importance to global climate change and ozone depletion. We report our recent N2O emission measurements with an open-path quantum cascade laser (QCL)-based sensor for ecological systems. The newly emergent QCLs have been used to build compact, sensitive trace gas sensors in the mid-IR spectral region. A compact open-path QCL based sensor was developed to detect atmospheric N2O and CO at ~ 4.5 μm using wavelength modulation spectroscopy (WMS) to achieve a sensitivity of 0.26 ppbv of N2O and 0.24 ppbv of CO in 1 s with a power consumption of ~50 W [2]. This portable sensor system has been used to perform N2O emission flux measurement both with a static flux chamber and on an eddy covariance (EC) flux tower. In the flux chamber measurements, custom chambers were used to host the laser sensor, while gas samples for gas chromatograph (GC) were collected at the same time in the same chamber for validation and comparison. Different soil treatments have been applied in different chambers to study the relationship between N2O emission and the amount of fertilizer (and water) addition. Measurements from two methods agreed with each other (95% or higher confidence interval) for emission flux results, while laser sensor gave measurements with a much high temporal resolution. We have also performed the first open-path eddy covariance N2O flux measurement at Kellogg research station, Michigan State University for a month in June, 2012. Our sensor was placed on a 4-meter tower in a corn field and powered by batteries (connected with solar panels). We have observed the diurnal cycle of N2O flux. During this deployment, an inter

  1. Second-order shaped pulsed for solid-state quantum computation

    SciTech Connect

    Sengupta, Pinaki

    2008-01-01

    We present the construction and detailed analysis of highly optimized self-refocusing pulse shapes for several rotation angles. We characterize the constructed pulses by the coefficients appearing in the Magnus expansion up to second order. This allows a semianalytical analysis of the performance of the constructed shapes in sequences and composite pulses by computing the corresponding leading-order error operators. Higher orders can be analyzed with the numerical technique suggested by us previously. We illustrate the technique by analyzing several composite pulses designed to protect against pulse amplitude errors, and on decoupling sequences for potentially long chains of qubits with on-site and nearest-neighbor couplings.

  2. Quantum dynamics of a two-state system induced by a chirped zero-area pulse

    NASA Astrophysics Data System (ADS)

    Lee, Han-gyeol; Song, Yunheung; Kim, Hyosub; Jo, Hanlae; Ahn, Jaewook

    2016-02-01

    It is well known that area pulses make Rabi oscillation and chirped pulses in the adiabatic interaction regime induce complete population inversion of a two-state system. Here we show that chirped zero-area pulses could engineer an interplay between the adiabatic evolution and Rabi-like rotations. In a proof-of-principle experiment utilizing spectral chirping of femtosecond laser pulses with a resonant spectral hole, we demonstrate that the chirped zero-area pulses could induce, for example, complete population inversion and return of the cold rubidium atom two-state system. Experimental result agrees well with the theoretically considered overall dynamics, which could be approximately modeled to a Ramsey-like three-pulse interaction, where the x and z rotations are driven by the hole and the main pulse, respectively.

  3. University of Illinois nuclear pumped laser program. [experiments with a TRIGA pulsed reactor with a broad pulse and a low peak flux

    NASA Technical Reports Server (NTRS)

    Miley, G. H.

    1979-01-01

    The development of nuclear pumped lasers with improved efficiency, energy storage capability, and UF6 volume pumping is reviewed. Results of nuclear pumped laser experiments using a TRIGA-type pulsed reactor are outlined.

  4. 10  GHz pulse repetition rate Er:Yb:glass laser modelocked with quantum dot semiconductor saturable absorber mirror.

    PubMed

    Resan, B; Kurmulis, S; Zhang, Z Y; Oehler, A E H; Markovic, V; Mangold, M; Südmeyer, T; Keller, U; Hogg, R A; Weingarten, K J

    2016-05-10

    Semiconductor saturable absorber mirror (SESAM) modelocked high pulse repetition rate (≥10  GHz) diode-pumped solid-state lasers are proven as an enabling technology for high data rate coherent communication systems owing to their low noise and high pulse-to-pulse optical phase-coherence. Compared to quantum well, quantum dot (QD)-based SESAMs offer potential advantages to such laser systems in terms of reduced saturation fluence, broader bandwidth, and wavelength flexibility. Here, we describe the first 10 GHz pulse repetition rate QD-SESAM modelocked laser at 1.55 μm, exhibiting 2 ps pulse width from an Er-doped glass oscillator (ERGO). The 10 GHz ERGO laser is modelocked with InAs/GaAs QD-SESAM with saturation fluence as low as 9  μJ/cm2. PMID:27168291

  5. Novel design of rapid single flux quantum logic based on a single layer of a high-Tc superconductor

    NASA Astrophysics Data System (ADS)

    Kaplunenko, V. K.; Ivanov, Z. G.; Stepantsov, E. A.; Claeson, T.; Holst, T.; Sun, Z. J.; Kromann, R.; Shen, Y. Q.; Vase, P.; Freltoft, T.; Wikborg, E.

    1995-07-01

    We suggest a new design of rapid single flux quantum (RSFQ) logic circuits which is based on a single superconducting layer and does not require a superconducting ground plane. Small inductances of about 10 pH, obligatory for RSFQ circuits, are formed as narrow slits of widths comparable to the London penetration depth (≂0.15 μm). The design allows us to decrease the geometric size of the RSFQ cell. Test circuits with YBaCuO grain boundary junctions on asymmetric 32° Y- ZrO2 bicrystals were used to measure the slit inductance per unit length and the mutual inductance of neighboring slits. A typical inductance of a 0.4 μm slit was found to be 0.7-0.8 pH/μm.

  6. A rapid single flux quantum 1 bit arithmetic logic unit constructed with a half-adder cell

    NASA Astrophysics Data System (ADS)

    Jung, K. R.; Kim, J. Y.; Kang, J. H.; Kirichenko, A. F.; Park, J. H.; Hahn, T. S.

    2004-06-01

    We have designed, fabricated, and tested a rapid single flux quantum (RSFQ) 1 bit arithmetic logic unit (ALU) block. The circuit consists of three DC current driven SFQ switches and a half-adder. We successfully tested the half-adder cell at clock frequency up to 20 GHz. The switches were commutating output ports of the half-adder to produce AND, OR, XOR, or ADD functions. For a high-speed test, we attached two switches at the input ports of the half-adder to control the high-speed input data by low-frequency pattern generators. The output in this measurement was an eye-diagram. Using this set-up, the circuit was successfully tested up to 20 GHz. The chip was fabricated using a standard HYPRES 1 kA cm-2 Nb Josephson junction fabrication process.

  7. A scheme for two-photon lasing with two coupled flux qubits in circuit quantum electrodynamics

    NASA Astrophysics Data System (ADS)

    Huang, Wen; Zou, Xu-Bo; Guo, Guang-Can

    2015-06-01

    We theoretically study the system of a superconducting transmission line resonator coupled to two interacting superconducting flux qubits. It is shown that under certain conditions the resonator mode can be tuned to two-photon resonance between the ground state and the highest excited state while the middle excited states are far-off resonance. Furthermore, we study the steady-state properties of the flux qubits and resonator, such as the photon statistics, the spectrum and squeezing of the resonator, and demonstrate that two-photon laser can be implemented with current experimental technology. Project supported by the National Fundamental Research Program of China (Grant No. 2011cba00200), the National Natural Science Foundation of China (Grant No. 11274295), and the Doctor Foundation of Education Ministry of China (Grant No. 20113402110059).

  8. Quantum Path Selection and Isolated-Attosecond-Pulse Generation of H2+ with an Intense Laser Pulse and a Static Field

    NASA Astrophysics Data System (ADS)

    Miao, Xiang-Yang; Liu, Sha-Sha

    2015-01-01

    We theoretically investigate the high-order-harmonic generation from the H2+ molecular ion exposed to the combination of an intense trapezoidal laser and a static field. The results show that the harmonic spectrum is obviously extended and the short quantum path is selected to contribute to the spectrum, because the corresponding long path is seriously suppressed. Then the combined Coulomb and laser field potentials and the time-dependent electron wave packet distributions are applied to illustrate the physical mechanism of high-order harmonic generation. Finally, by adjusting the intensity of the static field and superposing a properly selected range of the HHG spectrum, a 90-as isolated attosecond pulse is straightforwardly obtained.

  9. Nondestructive Encapsulation of CdSe/CdS Quantum Dots in an Inorganic Matrix by Pulsed Laser Deposition.

    PubMed

    Aubret, Antoine; Houel, Julien; Pereira, Antonio; Baronnier, Justine; Lhuillier, Emmanuel; Dubertret, Benoit; Dujardin, Christophe; Kulzer, Florian; Pillonnet, Anne

    2016-08-31

    We report the successful encapsulation of colloidal quantum dots in an inorganic matrix by pulsed laser deposition. Our technique is nondestructive and thus permits the incorporation of CdSe/CdS core/shell colloidal quantum dots in an amorphous yttrium oxide matrix (Y2O3) under full preservation of the advantageous optical properties of the nanocrystals. We find that controlling the kinetic energy of the matrix precursors by means of the oxygen pressure in the deposition chamber facilitates the survival of the encapsulated species, whose well-conserved optical properties such as emission intensity, luminescence spectrum, fluorescence lifetime, and efficiency as single-photon emitters we document in detail. Our method can be extended to different types of nanoemitters (e.g., nanorods, dots-in-rods, nanoplatelets) as well as to other matrices (oxides, semiconductors, metals), opening up new vistas for the realization of fully inorganic multilayered active devices based on colloidal nano-objects. PMID:27503143

  10. Highly doped p-ZnTe films and quantum well structures grown by nonequilibrium pulsed laser ablation

    SciTech Connect

    Lowndes, D.H.; Rouleau, C.M.; Budai, J.D.; Geohegan, D.B.; McCamy, J.W.

    1995-06-01

    Highly p-doped ZnTe films have been grown on semi-insulating GaAs (001) and unintentionally doped (p-type) GaSb (001) substrates by pulsed KrF (248 nm) excimer laser ablation of a ZnTe target through an N{sub 2} ambient, without the use of any assisting (DC or AC) plasma source. Free hole concentrations in the mid-10{sup 19} cm{sup {minus}3} to > 10{sup 20} cm{sup {minus}3} range have been obtained. This appears to be the first time that any wide band gap (E{sub g} {ge} 2 eV) II-VI compound (or other) semiconductor has been impurity-doped from the gas phase by pulsed-laser ablation (PLA). The maximum carrier concentrations also may be the highest obtained for ZnTe by any method thus far. Because pulsed laser deposition is inherently digital, attractive deposition rates can be combined with precise control of layer thickness in epitaxial multilayered structures. Typical deposition conditions are < 0.5 {angstrom} per laser pulse, with crystalline quality governed by tradeoffs between substrate temperature, pulse repetition rate, and the focused pulsed laser energy density. PLA`s capability for growth of very thin epitaxial layers is being exploited and studied through growth of doped heteroepitaxial quantum well structures in the nearly lattice-matched ZnTe/CdSe//GaSb(substrate) system. Results obtained from growth and characterization of heterostructures in this system will be presented.

  11. Spectral modification of the laser emission of a terahertz quantum cascade laser induced by broad-band double pulse injection seeding

    SciTech Connect

    Markmann, Sergej Nong, Hanond Hekmat, Negar; Jukam, Nathan; Pal, Shovon; Scholz, Sven; Kukharchyk, Nadezhda; Ludwig, Arne; Wieck, Andreas D.; Dhillon, Sukhdeep; Tignon, Jérôme; Marcadet, Xavier; Bock, Claudia; Kunze, Ulrich

    2015-09-14

    We demonstrate by injection seeding that the spectral emission of a terahertz (THz) quantum cascade laser (QCL) can be modified with broad-band THz pulses whose bandwidths are greater than the QCL bandwidth. Two broad-band THz pulses delayed in time imprint a modulation on the single THz pulse spectrum. The resulting spectrum is used to injection seed the THz QCL. By varying the time delay between the THz pulses, the amplitude distribution of the QCL longitudinal modes is modified. By applying this approach, the QCL emission is reversibly switched from multi-mode to single mode emission.

  12. Formation of ultrashort pulses via quantum interference between Stark-split atomic transitions in a hydrogenlike medium

    NASA Astrophysics Data System (ADS)

    Antonov, V. A.; Radeonychev, Y. V.; Kocharovskaya, Olga

    2013-11-01

    We derive the analytical solution uncovering the origin of the ultrashort pulse formation from the resonant radiation in a hydrogenlike medium [Y. V. Radeonychev, V. A. Polovinkin, and O. Kocharovskaya, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.183902 105, 183902 (2010)], which is a quantum interference of the atomic transitions from the ground to the first excited energy level split by an intense far-off-resonant laser field due to the instantaneous Stark effect into the periodically oscillating sublevels and interference of the resonantly scattered radiation with the incident one. The analytical solution shows that the pulses are almost bandwidth limited and can be produced in a wide range of parameters in excellent agreement with the more general numerical simulation. The experimental schemes to form few-femtosecond pulses from 122-nm radiation in atomic hydrogen as well as few-hundred-attosecond pulses from 13.74-nm radiation in a Li2+ medium are discussed.

  13. High-Speed Operation of a Single-Flux-Quantum (SFQ) Cross/Bar Switch up to 35 GHz

    NASA Astrophysics Data System (ADS)

    Kameda, Yoshio; Yorozu, Shinichi; Terai, Hirotaka; Fujimaki, Akira

    2003-04-01

    Single-flux-quantum (SFQ) technology is a novel technology where binary information is represented by a single flux. It enables us to realize high-speed, low-power SFQ logic circuits, surpassing conventional complementary metal-oxide-silicon (CMOS) technology. We proposed an SFQ packet switch to avoid the bottlenecks in broadband networks of the future. To demonstrate high-speed operation of an SFQ logic circuit and its application to our switch architecture, we designed a cross/bar switch. It consists of 13 logic gates and 581 Josephson junctions were used in the layout. We confirmed correct operations up to 33 GHz in simulation. We placed the switch circuit in an on-chip test system for high-speed (over 10 GHz) test. Including I/O circuits, the system as a whole consists of 1236 Josephson junctions. The chip was fabricated by using NEC’s standard Nb process. We carried out an on-chip test and found correct operations up to 35 GHz.

  14. Oscillations of the energy, magnetic moment, and current with a period equal to the normal or superconducting flux quantum in cyclic systems

    SciTech Connect

    Svirskii, M.S.

    1985-09-10

    Oscillations with a period equal to the normal or superconducting flux quantum occur in the current density and the orbital parts of the energy and the magnetic moment in cyclic systems. Transitions between these regimes can be induced by changing the number of electrons or by switching between states with different energies.

  15. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Conditions during passage of short optical pulses across a strongly scattering media

    NASA Astrophysics Data System (ADS)

    Tereshchenko, Sergei A.; Podgaetskii, Vitalii M.; Vorob'ev, Nikolai S.; Smirnov, A. V.

    1996-03-01

    A transient two-flux model of the interaction of light with a strongly scattering medium is developed on the basis of the concept of the paraxial photon propagating along the direction of thin pulsed laser beam incident on such a medium. An analitic expression for the radiation flux transmitted by a scattering medium is derived. Calculations are made of the dependences of the parameters of the temporal distributions of the transmitted radiation on the characteristics of the scattering medium. It is swown that the absorption and scattering coefficients of such a medium con be determined from the profile of the temporal distributions of the transmitted radiation. An experimental determination of the temporal distributions is reported for the radiation from a picosecond neodymium laser transmitted by a model scattering medium (a solution of dried milk in water). The experimental results are described well by the theoretical model.

  16. Optical properties of CdTe- Cd0.90Mn0.10Te multiple quantum well structures grown by pulsed laser evaporation and epitaxy

    NASA Astrophysics Data System (ADS)

    Dubowski, J. J.; Roth, A. P.; Deleporte, E.; Peter, G.; Feng, Z. C.; Perkowitz, S.

    1992-02-01

    Low-temperature photoluminescence, photoluminescence excitation and Raman spectroscopy measurements of CdTeCd 0.90Mn 0.10Te multiple quantum well (MQW) structures grown by pulsed laser evaporation and epitaxy (PLEE) on (001) Cd 1- xZn xTe substrates are carried out. The samples are grown from fluxes of Cd-Te and Cd-Mn-Te provided by ablation of solid CdTe and Cd 0.93Mn 0.07Te targets with Nd:YAG and excimer XeCl lasers, respectively. The excitonic lines corresponding to the quantum well E 1-HH 1 transition are investigated. Comparison between the observed PL excitonic emissions and calculated energy levels using a Kronig-Penney model with the well width as a fitting parameter allowed us to determine the "optical" well widths of the samples and to compare them with those determined from secondary ion mass spectroscopy in-depth profiles. Raman spectra for non-resonance excitation at 501.7 nm are dominated by the CdTe-like longitudinal optical (LO) modes at 166 cm -1 and MnTe-like LO modes at 194 cm -1 from the Cd 0.90Mn 0.10Te barriers. Under resonance conditions, with excitation at 476.5 nm the CdTe LO, 2LO and 3LO modes from the wells near 170,340 and 510 cm -1 dominate the spectra. The results clearly indicate that the PLEE-grown MQWs have the characteristics of the best currently available material.

  17. Effect of irrigation on short-term pulses of greenhouse gas fluxes from manure-amended soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Greenhouse gas fluxes were monitored at a no-till continuous corn field site contrasting irrigation rates (60% versus 100%), overall nitrogen fertilizer rates (125 versus 200 kg N/ha), and biennial application of cattle feedlot manure. Greenhouse gas fluxes were assessed after the manure applicatio...

  18. Modification of the quantum mechanical flux formula for electron-hydrogen ionization through Bohm's velocity field

    NASA Astrophysics Data System (ADS)

    Randazzo, J. M.; Ancarani, L. U.

    2015-12-01

    For the single differential cross section (SDCS) for hydrogen ionization by electron impact (e -H problem), we propose a correction to the flux formula given by R. Peterkop [Theory of Ionization of Atoms by Electron Impact (Colorado Associated University Press, Boulder, 1977)]. The modification is based on an alternative way of defining the kinetic energy fraction, using Bohm's definition of velocities instead of the usual asymptotic kinematical, or geometrical, approximation. It turns out that the solution-dependent, modified energy fraction is equally related to the components of the probability flux. Compared to what is usually observed, the correction yields a finite and well-behaved SDCS value in the asymmetrical situation where one of the continuum electrons carries all the energy while the other has zero energy. We also discuss, within the S -wave model of the e -H ionization process, the continuity of the SDCS derivative at the equal energy sharing point, a property not so clearly observed in published benchmark results obtained with integral and S -matrix formulas with unequal final states.

  19. Two-pulse propagation in media with quantum-mixed ground states

    SciTech Connect

    Clader, B. D.; Eberly, J. H.

    2007-11-15

    We examine fully coherent two-pulse propagation in a {lambda}-type medium, under two-photon resonance conditions and including inhomogeneous broadening. We examine the effects of both short pulse preparation and medium preparation. We contrast the cases in which the two pulses have or have not matched envelopes, and media with and without ground state coherence. We find that an extended interpretation of the area theorem for single-pulse self-induced transparency is able to unify two-pulse propagation scenarios, including some aspects of electromagnetically induced transparency and stimulated Raman scattering. We present numerical solutions of both three-level and adiabatically reduced two-level density matrix equations and Maxwell's equations, and show that many features of the solutions are quickly interpreted with the aid of analytical solutions that we also provide for restricted cases of pulse shapes and preparation of the medium. In the limit of large one-photon detuning, we show that the adiabatic two-level equations commonly used to study stimulated Raman scattering are not reliable for pulse areas in the 2{pi} range, which allows puzzling features of previous numerical work to be understood.

  20. Two-pulse propagation in media with quantum-mixed ground states

    NASA Astrophysics Data System (ADS)

    Clader, B. D.; Eberly, J. H.

    2007-11-01

    We examine fully coherent two-pulse propagation in a Λ -type medium, under two-photon resonance conditions and including inhomogeneous broadening. We examine the effects of both short pulse preparation and medium preparation. We contrast the cases in which the two pulses have or have not matched envelopes, and media with and without ground state coherence. We find that an extended interpretation of the area theorem for single-pulse self-induced transparency is able to unify two-pulse propagation scenarios, including some aspects of electromagnetically induced transparency and stimulated Raman scattering. We present numerical solutions of both three-level and adiabatically reduced two-level density matrix equations and Maxwell’s equations, and show that many features of the solutions are quickly interpreted with the aid of analytical solutions that we also provide for restricted cases of pulse shapes and preparation of the medium. In the limit of large one-photon detuning, we show that the adiabatic two-level equations commonly used to study stimulated Raman scattering are not reliable for pulse areas in the 2π range, which allows puzzling features of previous numerical work to be understood.

  1. Disorder in a quantum spin liquid: flux binding and local moment formation.

    PubMed

    Willans, A J; Chalker, J T; Moessner, R

    2010-06-11

    We study the consequences of disorder in the Kitaev honeycomb model, considering both site dilution and exchange randomness. We show that a single vacancy binds a flux and induces a local moment. This moment is polarized by an applied field h: in the gapless phase, for small h the local susceptibility diverges as χ(h)∼ln(1/h); for a pair of nearby vacancies on the same sublattice, this even increases to χ(h)∼1/(h[ln(1/h)](3/2)). By contrast, weak exchange randomness does not qualitatively alter the susceptibility but has its signature in the heat capacity, which in the gapless phase is power law in temperature with an exponent dependent on disorder strength. PMID:20867265

  2. Seasonal and spatial variations of diurnal variations of the VLF pulsed flux of the natural electromagnetic field recorded in middle latitudes

    NASA Astrophysics Data System (ADS)

    Naguslaeva, I. B.; Bashkuev, Yu. B.; Dembelov, M. G.

    2016-05-01

    A database of continuous measurements of the VLF pulsed flux of the natural electromagnetic field of the Earth (NEMFE) in southern Siberia during the period from March 31, 2008 to the present was created. Analysis of long-term continuous observations has shown that NEMFE diurnal variations have stable seasonal changes. A high interannual correlation coefficient of NEMFE diurnal variations for the same months in 2008-2014 was discovered. The analysis of data from spaced recorders has shown a high degree of spatial correlation, which indicates a single local mechanism of the NEMFE formation.

  3. Rapid-Pulsing Artifact-Free Double-Quantum-Filtered Homonuclear Spectroscopy. The 2D-INADEQUATE Experiment Revisited

    NASA Astrophysics Data System (ADS)

    Bourdonneau, Maryse; Ancian, Bernard

    1998-06-01

    Rapid pulsing artifacts are observed in the conventional phase-cycled carbon-13 2D INADEQUATE experiment. By using the product operator formalism, it is shown that they result from the effects of imperfect 90° and 180° excitation pulses on the most abundant molecules containing only one isolated carbon-13 nucleus. The labeled longitudinal magnetization remaining at the end of one scan is recycled by the subsequent acquisition, giving rise to multiple-quantum (p= 0, ±1, ±2, …) artifacts in theF1dimension. By considering pairs of scans instead of single scans, a new phase cycle is proposed. It is based on a scheme for compensating for imperfections in the excitation cluster by a proper combination of the pulse phases in two consecutive scans. Because the artifacts are 90° out of phase compared to the desired signal, a concomitant rearrangement of the receiver phase achieves suppression of all unwanted signals. Experiments are presented on menthol dissolved in CDCl3as a test compound. Improvements in spectrum quality as well as increased sensitivity are discussed.

  4. Formation of core@multi-shell CdSe@CdZnS-ZnS quantum dot heterostructure films by pulse electrophoresis deposition

    NASA Astrophysics Data System (ADS)

    Raj, Sudarsan; Yun, Jin Hyeon; Adilbish, Ganpurev; Ch, Rama Krishna; Lee, In Hwan; Lee, Min Sang; Yu, Yeon-Tae

    2015-07-01

    CdSe@CdZnS-ZnS core@multi-shell quantum dot (QD) heterostructures were deposited on fluorine doped tinoxide (FTO) glass substrate by pulse electrophoresis deposition (EPD). Field emissions scanning electron microscopy (FESEM) images reveal that the number of QDs deposited on the substrate increased with prolonged deposition time. Ethanol is the better solution medium as compared to 2-propanol for pulse electrophoresis deposition. For longer deposition time the intensity of photo luminescence (PL) peak increased.

  5. Fast-Ion Energy-Flux Enhancement from Ultrathin Foils Irradiated by Intense and High-Contrast Short Laser Pulses

    SciTech Connect

    Andreev, A.; Platonov, K.; Levy, A.; Ceccotti, T.; Thaury, C.; Loch, R. A.; Martin, Ph.

    2008-10-10

    Recent significant improvements of the contrast ratio of chirped pulse amplified pulses allows us to extend the applicability domain of laser accelerated protons to very thin targets. In this framework, we propose an analytical model particularly suitable to reproducing ion laser acceleration experiments using high intensity and ultrahigh contrast pulses. The model is based on a self-consistent solution of the Poisson equation using an adiabatic approximation for laser generated fast electrons which allows one to find the target thickness maximizing the maximum proton (and ion) energies and population as a function of the laser parameters. Model furnished values show a good agreement with experimental data and 2D particle-in-cell simulation results.

  6. Fast in situ airborne and ground-based flux measurement of ammonia using a quantum cascade laser spectrometer

    NASA Astrophysics Data System (ADS)

    Leen, J. B.; Yu, X.; Hubbe, J.; Kluzek, C. D.; Tomlinson, J. M.; Fischer, M. L.; Reichl, K.; Gupta, M.

    2012-12-01

    A pair of new ammonia (NH3) spectrometers were developed based on off-axis integrated cavity output spectroscopy. These ammonia gas analyzers consist of an optical cell, a quantum-cascade laser, a HgCdTe detector, gas sampling system, electronics for control and data acquisition, and data-analysis software. The NH3 mixing ratio is determined from high-resolution NH3 absorption line shapes by tuning the laser wavelength over the fundamental vibration band near 9.6 μm. Excellent linearity is obtained in a wide range (0- 500 ppb) with a precision of 75 ppt (1σ in 1 second). The analyzers' 1/e response time to step changes in ammonia concentration are 2.4 Hz and 8.1 Hz for the airborne and flux instruments, respectively. Feasibility was demonstrated in airborne test flights in the troposphere on board of the Department of Energy (DOE) Gulfstream-1 (G-1) aircraft. Two research flights were conducted over Sunnyside, Washington. In the first test flight, the ammonia gas sensor was used to identify signatures of feedstock from local dairy farms with high vertical spatial resolution under low wind and stable atmospheric conditions. In the second flight, the NH3 spectrometer showed high sensitivity in capturing feedstock emission signals under windy and less stable conditions. Mixing ratios aloft were measured between 0.75 ppb above the boundary layer and 100 ppb over large feedlots. Eddy covariance estimates of NH3 flux from a manure slurry amendment were performed in a pasture near Two Rock, California from May 18, 2012 to July 5, 2012. Measurement spanned pasture conditions from forage growth, cut-to-ground, manure slurry amendment (estimated to be 95 ± 33% kg NH3-N ha-1) and re-growth. An exponential decay fit to the NH3 flux data after slurry amendment provides an estimate of cumulative emission of 6.6 ± 0.5 kg NH3-N ha-1 (or 7 ± 0.24% of the total applied nitrogen) as a result of the slurry amendment. These results demonstrate that the new ammonia spectrometers

  7. Analysis of single pulse radio flux measurements of PSR B1133+16 at 4.85 and 8.35 GHz

    NASA Astrophysics Data System (ADS)

    Krzeszowski, K.; Maron, O.; Słowikowska, A.; Dyks, J.; Jessner, A.

    2014-05-01

    We show the results of microsecond resolution radio data analysis focused on flux measurements of single pulses of PSR B1133+16. The data were recorded at 4.85 and 8.35 GHz with 0.5- and 1.1-GHz bandwidth, respectively, using Radio Telescope Effelsberg (Max-Planck-Institut für Radioastronomie). The most important conclusion of the analysis is that the strongest single pulse emission at 4.85 and 8.35 GHz contributes almost exclusively to the trailing part of the leading component of the pulsar mean profile, whereas studies at lower frequencies report that the contribution is spread almost uniformly, covering all phases of the pulsar mean profile. We also estimate the radio emission heights to be around 1-2 per cent of the light-cylinder radius, which is in agreement with previous studies. Additionally, these observations allowed us to add two more measurements of the flux density to the PSR B1133+16 broad-band radio spectrum, covering frequencies from 16.7 MHz up to 32 GHz. We fit two different models to the spectrum: a broken power law and a spectrum based on the flicker-noise model, which represents the spectrum in a simpler, but similarly accurate, way.

  8. Bulk Quantum Computation with Pulsed Electron Paramagnetic Resonance: Simulations of Single-Qubit Error Correction Schemes

    NASA Astrophysics Data System (ADS)

    Ishmuratov, I. K.; Baibekov, E. I.

    2015-12-01

    We investigate the possibility to restore transient nutations of electron spin centers embedded in the solid using specific composite pulse sequences developed previously for the application in nuclear magnetic resonance spectroscopy. We treat two types of systematic errors simultaneously: (i) rotation angle errors related to the spatial distribution of microwave field amplitude in the sample volume, and (ii) off-resonance errors related to the spectral distribution of Larmor precession frequencies of the electron spin centers. Our direct simulations of the transient signal in erbium- and chromium-doped CaWO4 crystal samples with and without error corrections show that the application of the selected composite pulse sequences can substantially increase the lifetime of Rabi oscillations. Finally, we discuss the applicability limitations of the studied pulse sequences for the use in solid-state electron paramagnetic resonance spectroscopy.

  9. Quantum Derivative Fitting and Biomolecular Force Fields: Functional Form, Coupling Terms, Charge Flux, Nonbond Anharmonicity, and Individual Dihedral Potentials.

    PubMed

    Hagler, A T

    2015-12-01

    Computer simulations are increasingly prevalent, complementing experimental studies in all fields of biophysics, chemistry, and materials. Their utility, however, is critically dependent on the validity of the underlying force fields employed. In this Perspective we review the ability of quantum mechanics, and in particular analytical ab initio derivatives, to inform on the nature of intra- and intermolecular interactions. The power inherent in the exploitation of forces and second derivatives (Hessians) to derive force fields for a variety of compound types, including inorganic, organic, and biomolecules, is explored. We discuss the use of these quantities along with QM energies and geometries to determine force constants, including nonbond and electrostatic parameters, and to assess the functional form of the energy surface. The latter includes the optimal form of out-of-plane interactions and the necessity for anharmonicity, and terms to account for coupling between internals, to adequately represent the energy of intramolecular deformations. In addition, individual second derivatives of the energy with respect to selected interaction coordinates, such as interatomic distances or individual dihedral angles, have been shown to select out for the corresponding interactions, annihilating other interactions in the potential expression. Exploitation of these quantities allows one to probe the individual interaction and explore phenomena such as, for example, anisotropy of atom-atom nonbonded interactions, charge flux, or the functional form of isolated dihedral angles, e.g., a single dihedral X-C-C-Y about a tetrahedral C-C bond. PMID:26642978

  10. Quantum control of dressed state population for Li2 molecules by intense femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Han, Xiao; Zhan, Wei-Shen; Wang, Shuo; Zai, Jing-Bo; Dang, Hai-Ping

    2016-02-01

    We investigated the Autler-Townes splitting in photoelectron spectra of \\text{L}{{\\text{i}}2} molecules steered by ultrashort laser pulses using the time-dependent wave-packet method. Structure of the Autler-Townes splitting was presented to analyze the information of a selective population of the dressed states. It was found that population transfer process, structure of photoelectron spectrum and pattern of Autler-Townes splitting can be controlled by adjusting the intensity, wavelength and delay time of laser pulses.

  11. Open-path quantum cascade laser-based system for simultaneous remote sensing of methane, nitrous oxide, and water vapor using chirped-pulse differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Castillo, Paulo; Diaz, Adrian; Thomas, Benjamin; Gross, Barry; Moshary, Fred

    2015-10-01

    Methane and Nitrous Oxide are long-lived greenhouse gases in the atmosphere with significant global warming effects. We report on application of chirped-pulsed quantum cascade lasers (QCLs) to simultaneous measurements of these trace gases in both open-path fence-line and backscatter systems. The intra-pulse thermal frequency chip in a QCL can be time resolved and calibrated to allow for high resolution differential optical absorption spectroscopy over the spectral window of the chip, which for a DFB-QCL can be reach ~2cm-1 for a 500 nsec pulse. The spectral line-shape of the output from these lasers are highly stable from pulse to pulse over long period of time (> 1 day), and the system does not require frequent calibrations.

  12. CdTe-Cd1 - xMnxTe multiple quantum well structures grown by pulsed laser evaporation and epitaxy

    NASA Astrophysics Data System (ADS)

    Dubowski, J. J.; Roth, A. P.; Wasilewski, Z. R.; Rolfe, S. J.

    1991-09-01

    Structural and optical properties of (001) CdTe-Cd1-xMnxTe (x=0.10) multiple quantum well structures grown by pulsed laser evaporation and epitaxy (PLEE) are investigated. The layers are grown on (001) CdZnTe wafers held at a temperature in the range of 210-230 °C. Secondary-ion mass spectroscopy in-depth profiles reveal that highly uniform structures are grown. Numerical analysis of double crystal x-ray diffraction results demonstrates high structural quality of the layers and indicates partial relaxation of the strain in these structures. Low-temperature photoluminescence exhibits excitonic recombinations in the CdTe wells whereas photoluminescence from the Cd1-xMnxTe barriers is not observed. The chemical composition of the barriers deduced from photoluminescence is in excellent agreement with the intended chemical composition set during growth.

  13. A long-distance quantum key distribution scheme based on pre-detection of optical pulse with auxiliary state

    NASA Astrophysics Data System (ADS)

    Quan, Dong-Xiao; Zhu, Chang-Hua; Liu, Shi-Quan; Pei, Chang-Xing

    2015-05-01

    We construct a circuit based on PBS and CNOT gates, which can be used to determine whether the input pulse is empty or not according to the detection result of the auxiliary state, while the input state will not be changed. The circuit can be treated as a pre-detection device. Equipping the pre-detection device in the front of the receiver of the quantum key distribution (QKD) can reduce the influence of the dark count of the detector, hence increasing the secure communication distance significantly. Simulation results show that the secure communication distance can reach 516 km and 479 km for QKD with perfect single photon source and decoy-state QKD with weak coherent photon source, respectively. Project supported by the National Natural Science Foundation of China (Grant No. 61372076), the Programme of Introducing Talents of Discipline to Universities, China (Grant No. B08038), and the Fundamental Research Funds for the Central Universities, China (Grant No. K5051201021).

  14. Heat Flux Calculation and Problem of Flaking of Boron Carbide Coatings on the Faraday Screen of the ICRH Antennas During Tore Supra High Power, Long Pulse Operation

    SciTech Connect

    Corre, Y.; Lipa, M.; Agarici, G.; Basiuk, V.; Colas, L.; Courtois, X.; Dumont, R. J.; Ekedahl, A.; Gardarein, J. L.; Klepper, C Christopher; Martin, V.; Moncada, V.; Portafaix, C.; Rigollet, F.; Tawizgant, R.; Travere, J. M.; Valliez, K.

    2011-01-01

    Reliable and repetitive high power and long pulse tokamak operation is strongly dependant of the ability to secure the Plasma Facing Components (PFCs). In Tore Supra, a network of 7 infrared (IR) video cameras is routinely used to prevent PFCs overheating and damage in selected regions. Real time feedback control and offline analysis are essential for basic protection and understanding of abnormal thermal events. One important limitation detected by the IR real time feed-back loop during high power RF operation (injected power of 9.5 MW over 26 s and 12 MW over 10 s have been achieved respectively in 2006 and 2008) is due to the interaction between fast ions which increase the power flux density and flaking of the boron carbide coatings on the Faraday screen box of the ICRH antennas. An IR-based experimental procedure is proposed in order to detect new flakes during plasma operation. The thermal response of the B4C coating is studied with and without flaking during plasma operation. The experimental heat flux deposited by fast ion losses on the Faraday screen is calculated for high (3.8 T) and low magnetic field (2 T) during high RF power operation (with fundamental hydrogen minority and second harmonic ICRH heating schemes respectively). The paper addresses both thermal science issues applied to machine protection and limitation due to fast ions issues during high RF power, long pulse operation. Safety margin to critical heat flux and number of fatigue cycles under heat load are presented in the paper.

  15. Persistent current in a correlated quantum ring with electron-phonon interaction in the presence of Rashba interaction and Aharonov-Bohm flux.

    PubMed

    Monisha, P J; Sankar, I V; Sil, Shreekantha; Chatterjee, Ashok

    2016-01-01

    Persistent current in a correlated quantum ring threaded by an Aharonov-Bohm flux is studied in the presence of electron-phonon interactions and Rashba spin-orbit coupling. The quantum ring is modeled by the Holstein-Hubbard-Rashba Hamiltonian and the energy is calculated by performing the conventional Lang-Firsov transformation followed by the diagonalization of the effective Hamiltonian within a mean-field approximation. The effects of Aharonov-Bohm flux, temperature, spin-orbit and electron-phonon interactions on the persistent current are investigated. It is shown that the electron-phonon interactions reduce the persistent current, while the Rashba coupling enhances it. It is also shown that temperature smoothens the persistent current curve. The effect of chemical potential on the persistent current is also studied. PMID:26831831

  16. Persistent current in a correlated quantum ring with electron-phonon interaction in the presence of Rashba interaction and Aharonov-Bohm flux

    NASA Astrophysics Data System (ADS)

    Monisha, P. J.; Sankar, I. V.; Sil, Shreekantha; Chatterjee, Ashok

    2016-02-01

    Persistent current in a correlated quantum ring threaded by an Aharonov-Bohm flux is studied in the presence of electron-phonon interactions and Rashba spin-orbit coupling. The quantum ring is modeled by the Holstein-Hubbard-Rashba Hamiltonian and the energy is calculated by performing the conventional Lang-Firsov transformation followed by the diagonalization of the effective Hamiltonian within a mean-field approximation. The effects of Aharonov-Bohm flux, temperature, spin-orbit and electron-phonon interactions on the persistent current are investigated. It is shown that the electron-phonon interactions reduce the persistent current, while the Rashba coupling enhances it. It is also shown that temperature smoothens the persistent current curve. The effect of chemical potential on the persistent current is also studied.

  17. Persistent current in a correlated quantum ring with electron-phonon interaction in the presence of Rashba interaction and Aharonov-Bohm flux

    PubMed Central

    Monisha, P. J.; Sankar, I. V.; Sil, Shreekantha; Chatterjee, Ashok

    2016-01-01

    Persistent current in a correlated quantum ring threaded by an Aharonov-Bohm flux is studied in the presence of electron-phonon interactions and Rashba spin-orbit coupling. The quantum ring is modeled by the Holstein-Hubbard-Rashba Hamiltonian and the energy is calculated by performing the conventional Lang-Firsov transformation followed by the diagonalization of the effective Hamiltonian within a mean-field approximation. The effects of Aharonov-Bohm flux, temperature, spin-orbit and electron-phonon interactions on the persistent current are investigated. It is shown that the electron-phonon interactions reduce the persistent current, while the Rashba coupling enhances it. It is also shown that temperature smoothens the persistent current curve. The effect of chemical potential on the persistent current is also studied. PMID:26831831

  18. Engineering of 3D self-directed quantum dot ordering in multilayer InGaAs/GaAs nanostructures by means of flux gas composition.

    PubMed

    Lytvyn, P M; Mazur, Yu I; Marega, E; Dorogan, V G; Kladko, V P; Slobodian, M V; Strelchuk, V V; Hussein, M L; Ware, M E; Salamo, G J

    2008-12-17

    Lateral ordering of InGaAs quantum dots on the GaAs (001) surface has been achieved in earlier reports, resembling an anisotropic pattern. In this work, we present a method of breaking the anisotropy of ordered quantum dots (QDs) by changing the growth environment. We show experimentally that using As(2) molecules instead of As(4) as a background flux is efficient in controlling the diffusion of distant Ga adatoms to make it possible to produce isotropic ordering of InGaAs QDs over GaAs (001). The control of the lateral ordering of QDs under As(2) flux has enabled us to improve their optical properties. Our results are consistent with reported experimental and theoretical data for structure and diffusion on the GaAs surface. PMID:19942777

  19. Propagation of a laser pulse and electro-optic switch in a GaAs/AlGaAs quadruple-coupled quantum dot molecule nanostructure

    NASA Astrophysics Data System (ADS)

    Shiri, Jalil

    2016-05-01

    Based on a GaAs/AlGaAs quadruple-coupled quantum dot heterostructure, an optical switch for controlling superluminal and subluminal light propagation is suggested. The transient and steady state behaviour of the absorption and dispersion of a probe pulse laser field through a quadruple quantum dot molecule are studied. We show that the group velocity of a light pulse can be controlled from superluminal to subluminal, or vice versa, by controlling the tunnelling rates between the quantum dots. The required switching time is calculated and we find it to be about 8 ps. We also investigated a method for the all-optical switching of probe field absorption from a large amount to nearly zero just by applying an incoherent pumping field. We estimated the required switching time for this case to be between 3 and 14 ps.

  20. Long-range energy transfer and ionization in extended quantum systems driven by ultrashort spatially shaped laser pulses.

    PubMed

    Paramonov, Guennaddi K; Bandrauk, André D; Kühn, Oliver

    2011-05-21

    The processes of ionization and energy transfer in a quantum system composed of two distant H atoms with an initial internuclear separation of 100 atomic units (5.29 nm) have been studied by the numerical solution of the time-dependent Schrödinger equation beyond the Born-Oppenheimer approximation. Thereby it has been assumed that only one of the two H atoms was excited by temporally and spatially shaped laser pulses at various laser carrier frequencies. The quantum dynamics of the extended H-H system, which was taken to be initially either in an unentangled or an entangled ground state, has been explored within a linear three-dimensional model, including the two z coordinates of the electrons and the internuclear distance R. An efficient energy transfer from the laser-excited H atom (atom A) to the other H atom (atom B) and the ionization of the latter have been found. It has been shown that the physical mechanisms of the energy transfer as well as of the ionization of atom B are the Coulomb attraction of the laser driven electron of atom A by the proton of atom B and a short-range Coulomb repulsion of the two electrons when their wave functions strongly overlap in the domain of atom B. PMID:21487637

  1. High-energy Quantum Dynamics in Ultra-Intense Laser Pulses

    SciTech Connect

    Mueller, Carsten; Mocken, Guido R.; Hatsagortsyan, Karen Z.; Keitel, Christoph H.

    2007-11-29

    Relativistic quantum dynamics and high-energy reactions of electrons and positrons in strong laser fields are studied by theoretical means. The laser-driven phenomena addressed comprise propagation of an electronic wave packet, microscopic electron-positron collisions, and muon pair creation from a positronium atom. By way of these examples we demonstrate a variety of computational methods employed in this field of theoretical physics and discuss their respective applicability ranges.

  2. Mass fluxes and isofluxes of methane (CH4) at a New Hampshire fen measured by a continuous wave quantum cascade laser spectrometer

    NASA Astrophysics Data System (ADS)

    Santoni, Gregory W.; Lee, Ben H.; Goodrich, Jordan P.; Varner, Ruth K.; Crill, Patrick M.; McManus, J. Barry; Nelson, David D.; Zahniser, Mark S.; Wofsy, Steven C.

    2012-05-01

    We have developed a mid-infrared continuous-wave quantum cascade laser direct-absorption spectrometer (QCLS) capable of high frequency (≥1 Hz) measurements of 12CH4 and 13CH4 isotopologues of methane (CH4) with in situ 1-s RMS ? precision of 1.5 ‰ and Allan-minimum precision of 0.2 ‰. We deployed this QCLS in a well-studied New Hampshire fen to compare measurements of CH4 isoflux by eddy covariance (EC) to Keeling regressions of data from automated flux chamber sampling. Mean CH4 fluxes of 6.5 ± 0.7 mg CH4 m-2 hr-1 over two days of EC sampling in July, 2009 were indistinguishable from mean autochamber CH4 fluxes (6.6 ± 0.8 mgCH4 m-2 hr-1) over the same period. Mean ? composition of emitted CH4 calculated using EC isoflux methods was -71 ± 8 ‰ (95% C.I.) while Keeling regressions of 332 chamber closing events over 8 days yielded a corresponding value of -64.5 ± 0.8 ‰. Ebullitive fluxes, representing ˜10% of total CH4 fluxes at this site, were on average 1.2 ‰ enriched in 13C compared to diffusive fluxes. CH4 isoflux time series have the potential to improve process-based understanding of methanogenesis, fully characterize source isotopic distributions, and serve as additional constraints for both regional and global CH4 modeling analysis.

  3. Quantum theory of atoms in molecules/charge-charge flux-dipole flux models for fundamental vibrational intensity changes on H-bond formation of water and hydrogen fluoride

    SciTech Connect

    Silva, Arnaldo F.; Richter, Wagner E.; Bruns, Roy E.; Terrabuio, Luiz A.; Haiduke, Roberto L. A.

    2014-02-28

    The Quantum Theory of Atoms In Molecules/Charge-Charge Flux-Dipole Flux (QTAIM/CCFDF) model has been used to investigate the electronic structure variations associated with intensity changes on dimerization for the vibrations of the water and hydrogen fluoride dimers as well as in the water-hydrogen fluoride complex. QCISD/cc-pVTZ wave functions applied in the QTAIM/CCFDF model accurately provide the fundamental band intensities of water and its dimer predicting symmetric and antisymmetric stretching intensity increases for the donor unit of 159 and 47 km mol{sup −1} on H-bond formation compared with the experimental values of 141 and 53 km mol{sup −1}. The symmetric stretching of the proton donor water in the dimer has intensity contributions parallel and perpendicular to its C{sub 2v} axis. The largest calculated increase of 107 km mol{sup −1} is perpendicular to this axis and owes to equilibrium atomic charge displacements on vibration. Charge flux decreases occurring parallel and perpendicular to this axis result in 42 and 40 km mol{sup −1} total intensity increases for the symmetric and antisymmetric stretches, respectively. These decreases in charge flux result in intensity enhancements because of the interaction contributions to the intensities between charge flux and the other quantities. Even though dipole flux contributions are much smaller than the charge and charge flux ones in both monomer and dimer water they are important for calculating the total intensity values for their stretching vibrations since the charge-charge flux interaction term cancels the charge and charge flux contributions. The QTAIM/CCFDF hydrogen-bonded stretching intensity strengthening of 321 km mol{sup −1} on HF dimerization and 592 km mol{sup −1} on HF:H{sub 2}O complexation can essentially be explained by charge, charge flux and their interaction cross term. Atomic contributions to the intensities are also calculated. The bridge hydrogen atomic contributions alone

  4. Polarization decay of pulses of electromagnetically induced transparency on J=0→J=1→J=2 degenerate quantum transitions

    NASA Astrophysics Data System (ADS)

    Parshkov, O. M.

    2016-02-01

    The evolution of radiation under conditions of electromagnetically induced transparency in the scheme of degenerate quantum transitions J = 0 → J = 1 → J = 2 in the pulsed interaction regime of the fields and with allowance for the Doppler broadening of spectral lines has been analyzed numerically. It has been shown that, if the input coupling radiation is linearly polarized, the circularly polarized input probe pulse splits in the medium into pulses with mutually perpendicular linear polarizations. The direction of polarization of one of these pulses coincides with the direction of polarization of the input coupling field. The distance that the probe pulse travels in the medium until it completely decays decreases with a decrease in both the duration of the input probe pulse and the intensity of the input coupling radiation. A change in the power of the input probe pulse hardly affects the distance required for the decay and the velocity of propagation of linearly polarized pulses in the medium. An increase in the Doppler broadening of spectral lines leads to a decrease in this distance and, simultaneously, to an increase in the energy losses of the probe radiation. Qualitative considerations that explain the physical reason for the investigated effects have been presented.

  5. Selective ablation of atherosclerotic lesions with less thermal damage by controlling the pulse structure of a quantum cascade laser in the 5.7-µm wavelength range

    NASA Astrophysics Data System (ADS)

    Hashimura, Keisuke; Ishii, Katsunori; Awazu, Kunio

    2016-04-01

    Cholesteryl esters are the main components of atherosclerotic plaques, and they have an absorption peak at the wavelength of 5.75 µm. To realize less-invasive ablation of the atherosclerotic plaques using a quasi-continuous wave (quasi-CW) quantum cascade laser (QCL), the thermal effects on normal vessels must be reduced. In this study, we attempted to reduce the thermal effects by controlling the pulse structure. The irradiation effects on rabbit atherosclerotic aortas using macro pulse irradiation (irradiation of pulses at intervals) and conventional quasi-CW irradiation were compared. The macro pulse width and the macro pulse interval were determined based on the thermal relaxation time of atherosclerotic and normal aortas in the oscillation wavelength of the QCL. The ablation depth increased and the coagulation width decreased using macro pulse irradiation. Moreover, difference in ablation depth between the atherosclerotic and normal rabbit aortas using macro pulse irradiation was confirmed. Therefore, the QCL in the 5.7-µm wavelength range with controlling the pulse structure was effective for less-invasive laser angioplasty.

  6. Molecular Realizations of Quantum Computing 2007

    NASA Astrophysics Data System (ADS)

    Nakahara, Mikio; Ota, Yukihiro; Rahimi, Robabeh; Kondo, Yasushi; Tada-Umezaki, Masahito

    2009-06-01

    Liquid-state NMR quantum computer: working principle and some examples / Y. Kondo -- Flux qubits, tunable coupling and beyond / A. O. Niskanen -- Josephson phase qubits, and quantum communication via a resonant cavity / M. A. Sillanpää -- Quantum computing using pulse-based electron-nuclear double resonance (ENDOR): molecular spin-qubits / K. Sato ... [et al.] -- Fullerene C[symbol]: a possible molecular quantum computer / T. Wakabayashi -- Molecular magnets for quantum computation / T. Kuroda -- Errors in a plausible scheme of quantum gates in Kane's model / Y. Ota -- Yet another formulation for quantum simultaneous noncooperative bimatrix games / A. SaiToh, R. Rahimi, M. Nakahara -- Continuous-variable teleportation of single-photon states and an accidental cloning of a photonic qubit in two-channel teleportation / T. Ide.

  7. Almost sudden perturbation of a quantum system with ultrashort electric pulses

    SciTech Connect

    Lugovskoy, Andrey; Bray, Igor

    2008-02-15

    We present an alternative approach to analyze atomic behavior when an external field perturbation is not sudden for a number of states of the field-free system. It is shown that the probability amplitudes for the system to be in these states can be accurately estimated from the closed set of their integral equations. Numerical examples for an electron in a one-dimensional Coulomb potential interacting with (i) laser and (ii) half-cycle pulses are provided. Comparison with exact calculations indicates the strength of the approach.

  8. Polaron master equation theory of pulse-driven phonon-assisted population inversion and single-photon emission from quantum-dot excitons

    NASA Astrophysics Data System (ADS)

    Manson, Ross; Roy-Choudhury, Kaushik; Hughes, Stephen

    2016-04-01

    We introduce an intuitive and semianalytical polaron master equation approach to model pulse-driven population inversion and emitted single photons from a quantum dot exciton. The master equation theory allows one to identify important phonon-induced scattering rates analytically and fully includes the role of the time-dependent pump field. As an application of the theory, we first study a quantum dot driven by a time-varying laser pulse on and off resonance, showing the population inversion caused by acoustic phonon emission in direct agreement with recent experiments of Quilter et al. [Phys. Rev. Lett. 114, 137401 (2015), 10.1103/PhysRevLett.114.137401]. We then model quantum dots in weakly coupled cavities and show the difference in population response between exciton-driven and cavity-driven systems. Finally, we assess the nonresonant phonon-assisted loading scheme with a quantum dot resonantly coupled to a cavity as a deterministic single-photon source. We also compare and contrast the important single photon figures of merit with direct Rabi oscillation of the population using a resonant π pulse, and show that the resonant scheme is much more efficient.

  9. Hyperfine Quantum Beat Spectroscopy of the Cs 8p level with Pulsed Pump-Probe Technique

    NASA Astrophysics Data System (ADS)

    Bayram, Burcin; Popov, Oleg; Kelly, Stephen; Boyle, Patrick; Salsman, Andrew

    2013-05-01

    Quantum beats arising from the hyperfine interaction were measured in a three-level excitation (lambda) scheme: pump for the 6s2S1 / 2 --> 8p2P3 / 2 and stimulated emission pump (probe) for the 8p2P3 / 2 --> 5d2D5 / 2 transitions of atomic cesium. In the technique, pump laser instantaneously excites the hot atomic vapor and creates anisotropy in the 8p2P3 / 2 level, and probe laser comes after some time delay. Delaying the probe time allows us to map out the motion of the polarized atoms like a stroboscope. According to the observed evolution of the hyperfine structure dependent parameters, e.g. alignment and atomic polarization, by delaying the arrival time of the stimulated emission pump laser (SEP), precise values of the magnetic dipole and electric quadrupole coefficients are obtained with an improved precision over previous results. The usefulness of the PUMP-SEP excitation scheme for the polarization hyperfine quantum beat measurements without complications from the Doppler effect will also be discussed. The financial support of the Research Corporation under the Grant number CC7133 and MiamiUniversity, College of the Arts and Sciences are acknowledged.

  10. Microscopic Deformation of Tungsten Surfaces by High Energy and High Flux Helium/Hydrogen Particle Bombardment with Short Pulses

    NASA Astrophysics Data System (ADS)

    Tokitani, Masayuki; Yoshida, Naoaki; Tokunaga, Kazutoshi; Sakakita, Hajime; Kiyama, Satoru; Koguchi, Haruhisa; Hirano, Yoichi; Masuzaki, Suguru

    The neutral beam injection facility in the National Institute of Advanced Industrial Science and Technology was used to irradiate a polycrystalline tungsten specimen with high energy and high flux helium and hydrogen particles. The incidence energy and flux of the beam shot were 25 keV and 8.8 × 1022 particles/m2 s, respectively. The duration of each shot was approximately 30 ms, with 6 min intervals between each shot. Surface temperatures over 1800 K were attained. In the two cases of helium irradiation, total fluence of either 1.5 × 1022 He/m2 or 4.0 × 1022 He/m2 was selected. In the former case, large sized blisters with diameter of 500 nm were densely observed. While, the latter case, the blisters were disappeared and fine nanobranch structures appeared instead. Cross-sectional observations using a transmission electron microscope (TEM) with the focused ion beam (FIB) technique were performed. According to the TEM image, after irradiation with a beam shot of total fluence 4.0 × 1022 He/m2 , there were very dense fine helium bubbles in the tungsten of sizes 1-50 nm. As the helium bubbles grew the density of the tungsten matrix drastically decreased as a result of void swelling. These effects were not seen in hydrogen irradiation case.

  11. Carbon pools and fluxes in a Tibetan alpine Kobresia pygmaea pasture partitioned by coupled eddy-covariance measurements and ¹³CO₂ pulse labeling.

    PubMed

    Ingrisch, Johannes; Biermann, Tobias; Seeber, Elke; Leipold, Thomas; Li, Maoshan; Ma, Yaoming; Xu, Xingliang; Miehe, Georg; Guggenberger, Georg; Foken, Thomas; Kuzyakov, Yakov

    2015-02-01

    The Tibetan highlands host the largest alpine grassland ecosystems worldwide, bearing soils that store substantial stocks of carbon (C) that are very sensitive to land use changes. This study focuses on the cycling of photoassimilated C within a Kobresia pygmaea pasture, the dominating ecosystems on the Tibetan highlands. We investigated short-term effects of grazing cessation and the role of the characteristic Kobresia root turf on C fluxes and belowground C turnover. By combining eddy-covariance measurements with (13)CO₂ pulse labeling we applied a powerful new approach to measure absolute fluxes of assimilates within and between various pools of the plant-soil-atmosphere system. The roots and soil each store roughly 50% of the overall C in the system (76 Mg C ha(-1)), with only a minor contribution from shoots, which is also expressed in the root:shoot ratio of 90. During June and July the pasture acted as a weak C sink with a strong uptake of approximately 2 g C m(-2) d(-1) in the first half of July. The root turf was the main compartment for the turnover of photoassimilates, with a subset of highly dynamic roots (mean residence time 20 days), and plays a key role for the C cycling and C storage in this ecosystem. The short-term grazing cessation only affected aboveground biomass but not ecosystem scale C exchange or assimilate allocation into roots and soil. PMID:25461119

  12. Formation of uniform high-density and small-size Ge/Si quantum dots by scanning pulsed laser annealing of pre-deposited Ge/Si film

    NASA Astrophysics Data System (ADS)

    Qayyum, Hamza; Lu, Chieh-Hsun; Chuang, Ying-Hung; Lin, Jiunn-Yuan; Chen, Szu-yuan

    2016-05-01

    The capability to fabricate Ge/Si quantum dots with small dot size and high dot density uniformly over a large area is crucial for many applications. In this work, we demonstrate that this can be achieved by scanning a pre-deposited Ge thin layer on Si substrate with a line-focused pulsed laser beam to induce formation of quantum dots. With suitable setting, Ge/Si quantum dots with a mean height of 2.9 nm, a mean diameter of 25 nm, and a dot density of 6×1010 cm-2 could be formed over an area larger than 4 mm2. The average size of the laser-induced quantum dots is smaller while their density is higher than that of quantum dots grown by using Stranski-Krastanov growth mode. Based on the dependence of the characteristics of quantum dots on the laser parameters, a model consisting of laser-induced strain, surface diffusion, and Ostwald ripening is proposed for the mechanism underlying the formation of the Ge/Si quantum dots. The technique demonstrated could be applicable to other materials besides Ge/Si.

  13. Improvement of thermal effects to rabbit atherosclerotic aortas by macro pulse irradiation of a quantum cascade laser in the 5.7 μm wavelength range

    NASA Astrophysics Data System (ADS)

    Hashimura, Keisuke; Ishii, Katsunori; Awazu, Kunio

    2015-03-01

    Atherosclerotic plaques mainly consist of cholesteryl esters. Cholesteryl esters have an absorption peak at the wavelength of 5.75 μm originated from C=O stretching vibration mode of ester bond. Our group achieved making cutting difference between atherosclerotic lesions and normal vessels using a quantum cascade laser (QCL) in the 5.7 μm wavelength range. QCLs are relatively new types of semiconductor lasers that can emit mid-infrared range. They are sufficiently compact and have recently achieved their high-power emission. However, large thermal damage was observed because the QCL worked as a quasi-continuous wave laser due to its short pulse interval. To realize less invasive ablation by the QCL, reducing thermal effects to normal vessels is needed. In this study, we tried improving the thermal effects by changing the pulse structure. First, irradiation effects to rabbit atherosclerotic aortas by macro pulse irradiation (irradiation of pulses at intervals) and conventional continuous pulse irradiation were compared. The macro pulse width and the macro pulse interval were set to 0.54 and 12 ms, respectively, because the thermal relaxation time of rabbit normal and atherosclerotic aortas in the oscillation wavelength was 0.54-12 ms. As a result, ablation depth became longer and coagulation width became shorter by the macro pulse irradiation. In addition, cutting difference between rabbit normal and atherosclerotic aortas was observed by the macro pulse irradiation. Therefore, the macro pulse irradiation achieved the improvement of thermal effects by the QCL in the 5.7 μm wavelength range. The QCL has the potential of realizing less-invasive laser angioplasty.

  14. Quantum coherent π-electron rotations in a non-planar chiral molecule induced by using a linearly polarized UV laser pulse

    NASA Astrophysics Data System (ADS)

    Mineo, Hirobumi; Fujimura, Yuichi

    2015-06-01

    We propose an ultrafast quantum switching method of π-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2’- biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent π-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasidegenerated excited states. We also plot the time-dependent π-electron ring current, and discussed ring current transfer between two aromatic rings.

  15. Laser absorption via quantum electrodynamics cascades in counter propagating laser pulses

    NASA Astrophysics Data System (ADS)

    Grismayer, T.; Vranic, M.; Martins, J. L.; Fonseca, R. A.; Silva, L. O.

    2016-05-01

    A model for laser light absorption in electron-positron plasmas self-consistently created via QED cascades is described. The laser energy is mainly absorbed due to hard photon emission via nonlinear Compton scattering. The degree of absorption depends on the laser intensity and the pulse duration. The QED cascades are studied with multi-dimensional particle-in-cell simulations complemented by a QED module and a macro-particle merging algorithm that allows to handle the exponential growth of the number of particles. Results range from moderate-intensity regimes ( ˜ 10 PW ) where the laser absorption is negligible to extreme intensities ( > 100 PW ) where the degree of absorption reaches 80%. Our study demonstrates good agreement between the analytical model and simulations. The expected properties of the hard photon emission and the generated pair-plasma are investigated, and the experimental signatures for near-future laser facilities are discussed.

  16. Tracing explosive in solvent using quantum cascade laser with pulsed electric discharge system

    SciTech Connect

    Park, Seong-Wook; Tian, Chao; Martini, Rainer; Chen, Gang; Chen, I-chun Anderson

    2014-11-03

    We demonstrated highly sensitive detection of explosive dissolved in solvent with a portable spectroscopy system (Q-MACS) by tracing the explosive byproduct, N{sub 2}O, in combination with a pulsed electric discharge system for safe explosive decomposition. Using Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), the gas was monitored and analyzed by Q-MACS and the presence of the dissolved explosive clearly detected. While HMX presence could be identified directly in the air above the solutions even without plasma, much better results were achieved under the decomposition. The experiment results give an estimated detection limit of 10 ppb, which corresponds to a 15 pg of HMX.

  17. Eddy covariance measurements of NH3 fluxes over a natural grass land with an open-path quantum cascade laser-based sensor

    NASA Astrophysics Data System (ADS)

    Pan, D.; Benedict, K. B.; Ham, J. M.; Prenni, A. J.; Schichtel, B. A.; Collett, J. L., Jr.; Zondlo, M. A.

    2015-12-01

    NH3 is an important component of the bio-atmospheric N cycle with implications for regional air quality, human and ecosystem health degradation, and global climate change. However, measuring NH3 flux is challenging, requiring a sensor with high sensitivity (sub-ppbv), fast response time and the capability to account for NH3 adsorption effects. In this study, we address these issues with an open-path quantum-cascade-based sensor for eddy covariance (EC) measurements. Previously, our EC NH3 sensor was deployed over a feedlot in Colorado in 2013 and 2014, and the results showed the potential of the sensor to measure NH3 emissions from agricultural sources. In the summer of 2015, the sensor was installed at a remote monitoring site in Rocky Mountain National Park to measure NH3 flux over a natural grass land. During the deployment, the precision of the sensor was about 0.15 ppbv at 10 Hz, and the detection limit of the flux was estimated to be 0.7±0.5 ng NH3/s/m2. The cospectra of the NH3 flux closely resembled those of CO2 flux and sensible heat flux measured by a LI-7500 CO2 analyzer and a CSAT3 sonic anemometer. The ogive analyses indicated that the loss of NH3 fluxes due to various damping effects was about 15%. Examining initial results from a few days of measurement, the measured NH3 fluxes appear to have a strong diurnal pattern with local emissions during afternoon, a pattern not previously reported for remote grass land. The pattern is consistent with background NH3 concentration measured by PICARRO NH3 analyzer, although summertime afternoon concentration increases at the site have previously been associated with upslope transport from urban and agricultural regions to the east. The results demonstrate the sensor's capability to measure NH3 flux in low NH3 conditions and also show that more measurements are needed to investigate spatial and temporal variability of NH3 flux.

  18. Selective population transfer and creation of an arbitrary superposition between quantum states in a Λ-type four-level system by a single linearly chirped pulse

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenhua; Tian, Jin; Du, Juan

    2016-05-01

    We present a simple and robust way to execute selective population transfer and creation of an arbitrary superposition between quantum states in a Λ-type four-level system with doublet ground states driven by a single linearly chirped pulse. It is demonstrated that the population in the initial state can be completely and flexibly transferred to either of the target states by manipulating the chirp rate and detuning of the laser pulse. Besides, the formation of an arbitrary superposition between the initial state and either of the target states through properly changing the chirp rate and detuning is also exhibited. The results of this method can be useful for selective quantum coherent control in systems with multiple target states.

  19. In vivo and in vitro effects of a pulsed electromagnetic field on net calcium flux in rat calvarial bone.

    PubMed

    Spadaro, J A; Bergstrom, W H

    2002-06-01

    Although PEMF's have been found to promote fracture healing and to modulate the activity of bone cells in vitro, effects on bone metabolism are largely unexplored. A bioassay using neonatal rat calvarial bone was used to determine the early effects of a pulsing electromagnetic field (PEMF) exposure in vivo and in vitro on bone metabolic calcium exchange. Bone discs taken from whole body exposed animals (0-4 hours) show a log exposure time-dependent average increase in net Ca uptake in the 0-50% range (r2 = 0.83). This increase could be detected immediately after exposure and also after 24 hours, but not 48 hours later. Animals given whole body PEMF exposure also showed a decrease in serum calcium and did not elevate serum Ca after administration of exogenous parathyroid hormone (PTH). Bone discs from untreated rats, exposed to PEMF for 15 minutes in vitro and then assayed, showed net Ca uptake increases of a similar magnitude and also were refractory to the Ca-releasing effect of PTH. Unexposed discs responded normally to PTH by decreasing net Ca uptake. Treatment of calvarial discs with calcitonin or acetazolamide, both of which inactivate osteoclasts, made the bone refractory to further increases in Ca uptake by PEMF. These results suggest that PEMF exposure produces PTH-refractory osteoclastics and has a relatively rapid effect on increasing net bone Ca uptake, putatively due to a decrease in PTH/paracrine-mediated bone resorption. PMID:11976773

  20. Injection current dependences of electroluminescence transition energy in InGaN/GaN multiple quantum wells light emitting diodes under pulsed current conditions

    SciTech Connect

    Zhang, Feng; Ikeda, Masao Liu, Jianping; Zhang, Shuming; Zhou, Kun; Yang, Hui; Liu, Zongshun

    2015-07-21

    Injection current dependences of electroluminescence transition energy in blue InGaN/GaN multiple quantum wells light emitting diodes (LEDs) with different quantum barrier thicknesses under pulsed current conditions have been analyzed taking into account the related effects including deformation caused by lattice strain, quantum confined Stark effects due to polarization field partly screened by carriers, band gap renormalization, Stokes-like shift due to compositional fluctuations which are supposed to be random alloy fluctuations in the sub-nanometer scale, band filling effect (Burstein-Moss shift), and quantum levels in finite triangular wells. The bandgap renormalization and band filling effect occurring at high concentrations oppose one another, however, the renormalization effect dominates in the concentration range studied, since the band filling effect arising from the filling in the tail states in the valence band of quantum wells is much smaller than the case in the bulk materials. In order to correlate the carrier densities with current densities, the nonradiative recombination rates were deduced experimentally by curve-fitting to the external quantum efficiencies. The transition energies in LEDs both with 15 nm quantum barriers and 5 nm quantum barriers, calculated using full strengths of theoretical macroscopic polarization given by Barnardini and Fiorentini [Phys. Status Solidi B 216, 391 (1999)] are in excellent accordance with experimental results. The LED with 5 nm barriers has been shown to exhibit a higher transition energy and a smaller blue shift than those of LED with 15 nm barriers, which is mainly caused by the smaller internal polarization field in the quantum wells.

  1. Tapered pulse tube for pulse tube refrigerators

    DOEpatents

    Swift, Gregory W.; Olson, Jeffrey R.

    1999-01-01

    Thermal insulation of the pulse tube in a pulse-tube refrigerator is maintained by optimally varying the radius of the pulse tube to suppress convective heat loss from mass flux streaming in the pulse tube. A simple cone with an optimum taper angle will often provide sufficient improvement. Alternatively, the pulse tube radius r as a function of axial position x can be shaped with r(x) such that streaming is optimally suppressed at each x.

  2. Temperature dependent photoluminescence from ZnO/MgZnO multiple quantum wells grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Misra, P.; Sharma, T. K.; Kukreja, L. M.

    2007-07-01

    We have studied temperature dependent photoluminescence (PL) from ZnO Multiple Quantum Wells (MQWs) of different well layer thicknesses in the range ˜1-4 nm grown on (0001) sapphire by a novel in-house developed buffer assisted pulsed laser deposition. At 10 K the PL peak shifted toward blue with decreasing well layer thickness and at constant well layer thickness the PL peak shifted towards red with increasing temperature. To the best of our knowledge we have observed for the first time an efficient room temperature (RT) PL emanating from such MQWs. The red shift of the PL peak with increasing temperature has been found to be due to the band gap shrinkage in accordance with the Varshni's empirical relation. The spectral linewidth was found to increase with increasing temperature due to the scattering of excitons with acoustic and optical phonons in different temperature regimes. Both at RT and at 10 K the PL peak shifted with respect to the well layer thickness in the range of ˜3.35-˜3.68 eV with decreasing thickness in agreement with the calculated values.

  3. Pulsed voltage deposited lead selenide thin film as efficient counter electrode for quantum-dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Jin, Bin Bin; Wang, Ye Feng; Wang, Xue Qing; Zeng, Jing Hui

    2016-04-01

    Lead selenide (PbSe) thin films were deposited on fluorine doped tin oxide (FTO) glass by a facile one-step pulse voltage electrodeposition method, and used as counter electrode (CE) in CdS/CdSe quantum dot-sensitized solar cells (QDSSCs). A power conversion efficiency of 4.67% is received for the CdS/CdSe co-sensitized solar cells, which is much better than that of 2.39% received using Pt CEs. The enhanced performance is attributed to the extended absorption in the near infrared region, superior electrocatalytic activity and p-type conductivity with a reflection of the incident light at the back electrode in addition. The physical and chemical properties were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), reflectance spectra, electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements. The present work provides a facile pathway to an efficient CE in the QDSSCs.

  4. Passive decoy-state quantum key distribution using weak coherent pulses with modulator attenuation

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Bao, Wan-Su; Li, Hong-Wei; Zhou, Chun; Wang, Yang

    2015-11-01

    Passive decoy-state quantum key distribution is more desirable than the active one in some scenarios. It is also affected by the imperfections of the devices. In this paper, the influence of modulator attenuation on the passive decoy-state method is considered. We introduce and analyze the unbalanced Mach-Zehnder interferometer, briefly, and combining with the virtual source and imaginary unitary transformation, we characterize the passive decoy-state method using a weak coherent photon source with modulator attenuation. According to the attenuation parameter δ, the pass efficiencies are given. Then, the key generation rate can be acquired. From numerical simulations, it can be seen that modulator attenuation has a nonnegligible influence on the performance of passive-state QKD protocol. Based on the research, the analysis method of virtual source and imaginary unitary transformation are preferred in analyzing passive decoy state protocol, and the passive decoy-state method is better than the active one and is close to the active vacuum + weak decoy state under the condition of having the same modulator attenuation. Project supported by the National Natural Science Foundation of China (Grant No. 11304397).

  5. A quantum cascade laser absorption spectrometer devoted to the in situ measurement of atmospheric N2O and CH4 emission fluxes

    NASA Astrophysics Data System (ADS)

    Mappé, I.; Joly, L.; Durry, G.; Thomas, X.; Decarpenterie, T.; Cousin, J.; Dumelie, N.; Roth, E.; Chakir, A.; Grillon, P. G.

    2013-02-01

    This paper describes a Quantum Cascade Laser Absorption Spectrometer, called "QCLAS" that was developed to monitor in situ greenhouse gases like N2O and CH4, at high temporal resolution and with a high accuracy. The design of the laser sensor is reported as well as its performances in terms of precision error and field deployment capabilities. Finally, to demonstrate the efficiency and the robustness of QCLAS and its suitability for gas emission monitoring and for the determination of fluxes, we report the results from a field campaign, that took place in the Wallis and Futuna Islands in 2011, to investigate the impact of environmental intensive pig farming.

  6. Relationship between evapotranspiration and precipitation pulses in a semiarid rangeland estimated by moisture flux towers and MODIS vegetation indices

    USGS Publications Warehouse

    Nagler, P.L.; Glenn, E.P.; Kim, H.; Emmerich, W.; Scott, R.L.; Huxman, T. E.; Huete, A.R.

    2007-01-01

    We used moisture Bowen ratio flux tower data and the enhanced vegetation index (EVI) from the moderate resolution imaging spectrometer (MODIS) on the Terra satellite to measure and scale evapotranspiration (ET) over sparsely vegetated grassland and shrubland sites in a semiarid watershed in southeastern Arizona from 2000 to 2004. The grassland tower site had higher mean annual ET (336 mm yr-1) than the shrubland tower site (266 mm yr-1) (P<0.001). ET measured at the individual tower sites was strongly correlated with EVI (r=0.80-0.94). ET was moderately correlated with precipitation (P), and only weakly correlated with net radiation or air temperature. The strong correlation between ET and EVI, as opposed to the moderate correlation with rainfall, suggests that transpiration (T) is the dominant process controlling ET at these sites. ET could be adequately predicted from EVI and P across seasons and tower sites (r2 = 0.74) by a single multiple regression equation. The regression equation relating ET to EVI and P was used to scale ET over 25 km2 areas of grassland and shrubland around each tower site. Over the study, ratios of T to ET ranged from 0.75 to 1.0. Winter rains stimulated spring ET, and a large rain event in fall, 2000, stimulated ET above T through the following year, indicating that winter rain stored in the soil profile can be an important component of the plants' water budget during the warm season in this ecosystem. We conclude that remotely sensed vegetation indices can be used to scale ground measurements of ET over larger landscape units in semiarid ranglelands, and that the vegetation communities in this landscape effectively harvest the available precipitation over a period of years, even though precipitation patterns are variably seasonally and interannually. ?? 2007 Elsevier Ltd. All rights reserved.

  7. Relationship Between Evapotranspiration and Precipitation Pulses in a Semiarid Rangeland Estimated by Moisture Flux Towers and MODIS Vegetation Indices

    NASA Astrophysics Data System (ADS)

    Nagler, P. L.; Glenn, E. P.; Kim, H.; Emmerich, W. E.; Scott, R. L.; Huxman, T. E.; Huete, A. R.

    2007-05-01

    We used moisture Bowen ratio flux tower data and the Enhanced Vegetation Index (EVI) from the Moderate Resolution Imaging Spectrometer (MODIS) on the Terra satellite to measure and scale evapotranspiration (ET) over sparsely vegetated grassland and shrubland sites in a semiarid watershed near the Upper San Pedro River in southeastern Arizona from 2000 to 2004. The grassland tower site had higher mean annual ET (336 mm yr-1) than the shrubland tower site (266 mm yr-1) (P<0.001). ET measured at the individual tower sites was strongly correlated with EVI (r = 0.80 - 0.94). ET was moderately correlated with precipitation (P), and only weakly correlated with net radiation or air temperature. The strong correlation between ET and EVI, as opposed to the moderate correlation with rainfall, suggests that transpiration (T) is the dominant process controlling ET at these sites. ET could be adequately predicted from EVI and P across seasons and tower sites (r2 = 0.74) by a single multiple regression equation. The regression equation relating ET to EVI and P was used to scale ET over 25 km2 areas of grassland and shrubland around each tower site. Over the study, ratios of T to ET ranged from 0.75 to 1.0. Winter rains stimulated spring ET, and a large rain event in fall, 2000, stimulated ET above T through the following year, indicating that winter rain stored in the soil profile can be an important component of the plants' water budget during the warm season in this ecosystem. We conclude that remotely sensed vegetation indices can be used to scale ground measurements of ET over larger landscape units in semiarid rangelands, and that the vegetation communities in this landscape effectively harvest the available precipitation over a period of years, even though precipitation patterns are variably seasonally and interannually.

  8. The kinetics of point defects in low-power pulsed laser annealing of ion-implanted CdTe/CdMnTe double quantum well structures

    SciTech Connect

    Sands, D.; Howari, H.

    2005-10-15

    Double quantum wells of CdTe in CdMnTe were implanted with argon ions to create vacancies and interstitials. This destroyed the photoluminescence (PL) emission from the top well and reduced the intensity from the bottom well. Pulsed radiation from an excimer laser emitting at 308 nm, with a full width at half maximum pulse lengths of 26 ns, was used to anneal the implantation damage and restore the luminescence. An optimum fluence close to 50 mJ cm{sup -2} exists for laser annealing, with the best results being obtained if single pulses are employed. Prior irradiation at lower fluences prevents full recovery of the luminescence when the higher fluence pulse is applied, and irradiation at lower fluences on unimplanted material causes a reduction in the luminescence from the top well. These results are interpreted in terms of vacancy creation and annihilation during the laser pulse. Calculations of the total number of vacancies created suggest that annihilation of the Te vacancies is the limiting step in the recovery of the PL in implanted material. It is proposed that loss of material from the surface, amounting to less than a monolayer, leads to the effective diffusion of vacancies into the solid.

  9. Multi-mJ, kHz, 2.1 μm optical parametric chirped-pulse amplifier and high-flux soft x-ray high-harmonic generation.

    PubMed

    Hong, Kyung-Han; Lai, Chien-Jen; Siqueira, Jonathas P; Krogen, Peter; Moses, Jeffrey; Chang, Chun-Lin; Stein, Gregory J; Zapata, Luis E; Kärtner, Franz X

    2014-06-01

    We report on a multi-mJ 2.1 μm optical parametric chirped-pulse amplification (OPCPA) system operating at 1 kHz repetition rate, pumped by a picosecond cryogenic Yb:YAG laser, and the demonstration of soft x-ray high-harmonic generation (HHG) with a flux of ∼2×10(8)  photon/s/1% bandwidth at 160 eV in Ar. The 1 kHz cryogenic Yb:YAG pump laser amplifies pulses up to 56 mJ and delivers compressed 42 mJ, 17 ps pulses to the 2.1 μm OPCPA system. In the three-stage OPCPA chain, we have obtained up to 2.6 mJ of output energies at 2.1 μm and pulses compressed to 40 fs with good beam quality. Finally, we show cut-off extension of HHG driven by this 2.1 μm source in Ar and N2 gas cells to 190 eV with high photon flux. Our 3D propagation simulation confirms the generation of soft x-ray attosecond pulses from the experiment with Ar. PMID:24875998

  10. Drop shaped zinc oxide quantum dots and their self-assembly into dendritic nanostructures: Liquid assisted pulsed laser ablation and characterizations

    NASA Astrophysics Data System (ADS)

    Singh, Subhash C.; Gopal, Ram

    2012-01-01

    Complex nanostructures and nano-assemblies have exhibited their potential application in the fabrication of future molecular machines and molecular devices. Liquid phase pulsed laser ablation is an easy, versatile, environmental friendly and rapidly growing method for the synthesis of nanostructured materials. Nanosecond pulsed laser ablation of zinc rod placed on the bottom of glass vessel containing methanol is used to produce colloidal solution of drop shaped zinc oxide quantum dots and their self-assembly into various dendritic nanostructures. UV-vis absorption, diffuse reflectance, transmission electron microscopy, and photoluminescence spectroscopy techniques are used for the optical, microscopic, structural and defect diagnosis of obtained colloidal quantum dots and their nano-assemblies. The average length, width and aspect ratio of drop shaped zinc oxide quantum dots are 6 ± 2.4 nm, 3.5 ± 1.4 nm and 1.69 ± 0.4 nm, respectively. Careful investigation of assemblies shows that most of them have linear growth, i.e. growth in longitudinal direction is higher as compared to the transverse direction with three types of classifications as (i) linear axis symmetrical branching, (ii) linear axis asymmetrical branching and (iii) curvilinear axis asymmetrical branching. Photoluminescence spectrum has emission peaks in UV, violet, blue and green spectral region corresponding to the excitonic and various defect related emissions.

  11. Cryogenic flux-concentrator

    NASA Technical Reports Server (NTRS)

    Bailey, B. M.; Brechna, H.; Hill, D. A.

    1969-01-01

    Flux concentrator has high primary to secondary coupling efficiency enabling it to produce high magnetic fields. The device provides versatility in pulse duration, magnetic field strengths and power sources.

  12. Selective Detection of 1H NMR Resonances of CH n Groups Using a Heteronuclear Maximum-Quantum Filter and Pulsed Field Gradients

    NASA Astrophysics Data System (ADS)

    Liu, M.; Farrant, R. D.; Nicholson, J. K.; Lindon, J. C.

    A number of approaches are described for the provision of separate one-dimensional 1H NMR spectra of CH, CH 2, and CH 3 groups utilizing the natural-abundance 13C spins and based upon the selection of the maximum multiple-quantum coherences of the various groups, This sequence is termed edited maximum-quantum proton spectroscop y (MAXY) spectroscopy, The replacement of phase cycling with the application of z magnetic field gradient pulses is also demonstrated, The editing approach is demonstrated using the 1H NMR spectrum of dexamethasone in DMSO- d6 solution, Extension to a complex mixture biofluid is exemplified by the CH 3-only 1H NMR spectrum of human seminal plasma. This aid to the assignment of endogenous metabolite resonances is demonstrated to result in dramatic spectral simplification.

  13. High-peak-power pulsed operation of 2.0 μm (AlGaIn)(AsSb) quantum-well ridge waveguide diode lasers

    NASA Astrophysics Data System (ADS)

    Eichhorn, M.; Rattunde, M.; Schmitz, J.; Kaufel, G.; Wagner, J.

    2006-03-01

    We have characterized 2.0 μm (aluminium-gallium-indium)(arsenide-antimonide) quantum-well diode lasers in pulsed operation (20-60 ns). A peak power of 1.25 W could be achieved. The near-field distribution on the output facet and the spectral output have been analyzed. Single transverse mode operation can only be maintained at low pulse currents. Above a certain current limit higher order modes occur and fluctuations between these modes have been resolved on a 10 ns time scale. The threshold for thermal and optical damage was investigated for ridge waveguide widths of 6, 8, and 16 μm. No systematic damage threshold could be determined up to current densities as high as 200 kA/cm2.

  14. Pulsed laser photolysis and quantum chemical-statistical rate study of the reaction of the ethynyl radical with water vapor.

    PubMed

    Carl, Shaun A; Nguyen, Hue Minh Thi; Elsamra, Rehab M I; Nguyen, Minh Tho; Peeters, Jozef

    2005-03-15

    The rate coefficient of the gas-phase reaction C(2)H + H(2)O-->products has been experimentally determined over the temperature range 500-825 K using a pulsed laser photolysis-chemiluminescence (PLP-CL) technique. Ethynyl radicals (C(2)H) were generated by pulsed 193 nm photolysis of C(2)H(2) in the presence of H(2)O vapor and buffer gas N(2) at 15 Torr. The relative concentration of C(2)H radicals was monitored as a function of time using a CH* chemiluminescence method. The rate constant determinations for C(2)H + H(2)O were k(1)(550 K) = (2.3 +/- 1.3) x 10(-13) cm(3) s(-1), k(1)(770 K) =(7.2 +/- 1.4) x 10(-13) cm(3) s(-1), and k(1)(825 K) = (7.7 +/- 1.5) x 10(-13) cm(3) s(-1). The error in the only other measurement of this rate constant is also discussed. We have also characterized the reaction theoretically using quantum chemical computations. The relevant portion of the potential energy surface of C(2)H(3)O in its doublet electronic ground state has been investigated using density functional theory B3LYP6-311 + + G(3df,2p) and molecular orbital computations at the unrestricted coupled-cluster level of theory that incorporates all single and double excitations plus perturbative corrections for the triple excitations, along with the 6-311 + + G(3df,2p) basis set [(U)CCSD(T)6-311 + + G(3df,2p)] and using UCCSD(T)6-31G(d,p) optimized geometries. Five isomers, six dissociation products, and sixteen transition structures were characterized. The results confirm that the hydrogen abstraction producing C(2)H(2)+OH is the most facile reaction channel. For this channel, refined computations using (U)CCSD(T)6-311 + + G(3df,2p)(U)CCSD(T)6-311 + + G(d,p) and complete-active-space second-order perturbation theory/complete-active-space self-consistent-field theory (CASPT2/CASSCF) [B. O. Roos, Adv. Chem. Phys. 69, 399 (1987)] using the contracted atomic natural orbitals basis set (ANO-L) [J. Almlof and P. R. Taylor, J. Chem. Phys.86, 4070 (1987)] were performed, yielding zero

  15. Operation of Terahertz Quantum-cascade Lasers at 164 K in Pulsed Mode and at 117 K in Continuous-wave Mode

    NASA Technical Reports Server (NTRS)

    Williams, Benjamin S.; Kumar, Sushil; Hu, Qing; Reno, John L.

    2005-01-01

    We report the demonstration of a terahertz quantum-cascade laser that operates up to 164 K in pulsed mode and 117 K in continuous-wave mod e at approximately 3.0 THz. The active region was based on a resonant -phonon depopulation scheme and a metal-metal waveguide was used for modal confinement. Copper to copper thermocompression wafer bonding w as used to fabricate the waveguide, which displayed improved thermal properties compared to a previous indium-gold bonding method.

  16. Temperature driven three-dimensional ordering of InGaAs/GaAs quantum dot superlattices grown under As2 gas flux

    NASA Astrophysics Data System (ADS)

    Lytvyn, P. M.; Mazur, Yu. I.; Benamara, M.; Ware, M. E.; Dorogan, V. G.; de Souza, L. D.; Marega, E.; Teodoro, M. D.; Marques, G. E.; Salamo, G. J.

    2014-06-01

    A comprehensive microscopy analysis has been undertaken to study three-dimensional quantum dot (QD) ordering in multilayered In0.4Ga0.6As/GaAs structures grown with an As2 flux at different substrate temperatures. Atomic force microscopy, transmission electron microscopy, and photoluminescence measurements were employed to fully understand the formation of these extended dot structures. Changes in the lateral pattern of QD ordering are correlated with their vertical alignment. These correlations are analyzed in light of the inherent transformation of the wetting and spacer layers, as well as changes in the shape, strain, and composition of individual QDs. The experimental results are attributed to the anisotropy in the thermally activated surface mass transport and the relaxation of elastic stresses.

  17. Radical quantum yields from formaldehyde photolysis in the 30,400-32,890 cm(-1) (304-329 nm) spectral region: detection of radical photoproducts using pulsed laser photolysis-pulsed laser induced fluorescence.

    PubMed

    Tatum Ernest, Cheryl; Bauer, Dieter; Hynes, Anthony J

    2012-07-01

    The relative quantum yield for the production of radical products, H + HCO, from the UV photolysis of formaldehyde (HCHO) has been measured using a pulsed laser photolysis–pulsed laser induced fluorescence (PLP–PLIF) technique across the 30,400–32,890 cm(–1) (304–329 nm) spectral region of the Ã(1)A2–X̃(1)A1 electronic transition. The photolysis laser had a bandwidth of 0.09 cm(–1), which is slightly broader than the Doppler width of a rotational line of formaldehyde at 300 K (0.07 cm(–1)), and the yield spectrum shows detailed rotational structure. The H and HCO photofragments were monitored using LIF of the OH radical as a spectroscopic marker. The OH radicals were produced by rapid reaction of the H and HCO photofragments with NO2. This technique produced an “action” spectrum that at any photolysis wavelength is the product of the H + HCO radical quantum yield and HCHO absorption cross section at the photolysis wavelength and is a relative measurement. Using the HCHO absorption cross section previously obtained in this laboratory, the relative quantum yield was determined two different ways. One produced band specific yields, and the other produced yields averaged over each 100 cm(–1). Yields were normalized to a value of 0.69 at 31,750 cm(–1) based on the current recommendation of Sander et al. (Sander, S. P.; Abbatt, J.; Barker, J. R.; Burkholder, J. B.; Friedl, R. R.; Golden, D. M.; Huie, R. E.; Kolb, C. E.; Kurylo, M. J.; Moortgat, G. K.; et al. Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation No. 17; Jet Propulsion Laboratory: Pasadena, CA, USA, 2011). The resulting radical quantum yields agree well with previous experimental studies and the current JPL recommendation but show greater wavelength dependent structure. A significant decrease in the quantum yield was observed for the 5(0)(1) + 1(0)(1)4(0)(1) combination band centered at 31,125 cm(–1). This band has a low absorption cross section and

  18. Estimating Seasonal Cycles of Atmospheric CO2 and APO Resulting from Terrestrial NEE and Air-Sea O2 Fluxes using the Transcom T3L2 Pulse-Response Functions

    NASA Astrophysics Data System (ADS)

    Nevison, C. D.

    2011-12-01

    We present a method for translating modeled terrestrial net ecosystem exchange (NEE) fluxes of carbon into the corresponding annual mean cycles in atmospheric CO2. The method is based on the pulse-response functions from the Transcom 3 atmospheric tracer transport model (ATM) intercomparison. An oceanic version of the method is applied to air-sea O2 fluxes to estimate the corresponding annual mean cycles in atmospheric potential oxygen (APO). The estimated atmospheric seasonal cycles can be evaluated against observed atmospheric CO2 and APO data, which are measured at high precision at a wide range of monitoring sites and reflect the integrated impact of surface CO2 and O2 fluxes, respectively, across broad regions. The pulse-response function method is considerably faster than a full forward ATM simulation, allowing seasonal cycles from 13 different ATMS to be computed in minutes, rather than the days or weeks required for a single forward simulation. We evaluate the method against the results of full forward ATM simulations and examine the uncertainties associated with neglecting additional surface fluxes, e.g., from fossil fuel combustion, that may contribute to the observed seasonal cycles of CO2 and APO.

  19. Influence of As{sub 4} flux on the growth kinetics, structure, and optical properties of InAs/GaAs quantum dots

    SciTech Connect

    Garcia, A.; Mateo, C. M.; Defensor, M.; Salvador, A.; Hui, H. K.; Boothroyd, C. B.; Philpott, E.

    2007-10-01

    We report the effects of variations in As{sub 4} growth flux on the evolution of molecular beam epitaxy grown InAs quantum dots (QDs) and their structures and optical properties. For InAs QDs grown under As-stable conditions, evaluated through photoluminescence and atomic force microscopy (AFM) measurements, it is evident that QD size increases with As{sub 4} pressure along with improvement in size uniformity. Furthermore, transmission electron microscopy measurements for InAs layers of critical thicknesses ({approx}1.7 ML) showed decreasing QD density with increasing As{sub 4} pressure accompanied by a strong reduction in photoluminescence (PL) integral intensity. These show that high As{sub 4} fluxes suppress InAs QD formation while the decreasing PL intensity seems to indicate cluster formation that features nonradiative recombination. AFM measurements show larger and denser QDs for samples grown at higher As{sub 4} pressures. These are explained on the basis of adatom condensation during surface cooling and the influence of As{sub 4} pressure on indium incorporation.

  20. Multiple exciton generation induced enhancement of the photoresponse of pulsed-laser-ablation synthesized single-wall-carbon-nanotube/PbS-quantum-dots nanohybrids.

    PubMed

    Ka, Ibrahima; Le Borgne, Vincent; Fujisawa, Kazunori; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Ma, Dongling; El Khakani, My Ali

    2016-01-01

    The pulsed laser deposition method was used to decorate appropriately single wall carbon nanotubes (SWCNTs) with PbS quantum dots (QDs), leading to the formation of a novel class of SWCNTs/PbS-QDs nanohybrids (NHs), without resorting to any ligand engineering and/or surface functionalization. The number of laser ablation pulses (NLp) was used to control the average size of the PbS-QDs and their coverage on the SWCNTs' surface. Photoconductive (PC) devices fabricated from these SWCNTs/PbS-QDs NHs have shown a significantly enhanced photoresponse, which is found to be PbS-QD size dependent. Wavelength-resolved photocurrent measurements revealed a strong photoconductivity of the NHs in the UV-visible region, which is shown to be due to multiple exciton generation (MEG) in the PbS-QDs. For the 6.5 nm-diameter PbS-QDs (with a bandgap (Eg) = 0.86 eV), the MEG contribution of the NHs based PC devices was shown to lead to a normalized internal quantum efficiency in excess of 300% for photon energies ≥4.5Eg. While the lowest MEG threshold in our NHs based PC devices is found to be of ~2.5Eg, the MEG efficiency reaches values as high as 0.9 ± 0.1. PMID:26830452

  1. Multiple exciton generation induced enhancement of the photoresponse of pulsed-laser-ablation synthesized single-wall-carbon-nanotube/PbS-quantum-dots nanohybrids

    NASA Astrophysics Data System (ADS)

    Ka, Ibrahima; Le Borgne, Vincent; Fujisawa, Kazunori; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Ma, Dongling; El Khakani, My Ali

    2016-02-01

    The pulsed laser deposition method was used to decorate appropriately single wall carbon nanotubes (SWCNTs) with PbS quantum dots (QDs), leading to the formation of a novel class of SWCNTs/PbS-QDs nanohybrids (NHs), without resorting to any ligand engineering and/or surface functionalization. The number of laser ablation pulses (NLp) was used to control the average size of the PbS-QDs and their coverage on the SWCNTs’ surface. Photoconductive (PC) devices fabricated from these SWCNTs/PbS-QDs NHs have shown a significantly enhanced photoresponse, which is found to be PbS-QD size dependent. Wavelength-resolved photocurrent measurements revealed a strong photoconductivity of the NHs in the UV-visible region, which is shown to be due to multiple exciton generation (MEG) in the PbS-QDs. For the 6.5 nm-diameter PbS-QDs (with a bandgap (Eg) = 0.86 eV), the MEG contribution of the NHs based PC devices was shown to lead to a normalized internal quantum efficiency in excess of 300% for photon energies ≥4.5Eg. While the lowest MEG threshold in our NHs based PC devices is found to be of ~2.5Eg, the MEG efficiency reaches values as high as 0.9 ± 0.1.

  2. Multiple exciton generation induced enhancement of the photoresponse of pulsed-laser-ablation synthesized single-wall-carbon-nanotube/PbS-quantum-dots nanohybrids

    PubMed Central

    Ka, Ibrahima; Le Borgne, Vincent; Fujisawa, Kazunori; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Ma, Dongling; El Khakani, My Ali

    2016-01-01

    The pulsed laser deposition method was used to decorate appropriately single wall carbon nanotubes (SWCNTs) with PbS quantum dots (QDs), leading to the formation of a novel class of SWCNTs/PbS-QDs nanohybrids (NHs), without resorting to any ligand engineering and/or surface functionalization. The number of laser ablation pulses (NLp) was used to control the average size of the PbS-QDs and their coverage on the SWCNTs’ surface. Photoconductive (PC) devices fabricated from these SWCNTs/PbS-QDs NHs have shown a significantly enhanced photoresponse, which is found to be PbS-QD size dependent. Wavelength-resolved photocurrent measurements revealed a strong photoconductivity of the NHs in the UV-visible region, which is shown to be due to multiple exciton generation (MEG) in the PbS-QDs. For the 6.5 nm-diameter PbS-QDs (with a bandgap (Eg) = 0.86 eV), the MEG contribution of the NHs based PC devices was shown to lead to a normalized internal quantum efficiency in excess of 300% for photon energies ≥4.5Eg. While the lowest MEG threshold in our NHs based PC devices is found to be of ~2.5Eg, the MEG efficiency reaches values as high as 0.9 ± 0.1. PMID:26830452

  3. Protected Flux Pairing Qubit

    NASA Astrophysics Data System (ADS)

    Bell, Matthew; Zhang, Wenyuan; Ioffe, Lev; Gershenson, Michael

    2014-03-01

    We have studied the coherent flux tunneling in a qubit containing two submicron Josephson junctions shunted by a superinductor (a dissipationless inductor with an impedance much greater than the resistance quantum). The two low energy quantum states of this device, 0 and 1, are represented by even and odd number of fluxes in the loop, respectively. This device is dual to the charge pairing Josephson rhombi qubit. The spectrum of the device, studied by microwave spectroscopy, reflects the interference between coherent quantum phase slips in the two junctions (the Aharonov-Casher effect). The time domain measurements demonstrate the suppression of the qubit's energy relaxation in the protected regime, which illustrates the potential of this flux pairing device as a protected quantum circuit. Templeton Foundation, NSF, and ARO.

  4. Magnetic reversal dynamics of a quantum system on a picosecond timescale

    PubMed Central

    Kuznetsov, Alexey V; Soloviev, Igor I; Bakurskiy, Sergey V; Tikhonova, Olga V

    2015-01-01

    Summary We present our approach for a consistent, fully quantum mechanical description of the magnetization reversal process in natural and artificial atomic systems by means of short magnetic pulses. In terms of the simplest model of a two-level system with a magnetic moment, we analyze the possibility of a fast magnetization reversal on the picosecond timescale induced by oscillating or short unipolar magnetic pulses. We demonstrate the possibility of selective magnetization reversal of a superconducting flux qubit using a single flux quantum-based pulse and suggest a promising, rapid Λ-scheme for resonant implementation of this process. In addition, the magnetization reversal treatment is fulfilled within the framework of the macroscopic theory of the magnetic moment, which allows for the comparison and explanation of the quantum and classical behavior. PMID:26665066

  5. Magnetic reversal dynamics of a quantum system on a picosecond timescale.

    PubMed

    Klenov, Nikolay V; Kuznetsov, Alexey V; Soloviev, Igor I; Bakurskiy, Sergey V; Tikhonova, Olga V

    2015-01-01

    We present our approach for a consistent, fully quantum mechanical description of the magnetization reversal process in natural and artificial atomic systems by means of short magnetic pulses. In terms of the simplest model of a two-level system with a magnetic moment, we analyze the possibility of a fast magnetization reversal on the picosecond timescale induced by oscillating or short unipolar magnetic pulses. We demonstrate the possibility of selective magnetization reversal of a superconducting flux qubit using a single flux quantum-based pulse and suggest a promising, rapid Λ-scheme for resonant implementation of this process. In addition, the magnetization reversal treatment is fulfilled within the framework of the macroscopic theory of the magnetic moment, which allows for the comparison and explanation of the quantum and classical behavior. PMID:26665066

  6. Macroscopic quantum fluctuations of pulsed nanosecond optical parametric generation in periodically-poled LiNbO{sub 3}

    SciTech Connect

    Guan Yiyi; Haus, Joseph W.; Powers, Peter

    2005-02-01

    We present simulations and experimental results for quantum-noise-initiated emission from an optical parametric generator (OPG) fabricated from periodically poled lithium niobate. The model we employ, which includes transverse coupling effects to enable off-axis phase matching, has been successfully used for describing broadband emission spectra in OPG's and optical parametric amplifiers. The emission spectra and the quantum statistics deduced from macroscopic fluctuations are compared between simulations and experiment.

  7. Nerve-pulse interactions

    SciTech Connect

    Scott, A.C.

    1982-01-01

    Some recent experimental and theoretical results on mechanisms through which individual nerve pulses can interact are reviewed. Three modes of interactions are considered: (1) interaction of pulses as they travel along a single fiber which leads to velocity dispersion; (2) propagation of pairs of pulses through a branching region leading to quantum pulse code transformations; and (3) interaction of pulses on parallel fibers through which they may form a pulse assembly. This notion is analogous to Hebb's concept of a cell assembly, but on a lower level of the neural hierarchy.

  8. Dynamics of Individual Eruptive Pulses and their Contribution to the Total Mass Flux - Case Study of the 2nd Explosive Phase of the 2010 Eyjafjallajökull Eruption (Iceland)

    NASA Astrophysics Data System (ADS)

    Dürig, T.; Gudmundsson, M. T.; Karmann, S.; Zimanowski, B.; Dellino, P.; Rietze, M.; Büttner, R.

    2014-12-01

    The 2010 Eyjafjallajökull eruption was characterized by pulsating activity, where emissions from the vent occurred in frequent but discrete bursts with pulses in the order of seconds that then merged at higher altitude in a sustained eruption column. High resolution near-field video recordings of the vents, taken from a distance of ~850 m from 8 - 10 May (during the second explosive phase), were used as a case study to describe the mechanism of such pulsating eruptions and their contribution to the total mass flux of ash injection in the atmosphere. The dynamics of discrete overpressured jets were quantified during the intial gas thrust stage, i.e. between discharge and the height of transition into a convective buoyant regime (at ~100 m above the vent). By applying a straight-forward volumetrical calculation model, the volume and pressure history of eruptive pulses could be reconstructed. Then the mass flux of individual pulses was determined by exploiting the fact that the pressure at the transition height is known to be at ambient pressure. Based on our results we examine how to link the eruption source parameters of multiple discrete expansive jets to the overall mass eruption rate deduced by "classical" continuous ash plume models (being ~4*104 kg/s). In addition we discuss the implications for a real-time assessment of eruption source parameters by using near-field monitoring systems under pulsatory eruption conditions.

  9. Picosecond pulse amplification up to a peak power of 42  W by a quantum-dot tapered optical amplifier and a mode-locked laser emitting at 1.26 µm.

    PubMed

    Weber, Christoph; Drzewietzki, Lukas; Rossetti, Mattia; Xu, Tianhong; Bardella, Paolo; Simos, Hercules; Mesaritakis, Charis; Ruiz, Mike; Krestnikov, Igor; Livshits, Daniil; Krakowski, Michel; Syvridis, Dimitris; Montrosset, Ivo; Rafailov, Edik U; Elsäßer, Wolfgang; Breuer, Stefan

    2015-02-01

    We experimentally study the generation and amplification of stable picosecond-short optical pulses by a master oscillator power-amplifier configuration consisting of a monolithic quantum-dot-based gain-guided tapered laser and amplifier emitting at 1.26 µm without pulse compression, external cavity, gain- or Q-switched operation. We report a peak power of 42 W and a figure-of-merit for second-order nonlinear imaging of 38.5  W2 at a repetition rate of 16 GHz and an associated pulse width of 1.37 ps. PMID:25680056

  10. The Oxygen quantum yield in diverse algae and cyanobacteria is controlled by partitioning of flux between linear and cyclic electron flow within photosystem II.

    PubMed

    Ananyev, Gennady; Gates, Colin; Dismukes, G Charles

    2016-09-01

    We have measured flash-induced oxygen quantum yields (O2-QYs) and primary charge separation (Chl variable fluorescence yield, Fv/Fm) in vivo among phylogenetically diverse microalgae and cyanobacteria. Higher O2-QYs can be attained in cells by releasing constraints on charge transfer at the Photosystem II (PSII) acceptor side by adding membrane-permeable benzoquinone (BQ) derivatives that oxidize plastosemiquinone QB(-) and QBH2. This method allows uncoupling PSII turnover from its natural regulation in living cells, without artifacts of isolating PSII complexes. This approach reveals different extents of regulation across species, controlled at the QB(-) acceptor site. Arthrospira maxima is confirmed as the most efficient PSII-WOC (water oxidizing complex) and exhibits the least regulation of flux. Thermosynechococcus elongatus exhibits an O2-QY of 30%, suggesting strong downregulation. WOC cycle simulations with the most accurate model (VZAD) show that a light-driven backward transition (net addition of an electron to the WOC, distinct from recombination) occurs in up to 25% of native PSIIs in the S2 and S3 states, while adding BQ prevents backward transitions and increases the lifetime of S2 and S3 by 10-fold. Backward transitions occur in PSIIs that have plastosemiquinone radicals in the QB site and are postulated to be physiologically regulated pathways for storing light energy as proton gradient through direct PSII-cyclic electron flow (PSII-CEF). PSII-CEF is independent of classical PSI/cyt-b6f-CEF and provides an alternative proton translocation pathway for energy conversion. PSII-CEF enables variable fluxes between linear and cyclic electron pathways, thus accommodating species-dependent needs for redox and ion-gradient energy sources powered by a single photosystem. PMID:27117512

  11. A direct current superconducting quantum interference device gradiometer with a digital signal processor controlled flux-locked loop and comparison with a conventional analog feedback scheme

    SciTech Connect

    Kung, P.J.; Bracht, R.R.; Flynn, E.R.; Lewis, P.S.

    1996-01-01

    A double-washer dc superconducting quantum interference device (SQUID) gradiometer with a flux-locked loop (FLL) based on a digital signal processor (DSP) has been developed for biomagnetic applications. All of the analog electronics in the conventional FLL are replaced and implemented by the DSP except for the low-noise field-effect transistor preamplifier at the front end of the signal recovery components. The DSP performs the signal demodulation by synchronously sampling the recovered signals and applying the appropriate full wave rectification. The signals are then integrated, filtered, and applied to the output. At 4.2 K, the white flux noise of the gradiometer measured in a DSP FLL mode is about 4{mu}{phi}{sub 0}/{radical}Hz and the noise at 1 Hz is 13 {mu}{phi}{sub 0}/{radical}Hz. The corresponding noise levels in the gradiometer operated by the conventional FLL are 1.8 and 3{mu}{phi}{sub 0}/{radical}Hz. The poorer system performance in the DSP FLL compared to the analog FLL is mainly caused by the ambient field noise and interference signals picked up through the connecting cables. Additional noise is also added to the overall noise floor by the instruments employed in the DSP system in the present prototype setup. Further improvement in the noise characteristics and the dynamic behavior of the DSP SQUID gradiometer is expected when a better configuration of DSP with the associated I/O devices is implemented. Additional improvements of the DSP programs are expected by incorporating higher-order integration, adaptive control, and noise reduction schemes. {copyright} {ital 1996 American Institute of Physics.}

  12. A new time-frequency method to reveal quantum dynamics of atomic hydrogen in intense laser pulses: Synchrosqueezing transform

    SciTech Connect

    Sheu, Yae-lin; Hsu, Liang-Yan; Wu, Hau-tieng; Li, Peng-Cheng; Chu, Shih-I

    2014-11-15

    This study introduces a new adaptive time-frequency (TF) analysis technique, the synchrosqueezing transform (SST), to explore the dynamics of a laser-driven hydrogen atom at an ab initio level, upon which we have demonstrated its versatility as a new viable venue for further exploring quantum dynamics. For a signal composed of oscillatory components which can be characterized by instantaneous frequency, the SST enables rendering the decomposed signal based on the phase information inherited in the linear TF representation with mathematical support. Compared with the classical type of TF methods, the SST clearly depicts several intrinsic quantum dynamical processes such as selection rules, AC Stark effects, and high harmonic generation.

  13. Trapped field of 1.1 T without flux jumps in an MgB2 bulk during pulsed field magnetization using a split coil with a soft iron yoke

    NASA Astrophysics Data System (ADS)

    Fujishiro, H.; Mochizuki, H.; Ainslie, M. D.; Naito, T.

    2016-08-01

    MgB2 superconducting bulks have promising potential as trapped field magnets. We have achieved a trapped field of B z = 1.1 T on a high-J c MgB2 bulk at 13 K without flux jumps by pulsed field magnetization (PFM) using a split-type coil with a soft iron yoke, which is a record-high trapped field by PFM for bulk MgB2 to date. The flux jumps, which frequently took place using a solenoid-type coil during PFM, were avoided by using the split-type coil, and the B z value was enhanced by the insertion of soft iron yoke. The flux dynamics and heat generation/propagation were analyzed during PFM using a numerical simulation, in which the magnetic flux intruded and attenuated slowly in the bulk and tended to align along the axial direction due to the presence of soft iron yoke. The advantages of the split-type coil and the simultaneous use of a soft iron yoke are discussed.

  14. Quantum-Phase Resolved Mapping of Ground-State Vibrational D{sub 2} Wave Packets via Selective Depletion in Intense Laser Pulses

    SciTech Connect

    Ergler, Th.; Rudenko, A.; Schroeter, C. D.; Moshammer, R.; Ullrich, J.; Feuerstein, B.; Zrost, K.

    2006-09-08

    Applying 7 fs pump-probe pulses (780 nm, 4x10{sup 14} W/cm{sup 2}) we observe electronic ground-state vibrational wave packets in neutral D{sub 2} with a period of T=11.101(70) fs by following the internuclear separation (R-)dependent ionization with a sensitivity of {delta}{<=}0.02 A . The absolute phase of the wave packet's motion provides evidence for R-dependent depletion of the ground state by nonlinear ionization, to be the dominant preparation mechanism. A phase shift of about {pi} found between pure ionization (D{sub 2}{sup +}) and dissociation (D{sup +}+D) channels opens a pathway of quantum control.

  15. Long wavelength superluminal pulse propagation in a defect slab doped with GaAs/AlGaAs multiple quantum well nanostructure

    NASA Astrophysics Data System (ADS)

    Panahi, M.; Solookinejad, G.; Sangachin, E. Ahmadi; Asadpour, S. H.

    2015-12-01

    In this paper, long wavelength superluminal and subluminal properties of pulse propagation in a defect slab medium doped with four-level GaAs/AlGaAs multiple quantum wells (MQWs) with 15 periods of 17.5 nm GaAs wells and 15 nm Al0.3Ga0.7As barriers is theoretically discussed. It is shown that exciton spin relaxation (ESR) between excitonic states in MQWs can be used for controlling the superluminal and subluminal light transmissions and reflections at different wavelengths. We also show that reflection and transmission coefficients depend on the thickness of the slab for the resonance and nonresonance conditions. Moreover, we found that the ESR for nonresonance condition lead to superluminal light transmission and subluminal light reflection.

  16. Demonstration of single-flux-quantum readout circuits for time-of-flight mass spectrometry systems using superconducting strip ion detectors

    NASA Astrophysics Data System (ADS)

    Sano, Kyosuke; Takahashi, Yoshihiro; Yamanashi, Yuki; Yoshikawa, Nobuyuki; Zen, Nobuyuki; Ohkubo, Masataka

    2015-07-01

    We have been developing a superconducting time-of-flight mass spectrometry (TOF-MS) system that consists of a superconducting strip ion detector (SSID) and a single-flux-quantum (SFQ) time-to-digital converter. In this study, we implement a prototype TOF-MS system using an SSID and an SFQ readout circuit in which output signals from the SSID are read out by the SFQ readout circuit and output to room-temperature electronics. The SFQ readout circuit, which consists of a current discriminator, a Josephson transmission line and an SFQ/dc converter, was fabricated using the AIST Nb standard process (STP2), and installed in a 4.2 K cryostat with a meander-shaped NbN SSID measuring 200 μm square. The dark count rate for the SSID was measured as increasing exponentially with the increase in the bias current of the SSID by using the SFQ readout circuit. Mass spectrum measurements of biomolecules, Angiotensin I, which has a molecular weight of 1296 Da, were demonstrated by using the matrix-assisted laser desorption/ionization method, and a clear corresponding peak was observed in the mass spectrum.

  17. Reduction of the jitter of single-flux-quantum time-to-digital converters for time-of-flight mass spectrometry

    NASA Astrophysics Data System (ADS)

    Sano, K.; Muramatsu, Y.; Yamanashi, Y.; Yoshikawa, N.; Zen, N.; Ohkubo, M.

    2014-09-01

    We have been developing a high-resolution superconducting time-of-flight mass spectrometry (TOF-MS) system, which utilizes a superconducting strip ion detector (SSID) and a single-flux-quantum (SFQ) time-to-digital converter (TDC). The SFQ TDC can measure time intervals between multiple input signals and directly convert them into binary data. In our previous study, 24-bit SFQ TDC with a 3 × 24-bit First-In First-Out (FIFO) buffer was designed and implemented using the AIST Nb standard process 2 (STP2), whose time resolution and dynamic range are 100 ps and 1.6 ms, respectively. In this study we reduce the jitter of the TDC by using two different approaches: one uses an on-chip clock generator with an on-chip low-pass filter for reducing the noise in the bias current, and the other uses a low-jitter external clock source at room temperature. We confirmed that the jitter is reduced to less than 100 ps in the latter approach.

  18. Herbert P. Broida Prize Talk: Experimental realization of coherent control of molecular dynamics and chemical reactions with feedback-optimized laser pulses--Quantum Control of Femtochemistry

    NASA Astrophysics Data System (ADS)

    Gerber, Gustav

    2009-05-01

    By using coherent control techniques we control the behavior of quantum systems on their natural fs-time scale by applying ultrashort coherent light fields in the wavelength range from the IR to the UV. These laser pulses can be variably shaped in space and time using a laser pulse shaper consisting of a liquid-crystal display. [1] Laser-optimized femtochemistry in the gas phase and liquid phase is one field in which this new technique is successfully employed. Automated optimization of branching ratios and total product yields of gas phase photodissociation reactions as well as chemically selective molecular excitation in the liquid phase is performed [2][3]. Structural changes of a molecule in the liquid phase have been controlled by laser-optimized photoisomerization of a cyanine dye molecule [4] and of retinal in bacteriorhodopsin [5]. So far, optimal control techniques have been restricted to gas phase and condensed phase optimization experiments. Recently we have demonstrated femtosecond laser-assisted catalytic reactions on a Pd(100) single crystal surface. By applying a closed-loop optimal control scheme, we manipulate these reactions and selectively optimize the ratio of different bond-forming reaction channels, in contrast to previous quantum control experiments aiming at bond-cleavage. The results represent a first step towards selective photocatalysis of molecules. [4pt] [1] T. Baumert et al, Appl. Phys. B 65, 779 (1997)[0pt] [2] A. Assion et al, Science 282, 919(1998); T. Brixner et al, J. Mod. Opt. 50, 539 (2003)[0pt] [3] T. Brixner et al, Nature, Vol. 414, 57 (2001) and J. Chem. Phys. 118, 3692 (2003)[0pt] [4] G. Krampert et al, Phys. Rev. Lett. 94, 068305 (2005)[0pt] [5] G. Vogt et al, Chem. Phys. Lett. 433, 211 (2006) P. Nuernberger et al, Phys. Chem. Chem. Phys. 9, 2470 (2007)

  19. High peak-power picosecond pulse generation at 1.26 µm using a quantum-dot-based external-cavity mode-locked laser and tapered optical amplifier.

    PubMed

    Ding, Y; Aviles-Espinosa, R; Cataluna, M A; Nikitichev, D; Ruiz, M; Tran, M; Robert, Y; Kapsalis, A; Simos, H; Mesaritakis, C; Xu, T; Bardella, P; Rossetti, M; Krestnikov, I; Livshits, D; Montrosset, Ivo; Syvridis, D; Krakowski, M; Loza-Alvarez, P; Rafailov, E

    2012-06-18

    In this paper, we present the generation of high peak-power picosecond optical pulses in the 1.26 μm spectral band from a repetition-rate-tunable quantum-dot external-cavity passively mode-locked laser (QD-ECMLL), amplified by a tapered quantum-dot semiconductor optical amplifier (QD-SOA). The laser emission wavelength was controlled through a chirped volume Bragg grating which was used as an external cavity output coupler. An average power of 208.2 mW, pulse energy of 321 pJ, and peak power of 30.3 W were achieved. Preliminary nonlinear imaging investigations indicate that this system is promising as a high peak-power pulsed light source for nonlinear bio-imaging applications across the 1.0 μm - 1.3 μm spectral range. PMID:22714493

  20. Sub-Doppler Spectra of Infrared Hyperfine Transitions of Nitric Oxide Using a Pulse Modulated Quantum Cascade Laser: Rapid Passage, Free Induction Decay and the AC Stark Effect

    SciTech Connect

    Duxbury, Geoffrey; Kelly, James F.; Blake, Thomas A.; Langford, Nigel

    2012-05-07

    Using a low power, rapid (nsec) pulse-modulated quantum cascade (QC) laser, collective coherent effects in the 5 {micro}m spectrum of nitric oxide have been demonstrated by the observation of sub-Doppler hyperfine splitting and also Autler-Townes splitting of Doppler broadened lines. For nitrous oxide, experiments and model calculations have demonstrated that two main effects occur with ulsemodulated (chirped) quantum cascade lasers: free induction decay signals, and signals induced by rapid passage during the laser chirp. In the open shell molecule, NO, in which both {Lambda}-doubling splitting and hyperfine structure occur, laser field-induced coupling between the hyperfine levels of the two {Lambda}-doublet components can induce a large AC Stark effect. This may be observed as sub-Doppler structure, field-induced splittings, or Autler-Townes splitting of a Doppler broadened line. These represent an extension of the types of behaviour observed in the closed shell molecule nitrous oxide, using the same apparatus, when probed with an 8 {micro}m QC laser.

  1. Low-power broadband homonuclear dipolar recoupling in MAS NMR by two-fold symmetry pulse schemes for magnetization transfers and double-quantum excitation

    NASA Astrophysics Data System (ADS)

    Teymoori, Gholamhasan; Pahari, Bholanath; Edén, Mattias

    2015-12-01

    We provide an experimental, numerical, and high-order average Hamiltonian evaluation of an open-ended series of homonuclear dipolar recoupling sequences, SR2 2p 1 with p = 1, 2, 3, … . While operating at a very low radio-frequency (rf) power, corresponding to a nutation frequency of 1/2 of the magic-angle spinning (MAS) rate (ωnut =ωr / 2), these recursively generated double-quantum (2Q) dipolar recoupling schemes offer a progressively improved compensation to resonance offsets and rf inhomogeneity for increasing pulse-sequence order p. The excellent recoupling robustness to these experimental obstacles, as well as to CSA, is demonstrated for 2Q filtering (2QF) experiments and for driving magnetization transfers in 2D NMR correlation spectroscopy, where the sequences may provide either double or zero quantum dipolar Hamiltonians during mixing. Experimental and numerical demonstrations, which mostly target conditions of "ultra-fast" MAS (≳50 kHz) and high magnetic fields, are provided for recoupling of 13C across a wide range of isotropic and anisotropic chemical shifts, as well as dipolar coupling constants, encompassing [2,3-13C2 ]alanine, [1,3-13C2 ]alanine, diammonium [1,4-13C2 ]fumarate, and [U-13 C]tyrosine. When compared at equal power levels, a superior performance is observed for the SR2p 1 sequences with p ⩾ 3 relative to existing and well-established 2Q recoupling techniques. At ultra-fast MAS, proton decoupling is redundant during the homonuclear dipolar recoupling of dilute spins in organic solids, which renders the family of SR2p 1 schemes the first efficient 2Q recoupling option for general applications, such as 2Q-1Q correlation NMR and high-order multiple-quantum excitation, under truly low-power rf conditions.

  2. Low-power broadband homonuclear dipolar recoupling in MAS NMR by two-fold symmetry pulse schemes for magnetization transfers and double-quantum excitation.

    PubMed

    Teymoori, Gholamhasan; Pahari, Bholanath; Edén, Mattias

    2015-12-01

    We provide an experimental, numerical, and high-order average Hamiltonian evaluation of an open-ended series of homonuclear dipolar recoupling sequences, SR [Formula: see text] with p=1,2,3,…. While operating at a very low radio-frequency (rf) power, corresponding to a nutation frequency of 1/2 of the magic-angle spinning (MAS) rate (ωnut=ωr/2), these recursively generated double-quantum (2Q) dipolar recoupling schemes offer a progressively improved compensation to resonance offsets and rf inhomogeneity for increasing pulse-sequence order p. The excellent recoupling robustness to these experimental obstacles, as well as to CSA, is demonstrated for 2Q filtering (2QF) experiments and for driving magnetization transfers in 2D NMR correlation spectroscopy, where the sequences may provide either double or zero quantum dipolar Hamiltonians during mixing. Experimental and numerical demonstrations, which mostly target conditions of "ultra-fast" MAS (≳50kHz) and high magnetic fields, are provided for recoupling of (13)C across a wide range of isotropic and anisotropic chemical shifts, as well as dipolar coupling constants, encompassing [2,3-(13)C2]alanine, [1,3-(13)C2]alanine, diammonium [1,4-(13)C2]fumarate, and [U-(13)C]tyrosine. When compared at equal power levels, a superior performance is observed for the SR [Formula: see text] sequences with p⩾3 relative to existing and well-established 2Q recoupling techniques. At ultra-fast MAS, proton decoupling is redundant during the homonuclear dipolar recoupling of dilute spins in organic solids, which renders the family of SR [Formula: see text] schemes the first efficient 2Q recoupling option for general applications, such as 2Q-1Q correlation NMR and high-order multiple-quantum excitation, under truly low-power rf conditions. PMID:26515279

  3. Femtosecond measurements of near-infrared pulse induced mid-infrared transmission modulation of quantum cascade lasers

    SciTech Connect

    Cai, Hong; Liu, Sheng; Lalanne, Elaine; Guo, Dingkai; Chen, Xing; Choa, Fow-Sen; Wang, Xiaojun; Johnson, Anthony M.

    2014-05-26

    We temporally resolved the ultrafast mid-infrared transmission modulation of quantum cascade lasers (QCLs) using a near-infrared pump/mid-infrared probe technique at room temperature. Two different femtosecond wavelength pumps were used with photon energy above and below the quantum well (QW) bandgap. The shorter wavelength pump modulates the mid-infrared probe transmission through interband transition assisted mechanisms, resulting in a high transmission modulation depth and several nanoseconds recovery lifetime. In contrast, pumping with a photon energy below the QW bandgap induces a smaller transmission modulation depth but much faster (several picoseconds) recovery lifetime, attributed to intersubband transition assisted mechanisms. The latter ultrafast modulation (>60 GHz) could provide a potential way to realize fast QCL based free space optical communication.

  4. The pulse of a montane ecosystem: coupled diurnal cycles in solar flux, snowmelt, evapotranspiration, groundwater, and streamflow at Sagehen Creek (Sierra Nevada, California)

    NASA Astrophysics Data System (ADS)

    Kirchner, James

    2016-04-01

    Forested catchments in the subalpine snow zone provide interesting opportunities to study the interplay between energy and water fluxes under seasonally variable degrees of forcing by transpiration and snowmelt. In such catchments, diurnal cycles in solar flux drive snowmelt and evapotranspiration, which in turn lead to diurnal cycles (with opposing phases) in groundwater levels. These in turn are linked to diurnal cycles in stream stage and discharge, which potentially provide a spatially integrated measure of snowmelt and evapotranspiration rates in the surrounding landscape. Here I analyze ecohydrological controls on diurnal stream and groundwater fluctuations induced by snowmelt and evapotranspiration (ET) at Sagehen Creek, in the Sierra Nevada mountains of California. There is a clear 6-hour lag between radiation forcing and the stream or groundwater response. This is not a travel-time delay, but instead a 90-degree dynamical phase lag arising from the integro-differential relationship between groundwater storage and recharge, ET, and streamflow. The time derivative of groundwater levels is strongly positively correlated with solar flux during snowmelt periods, reflecting snowmelt recharge to the riparian aquifer during daytime. Conversely, this derivative is strongly negatively correlated with solar flux during snow-free summer months, reflecting transpiration withdrawals from the riparian aquifer. As the snow cover disappears, the correlation between the solar flux and the time derivative of groundwater levels abruptly shifts from positive (snowmelt dominance) to negative (ET dominance). During this transition, the groundwater cycles briefly vanish when the opposing forcings (snowmelt and ET) are of equal magnitude, and thus cancel each other out. Stream stage fluctuations integrate these relationships over the altitude range of the catchment. Rates of rise and fall in stream stage are positively correlated with solar flux when the whole catchment is snow

  5. The Use of Ultrashort Picosecond Laser Pulses to Generate Quantum Optical Properties of Single Molecules in Biophysics

    NASA Astrophysics Data System (ADS)

    Ly, Sonny

    Generation of quantum optical states from ultrashort laser-molecule interactions have led to fascinating discoveries in physics and chemistry. In recent years, these interactions have been extended to probe phenomena in single molecule biophysics. Photons emitted from a single fluorescent molecule contains important properties about how the molecule behave and function in that particular environment. Analysis of the second order coherence function through fluorescence correlation spectroscopy plays a pivotal role in quantum optics. At very short nanosecond timescales, the coherence function predicts photon antibunching, a purely quantum optical phenomena which states that a single molecule can only emit one photon at a time. Photon antibunching is the only direct proof of single molecule emission. From the nanosecond to microsecond timescale, the coherence function gives information about rotational diffusion coefficients, and at longer millisecond timescales, gives information regarding the translational diffusion coefficients. In addition, energy transfer between molecules from dipole-dipole interaction results in FRET, a highly sensitive method to probe conformational dynamics at nanometer distances. Here I apply the quantum optical techniques of photon antibunching, fluorescence correlation spectroscopy and FRET to probe how lipid nanodiscs form and function at the single molecule level. Lipid nanodiscs are particles that contain two apolipoprotein (apo) A-I circumventing a lipid bilayer in a belt conformation. From a technological point of view, nanodiscs mimics a patch of cell membrane that have recently been used to reconstitute a variety of membrane proteins including cytochrome P450 and bacteriorhodopsin. They are also potential drug transport vehicles due to its small and stable 10nm diameter size. Biologically, nanodiscs resemble to high degree, high density lipoproteins (HDL) in our body and provides a model platform to study lipid-protein interactions

  6. Robustness of superconducting quantum modes against direct quasiparticle injection

    NASA Astrophysics Data System (ADS)

    Patel, U.; Nsanzineza, I.; Vavilov, M. G.; Plourde, B. L. T.; McDermott, R.

    Classical Josephson digital logic based on Single Flux Quantum (SFQ) pulses offers a path to high-fidelity coherent control of large-scale superconducting quantum machines. However, an SFQ pulse driver generates nonequilibrium quasiparticles that contribute to qubit relaxation, and steps must be taken to protect the qubit from this decoherence channel. Here we describe experiments to characterize the robustness of high-Q superconducting linear resonators and qubits against direct quasiparticle injection. We use NIS junctions and SFQ elements to controllably inject quasiparticles into the groundplane of superconducting resonator and qubit chips, and we characterize the quasiparticle contribution to dissipation. We examine the effectiveness of groundplane cuts, normal metal quasiparticle traps, and spatially-varying superconducting gaps at protecting the quantum modes against quasiparticle loss. Finally, we discuss strategies for the integration of multiqubit circuits with on-chip SFQ control elements.

  7. 10-W pulsed operation of substrate emitting photonic-crystal quantum cascade laser with very small divergence.

    PubMed

    Yao, Dan-Yang; Zhang, Jin-Chuan; Cathabard, Olivier; Zhai, Shen-Qiang; Liu, Ying-Hui; Jia, Zhi-Wei; Liu, Feng-Qi; Wang, Zhan-Guo

    2015-01-01

    High-power broad area substrate emitting photonic-crystal distributed feedback (DFB) quantum cascade lasers (QCLs) emitting around 4.73 μm is reported. Two-dimensional centered rectangular photonic-crystal (CRPC) grating is introduced to enhance optical coherence in large area device. Main lobe far-field radiation pattern with a very small divergence angle of about 0.65° × 0.31° is obtained. A record peak output power for vertical emitting QCLs exceeding 10 W is obtained with high reflectivity (HR) coating. Robust single longitudinal mode emission with a side mode suppression ratio (SMSR) of 30 dB is continuously tunable by the heat sink temperature up to 65°C. PMID:25977652

  8. Femtosecond polarization pulse shaping.

    PubMed

    Brixner, T; Gerber, G

    2001-04-15

    We report computer-controlled femtosecond polarization pulse shaping where intensity, momentary frequency, and light polarization are varied as functions of time. For the first time to our knowledge, a pulse shaper is used to modulate the degree of ellipticity as well as the orientation of the elliptical principal axes within a single laser pulse by use of a 256-pixel two-layer liquid-crystal display inside a zero-dispersion compressor. Interferometric stability of the setup is not required. Complete pulse characterization is achieved by dual-channel spectral interferometry. This technology has a large range of applications, especially in the field of quantum control. PMID:18040384

  9. Pulsed laser deposition of CuInS2 quantum dots on one-dimensional TiO2 nanorod arrays and their photoelectrochemical characteristics

    NASA Astrophysics Data System (ADS)

    Han, Minmin; Chen, Wenyuan; Guo, Hongjian; Yu, Limin; Li, Bo; Jia, Junhong

    2016-06-01

    In the typical solution-based synthesis of colloidal quantum dots (QDs), it always resorts to some surface treatment, ligand exchange processing or post-synthesis processing, which might involve some toxic chemical regents injurious to the performance of QD sensitized solar cells. In this work, the CuInS2 QDs are deposited on the surface of one-dimensional TiO2 nanorod arrays by the pulsed laser deposition (PLD) technique. The CuInS2 QDs are coated on TiO2 nanorods without any ligand engineering, and the performance of the obtained CuInS2 QD sensitized solar cells is optimized by adjusting the laser energy. An energy conversion efficiency of 3.95% is achieved under one sun illumination (AM 1.5, 100 mW cm-2). The improved performance is attributed to enhanced absorption in the longer wavelength region, quick interfacial charge transfer and few chance of carrier recombination with holes for CuInS2 QD-sensitized solar cells. Moreover, the photovoltaic device exhibits high stability in air without any specific encapsulation. Thus, the PLD technique could be further applied for the fabrication of QDs or other absorption materials.

  10. Selective ablation of rabbit atherosclerotic plaque with less thermal effect by the control of pulse structure of a quantum cascade laser in the 5.7 μm wavelength range

    NASA Astrophysics Data System (ADS)

    Hashimura, Keisuke; Ishii, Katsunori; Awazu, Kunio

    2016-03-01

    Cholesteryl esters are main components of atherosclerotic plaques and have an absorption peak at the wavelength of 5.75 μm originated from C=O stretching vibration mode of ester bond. Our group achieved the selective ablation of atherosclerotic lesions using a quantum cascade laser (QCL) in the 5.7 μm wavelength range. QCLs are relatively new types of semiconductor lasers that can emit mid-infrared range. They are sufficiently compact and considered to be useful for clinical application. However, large thermal effects were observed because the QCL worked as quasicontinuous wave (CW) lasers due to its short pulse interval. Then we tried macro pulse irradiation (irradiation of pulses at intervals) of the QCL and achieved effective ablation with less-thermal effects than conventional quasi-CW irradiation. However, lesion selectivity might be changed by changing pulse structure. Therefore, in this study, irradiation effects of the macro pulse irradiation to rabbit atherosclerotic plaque and normal vessel were compared. The macro pulse width and the macro pulse interval were set to 0.5 and 12 ms, respectively, because the thermal relaxation time of rabbit normal and atherosclerotic aortas in the oscillation wavelength of the QCL was 0.5-12 ms. As a result, cutting difference was achieved between rabbit atherosclerotic and normal aortas by the macro pulse irradiation. Therefore, macro pulse irradiation of a QCL in the 5.7 μm wavelength range is effective for reducing thermal effects and selective ablation of the atherosclerotic plaque. QCLs have the potential of realizing less-invasive laser angioplasty.

  11. Ultrafast quantum spin-state switching in the Co-octaethylporphyrin molecular magnet with a terahertz pulsed magnetic field

    NASA Astrophysics Data System (ADS)

    Farberovich, Oleg V.; Mazalova, Victoria L.

    2016-05-01

    Molecular spin crossover switches are the objects of intense theoretical and experimental studies in recent years. This interest is due to the fact that these systems allow one to control their spin state by applying an external photo-, thermo-, piezo-, or magnetic stimuli. The greatest amount of research is currently devoted to the study of the effect of the photoexcitation on the bi-stable states of spin crossover single molecular magnets (SMMs). The main limitation of photo-induced bi-stable states is their short lifetime. In this paper we present the results of a study of the spin dynamics of the Co-octaethylporphyrin (CoOEP) molecule in the Low Spin (LS) state and the High Spin (HS) state induced by applying the magnetic pulse of 36.8 T. We show that the spin switching in case of the HS state of the CoOEP molecule is characterized by a long lifetime and is dependent on the magnitude and duration of the applied field. Thus, after applying an external stimuli the system in the LS state after the spin switching reverts to its ground state, whereas the system in the HS state remains in the excited state for a long time. We found that the temperature dependency of magnetic susceptibility shows an abrupt thermal spin transition between two spin states at 40 K. Here the proposed theoretical approach opens the way to create modern devices for spintronics with the controllable spin switching process.

  12. Innovative uses of X-ray FEL and the pulsed magnets: High magnetic field X-ray scattering studies on quantum materials

    NASA Astrophysics Data System (ADS)

    Jang, H.; Nojiri, H.; Gerber, S.; Lee, W.-S.; Zhu, D.; Lee, J.-S.; Kao, C.-C.

    X-ray scattering under high magnetic fields provides unique opportunities for solving many scientific puzzles in quantum materials, such as strongly correlated electron systems. Incorporating high magnetic field capability presents serious challenges at an x-ray facility, including the limitation on the maximum magnetic field even with a DC magnet (up to ~20 Tesla), expensive cost in development, radiation damage, and limited flexibility in the experimental configuration. These challenges are especially important when studying the symmetry broken state induced by the high magnetic field are necessary, for example, exploring intertwined orders between charge density wave (CDW) and high Tc superconductivity. Moreover, a gap in magnetic field strengths has led to many discrepancies and puzzling issues for understanding strongly correlated systems - is a CDW competing or more intimately intertwined with high-temperature superconductivity. To bridge this gap and resolve these experimental discrepancies, one needs an innovative experimental approach. Here, we will present a new approach to x-ray scattering under high magnetic field up to 28 Teals by taking advantage of brilliant x-ray free electron laser (FEL). The FEL generates sufficiently high photon flux for single shot x-ray scattering experiment. In this talk, we will also present the first demonstration about the field induced CDW order in YBCO Ortho-VIII with 28 Tesla, which show the totally unexpected three-dimensional behavior.

  13. 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. PMID:22825199

  14. Highly indistinguishable photons from deterministic quantum-dot microlenses utilizing three-dimensional in situ electron-beam lithography

    NASA Astrophysics Data System (ADS)

    Gschrey, M.; Thoma, A.; Schnauber, P.; Seifried, M.; Schmidt, R.; Wohlfeil, B.; Krüger, L.; Schulze, J.-H.; Heindel, T.; Burger, S.; Schmidt, F.; Strittmatter, A.; Rodt, S.; Reitzenstein, S.

    2015-07-01

    The success of advanced quantum communication relies crucially on non-classical light sources emitting single indistinguishable photons at high flux rates and purity. We report on deterministically fabricated microlenses with single quantum dots inside which fulfil these requirements in a flexible and robust quantum device approach. In our concept we combine cathodoluminescence spectroscopy with advanced in situ three-dimensional electron-beam lithography at cryogenic temperatures to pattern monolithic microlenses precisely aligned to pre-selected single quantum dots above a distributed Bragg reflector. We demonstrate that the resulting deterministic quantum-dot microlenses enhance the photon-extraction efficiency to (23+/-3)%. Furthermore we prove that such microlenses assure close to pure emission of triggered single photons with a high degree of photon indistinguishability up to (80+/-7)% at saturation. As a unique feature, both single-photon purity and photon indistinguishability are preserved at high excitation power and pulsed excitation, even above saturation of the quantum emitter.

  15. Superradiance and flux conservation

    NASA Astrophysics Data System (ADS)

    Boonserm, Petarpa; Ngampitipan, Tritos; Visser, Matt

    2014-09-01

    The theoretical foundations of the phenomenon known as superradiance still continue to attract considerable attention. Despite many valiant attempts at pedagogically clear presentations, the effect nevertheless still continues to generate some significant confusion. Part of the confusion arises from the fact that superradiance in a quantum field theory context is not the same as superradiance (superfluorescence) in some condensed matter contexts; part of the confusion arises from traditional but sometimes awkward normalization conventions, and part is due to sometimes unnecessary confusion between fluxes and probabilities. We shall argue that the key point underlying the effect is flux conservation (and, in the presence of dissipation, a controlled amount of flux nonconservation), and that attempting to phrase things in terms of reflection and transmission probabilities only works in the absence of superradiance. To help clarify the situation we present a simple exactly solvable toy model exhibiting both superradiance and damping.

  16. Lectures on pulsed NMR

    SciTech Connect

    Pines, A.

    1988-08-01

    These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 32 refs., 56 figs.

  17. Lectures on pulsed NMR

    SciTech Connect

    Pines, A.

    1986-09-01

    These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 55 figs.

  18. Photoconductivity of Er-doped InAs quantum dots embedded in strain-relaxed InGaAs layers with 1.5 µm cw and pulse excitation

    NASA Astrophysics Data System (ADS)

    Murakumo, Keisuke; Yamaoka, Yuya; Kumagai, Naoto; Kitada, Takahiro; Isu, Toshiro

    2016-04-01

    We fabricated a photoconductive antenna structure utilizing Er-doped InAs quantum dot layers embedded in strain-relaxed In0.35Ga0.65As layers on a GaAs substrate. Mesa-shaped electrodes for the antenna structure were formed by photolithography and wet etching in order to suppress its dark current. We measured the photocurrent with the excitation of ∼1.5 µm cw and femtosecond pulse lasers. Compared with the dark current, the photocurrent was clearly observed under both cw and pulse excitation conditions and almost linearly increased with increasing excitation power in a wide range of magnitudes from 10 W/cm2 to 10 MW/cm2 order.

  19. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Reflection of an electromagnetic pulse from a subcritical waveguide taper and from a supercritical-density plasma in a waveguide

    NASA Astrophysics Data System (ADS)

    Rukhadze, Anri A.; Tarakanov, V. P.

    2006-09-01

    Two related problems are studied by numerical simulations using the KARAT code: the reflection of the TM01 mode of an electromagnetic pulse from the subcritical taper of the section of a circular waveguide and the reflection of the same pulse from a 'cold' collisionless plasma with a density increasing up to a supercritical value along the waveguide axis. It is shown that in the former case the pulse is totally reflected with an insignificant distortion of its shape, in accordance with the linear theory. In the latter case, the character of reflection depends substantially on the plasma density increase length, the pulse duration, and the wave field amplitude, a significant field deceleration and amplitude growth occurring near the critical point; the pulse absorption in the plasma far exceeds the absorption due to the linear transformation of the incident transverse wave to the longitudinal plasma oscillations.

  20. Scalable optical quantum computer

    SciTech Connect

    Manykin, E A; Mel'nichenko, E V

    2014-12-31

    A way of designing a scalable optical quantum computer based on the photon echo effect is proposed. Individual rare earth ions Pr{sup 3+}, regularly located in the lattice of the orthosilicate (Y{sub 2}SiO{sub 5}) crystal, are suggested to be used as optical qubits. Operations with qubits are performed using coherent and incoherent laser pulses. The operation protocol includes both the method of measurement-based quantum computations and the technique of optical computations. Modern hybrid photon echo protocols, which provide a sufficient quantum efficiency when reading recorded states, are considered as most promising for quantum computations and communications. (quantum computer)

  1. Time-Resolved Quantum Dynamics of Double Ionization in Strong Laser Fields

    NASA Astrophysics Data System (ADS)

    Prauzner-Bechcicki, Jakub S.; Sacha, Krzysztof; Eckhardt, Bruno; Zakrzewski, Jakub

    2007-05-01

    Quantum calculations of a (1+1)-dimensional model for double ionization in strong laser fields are used to trace the time evolution from the ground state through ionization and rescattering to the two-electron escape. The subspace of symmetric escape, a prime characteristic of nonsequential double ionization, remains accessible by a judicious choice of 1D coordinates for the electrons. The time-resolved ionization fluxes show the onset of single and double ionization, the sequence of events during the pulse, and the influences of pulse duration and reveal the relative importance of sequential and nonsequential double ionization, even when ionization takes place during the same field cycle.

  2. Time-Resolved Quantum Dynamics of Double Ionization in Strong Laser Fields

    SciTech Connect

    Prauzner-Bechcicki, Jakub S.; Sacha, Krzysztof; Zakrzewski, Jakub; Eckhardt, Bruno

    2007-05-18

    Quantum calculations of a (1+1)-dimensional model for double ionization in strong laser fields are used to trace the time evolution from the ground state through ionization and rescattering to the two-electron escape. The subspace of symmetric escape, a prime characteristic of nonsequential double ionization, remains accessible by a judicious choice of 1D coordinates for the electrons. The time-resolved ionization fluxes show the onset of single and double ionization, the sequence of events during the pulse, and the influences of pulse duration and reveal the relative importance of sequential and nonsequential double ionization, even when ionization takes place during the same field cycle.

  3. A transformer of closely spaced pulsed waveforms

    NASA Technical Reports Server (NTRS)

    Niedra, J.

    1970-01-01

    Passive circuit, using diodes, transistors, and magnetic cores, transforms the voltage of repetitive positive or negative pulses. It combines a pulse transformer with switching devices to effect a resonant flux reset and can transform various pulsed waveforms that have a nonzero average value and are relatively cosely spaced in time.

  4. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Dynamics of splashing of molten metals during irradiation with single CO2 laser pulses

    NASA Astrophysics Data System (ADS)

    Arutyunyan, R. V.; Baranov, V. Yu; Bol'shov, Leonid A.; Dolgov, V. A.; Malyuta, D. D.; Mezhevov, V. S.; Semak, V. V.

    1988-03-01

    An experimental investigation was made of the dynamics of the loss of the melt as a result of interaction with single-mode CO2 laser radiation pulses of 5-35 μs duration. The dynamics of splashing of the melt during irradiation with short pulses characterized by a Gaussian intensity distribution differed from that predicted by models in which the distribution of the vapor pressure was assumed to be radially homogeneous.

  5. Quantum Chaos

    NASA Astrophysics Data System (ADS)

    Casati, Giulio; Chirikov, Boris

    2006-11-01

    Preface; Acknowledgments; Introduction: 1. The legacy of chaos in quantum mechanics G. Casati and B. V. Chirikov; Part I. Classical Chaos and Quantum Localization: 2. Stochastic behaviour of a quantum pendulum under a periodic perturbation G. Casati, B. V. Chirikov, F. M. Izrailev and J. Ford; 3. Quantum dynamics of a nonintegrable system D. R. Grempel, R. E. Prange and S. E. Fishman; 4. Excitation of molecular rotation by periodic microwave pulses. A testing ground for Anderson localization R. Blümel, S. Fishman and U. Smilansky; 5. Localization of diffusive excitation in multi-level systems D. K. Shepelyansky; 6. Classical and quantum chaos for a kicked top F. Haake, M. Kus and R. Scharf; 7. Self-similarity in quantum dynamics L. E. Reichl and L. Haoming; 8. Time irreversibility of classically chaotic quantum dynamics K. Ikeda; 9. Effect of noise on time-dependent quantum chaos E. Ott, T. M. Antonsen Jr and J. D. Hanson; 10. Dynamical localization, dissipation and noise R. F. Graham; 11. Maximum entropy models and quantum transmission in disordered systems J.-L. Pichard and M. Sanquer; 12. Solid state 'atoms' in intense oscillating fields M. S. Sherwin; Part II. Atoms in Strong Fields: 13. Localization of classically chaotic diffusion for hydrogen atoms in microwave fields J. E. Bayfield, G. Casati, I. Guarneri and D. W. Sokol; 14. Inhibition of quantum transport due to 'scars' of unstable periodic orbits R. V. Jensen, M. M. Sanders, M. Saraceno and B. Sundaram; 15. Rubidium Rydberg atoms in strong fields G. Benson, G. Raithel and H. Walther; 16. Diamagnetic Rydberg atom: confrontation of calculated and observed spectra C.-H. Iu, G. R. Welch, M. M. Kash, D. Kleppner, D. Delande and J. C. Gay; 17. Semiclassical approximation for the quantum states of a hydrogen atom in a magnetic field near the ionization limit M. Y. Kuchiev and O. P. Sushkov; 18. The semiclassical helium atom D. Wintgen, K. Richter and G. Tanner; 19. Stretched helium: a model for quantum chaos

  6. Quantum Chaos

    NASA Astrophysics Data System (ADS)

    Casati, Giulio; Chirikov, Boris

    1995-04-01

    Preface; Acknowledgments; Introduction: 1. The legacy of chaos in quantum mechanics G. Casati and B. V. Chirikov; Part I. Classical Chaos and Quantum Localization: 2. Stochastic behaviour of a quantum pendulum under a periodic perturbation G. Casati, B. V. Chirikov, F. M. Izrailev and J. Ford; 3. Quantum dynamics of a nonintegrable system D. R. Grempel, R. E. Prange and S. E. Fishman; 4. Excitation of molecular rotation by periodic microwave pulses. A testing ground for Anderson localization R. Blümel, S. Fishman and U. Smilansky; 5. Localization of diffusive excitation in multi-level systems D. K. Shepelyansky; 6. Classical and quantum chaos for a kicked top F. Haake, M. Kus and R. Scharf; 7. Self-similarity in quantum dynamics L. E. Reichl and L. Haoming; 8. Time irreversibility of classically chaotic quantum dynamics K. Ikeda; 9. Effect of noise on time-dependent quantum chaos E. Ott, T. M. Antonsen Jr and J. D. Hanson; 10. Dynamical localization, dissipation and noise R. F. Graham; 11. Maximum entropy models and quantum transmission in disordered systems J.-L. Pichard and M. Sanquer; 12. Solid state 'atoms' in intense oscillating fields M. S. Sherwin; Part II. Atoms in Strong Fields: 13. Localization of classically chaotic diffusion for hydrogen atoms in microwave fields J. E. Bayfield, G. Casati, I. Guarneri and D. W. Sokol; 14. Inhibition of quantum transport due to 'scars' of unstable periodic orbits R. V. Jensen, M. M. Sanders, M. Saraceno and B. Sundaram; 15. Rubidium Rydberg atoms in strong fields G. Benson, G. Raithel and H. Walther; 16. Diamagnetic Rydberg atom: confrontation of calculated and observed spectra C.-H. Iu, G. R. Welch, M. M. Kash, D. Kleppner, D. Delande and J. C. Gay; 17. Semiclassical approximation for the quantum states of a hydrogen atom in a magnetic field near the ionization limit M. Y. Kuchiev and O. P. Sushkov; 18. The semiclassical helium atom D. Wintgen, K. Richter and G. Tanner; 19. Stretched helium: a model for quantum chaos

  7. Microwave analysis of MSM photodiodes for time-resolved measurements of RSFQ pulses

    NASA Astrophysics Data System (ADS)

    Badi, Siham; Febvre, Pascal

    2006-10-01

    This paper deals with the study of metal-semiconductor-metal (MSM) photodetectors used for time-resolved detection of low amplitude picosecond-range signals, such as rapid single flux quantum (RSFQ) pulses (Likharev and Semenov 1991 IEEE Trans. Appl. Supercond. 1 3-27) generated by superconductive electronic circuits. A typical 6 ps wide incoming RSFQ pulse of 200 µV amplitude has been used for the analysis. The photodetector detection behaviour has been studied in the microwave frequency range for different geometrical parameters in the OFF (no optical illumination) and ON modes. It is shown that, with properly chosen geometry, the photoswitches exhibit good transmission of RSFQ pulses in the ON mode while reasonably shorting them in the OFF mode.

  8. Minimal-excitation states for electron quantum optics using levitons

    NASA Astrophysics Data System (ADS)

    Dubois, J.; Jullien, T.; Portier, F.; Roche, P.; Cavanna, A.; Jin, Y.; Wegscheider, W.; Roulleau, P.; Glattli, D. C.

    2013-10-01

    The on-demand generation of pure quantum excitations is important for the operation of quantum systems, but it is particularly difficult for a system of fermions. This is because any perturbation affects all states below the Fermi energy, resulting in a complex superposition of particle and hole excitations. However, it was predicted nearly 20 years ago that a Lorentzian time-dependent potential with quantized flux generates a minimal excitation with only one particle and no hole. Here we report that such quasiparticles (hereafter termed levitons) can be generated on demand in a conductor by applying voltage pulses to a contact. Partitioning the excitations with an electronic beam splitter generates a current noise that we use to measure their number. Minimal-excitation states are observed for Lorentzian pulses, whereas for other pulse shapes there are significant contributions from holes. Further identification of levitons is provided in the energy domain with shot-noise spectroscopy, and in the time domain with electronic Hong-Ou-Mandel noise correlations. The latter, obtained by colliding synchronized levitons on a beam splitter, exemplifies the potential use of levitons for quantum information: using linear electron quantum optics in ballistic conductors, it is possible to imagine flying-qubit operation in which the Fermi statistics are exploited to entangle synchronized electrons emitted by distinct sources. Compared with electron sources based on quantum dots, the generation of levitons does not require delicate nanolithography, considerably simplifying the circuitry for scalability. Levitons are not limited to carrying a single charge, and so in a broader context n-particle levitons could find application in the study of full electron counting statistics. But they can also carry a fraction of charge if they are implemented in Luttinger liquids or in fractional quantum Hall edge channels; this allows the study of Abelian and non-Abelian quasiparticles in the

  9. Superconducting electronics: Prospects for digital and quantum computing

    NASA Astrophysics Data System (ADS)

    Herr, Andrea Marie

    Quantum computation has the potential to provide an efficient means of solving certain problems which are intractable on classical machines. Superconducting electronics may enable a solid state quantum computer of macroscopic dimensions. The first step is to demonstrate macroscopic quantum coherence in a single superconducting rf-SQUID qubit, manifest as the tunneling of magnetic flux in and out of the SQUID loop, or equivalently, the phase across the junction alternately increasing and decreasing by 2pi. This will likely require improvements in the current fabrication technology, as it will require submicron junctions with extremely low leakage current. We propose a scheme to experimentally demonstrate macroscopic quantum coherence in the rf-SQUID qubit by speeding up the time evolution of the system by momentarily suppressing the junction critical current through the application of a series of single flux quantum (SFQ) pulses. The precise timing of the perturbing pulses and the subsequent measurement of the qubit state would be performed using rapid single flux quantum (RSFQ) circuitry. Conventional digital electronics based on the single flux quantum offers very low power dissipation and high operating frequency. These same features, however, make timing of clock and data signals difficult. Circuits with recurrent data paths, such as the circular shift register (CSR) have the most stringent timing requirements. A 64-bit CSR composed of approximately 425 Josephson junctions was designed and successfully demonstrated. The CSR has an area of 0.8 mm2 and consumes approximately 80 muW of power. The circuit showed correct operation at low speed with a critical margin of +/-7.5%, and operated correctly at frequencies up to 18 GHz. The bit-error rate (BER) of the 64-bit CSR, i.e. the probability that an error in circuit operation will occur during any single circulation of the data through all 64 register stages, was measured as a function of clock frequency, and the

  10. Pulse Propagation in Phaseonium

    NASA Astrophysics Data System (ADS)

    Rahman, Ashiqur; Eberly, J. H.

    1996-05-01

    Phaseonium [1] is a medium where the quantum atomic phase is held fixed for long times compared with various relaxation processes. In inhomogeneously broadened two-level phaseonium, we have found a new area theorem (similar to self-induced transparency [2]) for pulse propagation, where pulses of arbitrary area can be stable instead of 2π area. We will also report results for inhomogeneously broadened three-level phaseonium. Research partially supported by NSF grant PHY94-08733. [1] M.O. Scully, Phys. Rev. Lett. 55, 2802 (1985), also Quant. Opt. 6, 203 (1994). [2] S. L. McCall and E. L. Hahn, Phys. Rev. 183, 457 (1969).

  11. High Power Picosecond Laser Pulse Recirculation

    SciTech Connect

    Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P

    2010-04-12

    We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering based light sources. We demonstrate up to 36x average power enhancement of frequency doubled sub-millijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

  12. APPLICATIONS OF LASERS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Laser system based on a commercial microwave oscillator with time compression of a microwave pump pulse

    NASA Astrophysics Data System (ADS)

    Arteev, M. S.; Vaulin, V. A.; Slinko, V. N.; Chumerin, P. Yu; Yushkov, Yu G.

    1992-06-01

    An analysis is made of the possibility of using a commercial microsecond microwave oscillator, supplemented by a device for time compression of microwave pulses, in pumping of industrial lasers with a high efficiency of conversion of the pump source energy into laser radiation. The results are reported of preliminary experiments on the commissioning of an excimer XeCl laser.

  13. Quantum phase slip noise

    NASA Astrophysics Data System (ADS)

    Semenov, Andrew G.; Zaikin, Andrei D.

    2016-07-01

    Quantum phase slips (QPSs) generate voltage fluctuations in superconducting nanowires. Employing the Keldysh technique and making use of the phase-charge duality arguments, we develop a theory of QPS-induced voltage noise in such nanowires. We demonstrate that quantum tunneling of the magnetic flux quanta across the wire yields quantum shot noise which obeys Poisson statistics and is characterized by a power-law dependence of its spectrum SΩ on the external bias. In long wires, SΩ decreases with increasing frequency Ω and vanishes beyond a threshold value of Ω at T →0 . The quantum coherent nature of QPS noise yields nonmonotonous dependence of SΩ on T at small Ω .

  14. Pulse Oximetry

    MedlinePlus

    ... www.thoracic.org amount of gases (oxygen and carbon dioxide) that are in your blood. To get an ... Also, a pulse oximeter does not measure your carbon dioxide level. How accurate is the pulse oximeter? The ...

  15. Comparison of the high temperature heat flux sensor to traditional heat flux gages under high heat flux conditions.

    SciTech Connect

    Blanchat, Thomas K.; Hanks, Charles R.

    2013-04-01

    Four types of heat flux gages (Gardon, Schmidt-Boelter, Directional Flame Temperature, and High Temperature Heat Flux Sensor) were assessed and compared under flux conditions ranging between 100-1000 kW/m2, such as those seen in hydrocarbon fire or propellant fire conditions. Short duration step and pulse boundary conditions were imposed using a six-panel cylindrical array of high-temperature tungsten lamps. Overall, agreement between all gages was acceptable for the pulse tests and also for the step tests. However, repeated tests with the HTHFS with relatively long durations at temperatures approaching 1000%C2%B0C showed a substantial decrease (10-25%) in heat flux subsequent to the initial test, likely due to the mounting technique. New HTHFS gages have been ordered to allow additional tests to determine the cause of the flux reduction.

  16. SQUID detected NMR and NQR. Superconducting Quantum Interference Device.

    PubMed

    Augustine, M P; TonThat, D M; Clarke, J

    1998-03-01

    The dc Superconducting QUantum Interference Device (SQUID) is a sensitive detector of magnetic flux, with a typical flux noise of the order 1 muphi0 Hz(-1/2) at liquid helium temperatures. Here phi0 = h/2e is the flux quantum. In our NMR or NQR spectrometer, a niobium wire coil wrapped around the sample is coupled to a thin film superconducting coil deposited on the SQUID to form a flux transformer. With this untuned input circuit the SQUID measures the flux, rather than the rate of change of flux, and thus retains its high sensitivity down to arbitrarily low frequencies. This feature is exploited in a cw spectrometer that monitors the change in the static magnetization of a sample induced by radio frequency irradiation. Examples of this technique are the detection of NQR in 27Al in sapphire and 11B in boron nitride, and a level crossing technique to enhance the signal of 14N in peptides. Research is now focused on a SQUID-based spectrometer for pulsed NQR and NMR, which has a bandwidth of 0-5 MHz. This spectrometer is used with spin-echo techniques to measure the NQR longitudinal and transverse relaxation times of 14N in NH4ClO4, 63+/-6 ms and 22+/-2 ms, respectively. With the aid of two-frequency pulses to excite the 359 kHz and 714 kHz resonances in ruby simultaneously, it is possible to obtain a two-dimensional NQR spectrum. As a third example, the pulsed spectrometer is used to study NMR spectrum of 129Xe after polariza-tion with optically pumped Rb. The NMR line can be detected at frequencies as low as 200 Hz. At fields below about 2 mT the longitudinal relaxation time saturates at about 2000 s. Two recent experiments in other laboratories have extended these pulsed NMR techniques to higher temperatures and smaller samples. In the first, images were obtained of mineral oil floating on water at room temperature. In the second, a SQUID configured as a thin film gradiometer was used to detect NMR in a 50 microm particle of 195Pt at 6 mT and 4.2 K. PMID:9650797

  17. Infrared spectroscopic analysis of human interstitial fluid in vitro and in vivo using FT-IR spectroscopy and pulsed quantum cascade lasers (QCL): Establishing a new approach to non invasive glucose measurement

    NASA Astrophysics Data System (ADS)

    Pleitez, Miguel; von Lilienfeld-Toal, Hermann; Mäntele, Werner

    2012-01-01

    Interstitial fluid, i.e. the liquid present in the outermost layer of living cells of the skin between the Stratum corneum and the Stratum spinosum, was analyzed by Fourier transform infrared spectroscopy and by infrared spectroscopy using pulsed quantum cascade infrared lasers with photoacoustic detection. IR spectra of simulated interstitial fluid samples and of real samples from volunteers in the 850-1800 cm -1 range revealed that the major components of interstitial fluid are albumin and glucose within the physiological range, with only traces of sodium lactate if at all. The IR absorbance of glucose in interstitial fluid in vivo was probed in healthy volunteers using a setup with quantum cascade lasers and photoacoustic detection previously described [11]. A variation of blood glucose between approx. 80 mg/dl and 250 mg/dl in the volunteers was obtained using the standard oral glucose tolerance test (OGT). At two IR wavelengths, 1054 cm -1 and 1084 cm -1, a reasonable correlation between the photoacoustic signal from the skin and the blood glucose value as determined by conventional glucose test sticks using blood from the finger tip was obtained. The infrared photoacoustic glucose signal (PAGS) may serve as the key for a non-invasive glucose measurement, since the glucose content in interstitial fluid closely follows blood glucose in the time course and in the level (a delay of some minutes and a level of approx. 80-90% of the glucose level in blood). Interstitial fluid is present in skin layers at a depth of only 15-50 μm and is thus within the reach of mid-IR energy in an absorbance measurement. A non-invasive glucose measurement for diabetes patients based on mid-infrared quantum cascade lasers and photoacoustic detection could replace the conventional measurement using enzymatic test stripes and a drop of blood from the finger tip, thus reducing pain and being a cost-efficient alternative for millions of diabetes patients.

  18. Investigation of magnetoabsorption at different temperatures in HgTe/CdHgTe quantum-well heterostructures in pulsed magnetic fields

    SciTech Connect

    Platonov, V. V.; Kudasov, Yu. B.; Makarov, I. V.; Maslov, D. A.; Surdin, O. M.; Zholudev, M. S.; Ikonnikov, A. V.; Gavrilenko, V. I.; Mikhailov, N. N.; Dvoretsky, S. A.

    2015-12-15

    The magnetoabsorption in magnetic fields as high as 40 T is investigated at T > 77 K in HgTe/CdHgTe quantum-well heterostructures (d{sub QW} ≈ 8 nm). The spectra reveal two lines associated both with intraband transition from the lower Landau level in the conduction band and with interband transition. It is shown that the band structure in these systems changes from inverted to normal with increasing temperature.

  19. The dynamics of compact laser pulses

    NASA Astrophysics Data System (ADS)

    Goto, S.; Tucker, R. W.; Walton, T. J.

    2016-07-01

    We discuss the use of a class of exact finite energy solutions to the vacuum source-free Maxwell equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged point particles. These compact solutions are classified in terms of their chiral content and their influence on particular charge configurations in space. The results of such classical interactions motivate a phenomenological quantum description of a propagating laser pulse in a medium in terms of an effective quantum Hamiltonian.

  20. Quantum Computation and Quantum Information

    NASA Astrophysics Data System (ADS)

    Nielsen, Michael A.; Chuang, Isaac L.

    2010-12-01

    Part I. Fundamental Concepts: 1. Introduction and overview; 2. Introduction to quantum mechanics; 3. Introduction to computer science; Part II. Quantum Computation: 4. Quantum circuits; 5. The quantum Fourier transform and its application; 6. Quantum search algorithms; 7. Quantum computers: physical realization; Part III. Quantum Information: 8. Quantum noise and quantum operations; 9. Distance measures for quantum information; 10. Quantum error-correction; 11. Entropy and information; 12. Quantum information theory; Appendices; References; Index.

  1. PULSE GENERATOR

    DOEpatents

    Roeschke, C.W.

    1957-09-24

    An improvement in pulse generators is described by which there are produced pulses of a duration from about 1 to 10 microseconds with a truly flat top and extremely rapid rise and fall. The pulses are produced by triggering from a separate input or by modifying the current to operate as a free-running pulse generator. In its broad aspect, the disclosed pulse generator comprises a first tube with an anode capacitor and grid circuit which controls the firing; a second tube series connected in the cathode circuit of the first tube such that discharge of the first tube places a voltage across it as the leading edge of the desired pulse; and an integrator circuit from the plate across the grid of the second tube to control the discharge time of the second tube, determining the pulse length.

  2. Temporal interferences driven by a single-cycle terahertz pulse in the photodetachment dynamics of negative ions

    NASA Astrophysics Data System (ADS)

    Yang, B. C.; Robicheaux, F.

    2015-12-01

    We present theory and calculations of a real-time-domain interferometry for the photodetachment dynamics of negative ions in the presence of a single-cycle terahertz pulse. The photoelectron can follow two or more classical trajectories to arrive at a detector simultaneously allowing the electron waves to interfere quantum mechanically. Both the in-phase and antiphase oscillations can be observed in the photoelectron interferences from negative hydrogen and fluorine ions depending on the pulse strength and the observing angle. Especially, a temporal-caustic bifurcation is observed when the detection angle is not in line with the pulse polarization direction. Similar interferences and bifurcations are also expected in the angle-resolved energy spectrum, as a result of its approximate equivalence with the time-dependent electron flux at large distances.

  3. Reconnecting Flux Ropes

    NASA Astrophysics Data System (ADS)

    Gekelman, Walter; van Compernolle, Bart

    2012-10-01

    Magnetic flux ropes are due to helical currents and form a dense carpet of arches on the surface of the sun. Occasionally one tears loose as a coronal mass ejection and its rope structure is detected by satellites close to the earth. Current sheets can tear into filaments and these are nothing other than flux ropes. Ropes are not static, they exert mutual JxB forces causing them to twist about each other and merge. Kink instabilities cause them to violently smash into each other and reconnect at the point of contact. We report on experiments done in the large plasma device (LAPD) at UCLA (L=17m,dia=60cm,0.3<=B0z<=2.5kG,n˜2x10^12cm-3)on three dimensional flux ropes. Two, three or more magnetic flux ropes are generated from initially adjacent pulsed current channels in a background magnetized plasma. The currents and magnetic fields form exotic shapes with no ignorable direction and no magnetic nulls. Volumetric space-time data show multiple reconnection sites with time-dependent locations. The concept of a quasi-separatrix layer (QSL), a tool to understand 3D reconnection without null points. In our experiment the QSL is a narrow ribbon-like region(s) that twists between field lines. Within the QSL(s) field lines that start close to one another rapidly diverge as they pass through one or more reconnection regions. When the field lines are tracked they are observed to slip along the QSL when reconnection occurs. The Heating and other co-existing waves will be presented.

  4. SQUID With Integral Flux Concentrator

    NASA Technical Reports Server (NTRS)

    Peters, Palmer N.; Sisk, Robert C.

    1989-01-01

    In improved superconducting quantum interference device (SQUID), change in size and shape of superconducting ring improves coupling to external signal coil and eases coil-positioning tolerances. More rugged and easier to manufacture than conventional SQUID's with comparable electrical characteristics. Thin-film superconducting flux concentrator utilizes Meissner effect to deflect magnetic field of signal coil into central hole of SQUID. Used in magnetometers, ammeters, analog-to-digital converters, and related electronic applications in which high signal-to-noise ratios required.

  5. Quantum gates by qubit frequency modulation in circuit QED

    NASA Astrophysics Data System (ADS)

    Beaudoin, Felix; da Silva, Marcus P.; Johnson, Blake R.; Ohki, Thomas A.; Dutton, Zachary; Blais, Alexandre

    2012-02-01

    Several types of two-qubit gates have been realized experimentally in circuit QED. These are based, for example, on tuning the pair of qubits in resonance with each other [Majer, Nature 449, 443-447 (2007)] or on a microwave pulse on one qubit at the transition frequency of a second qubit [Chow, Phys. Rev. Lett. 107, 080502 (2011)]. Another realization is based on a sequence of blue-sideband transitions generated by microwave pulses [Leek, Phys. Rev. B 79, 180511(R) (2009)]. Here, we propose a different approach relying on oscillations of the qubit frequency using a flux-bias line. We explain how frequency modulation leads to tunable qubit-resonator and qubit-qubit interactions. We also show how this form of quantum control leads to faster (first-order) sideband transitions and consider applications to two-qubit gates.

  6. Low-frequency self-pulsing in single-section quantum-dot laser diodes and its relation to optothermal pulsations

    SciTech Connect

    Tierno, A.; Radwell, N.; Ackemann, T.

    2011-10-15

    Self-sustained pulsations in the output of an InAs quantum dot laser diode in the MHz range are reported. The characteristics (shape, range, and frequency) are presented for the free-running laser and when optical feedback in the Littrow configuration is applied. Bistability in the light-current characteristics is observed for operating wavelengths smaller than the gain peak, but it is not present for wavelengths above the gain peak and for the free-running laser, except at elevated temperatures. The temporal evolution of the envelopes of the optical spectra is very different for operation below, around, and above the gain peak, which might be related to a change of phase-amplitude coupling across the gain maximum, in agreement with the expectation for a two-level system. The time scale and the bifurcation scenario, supported by an initial blueshift of the emission wavelength of each longitudinal mode in time-resolved optical spectra, suggests that these are optothermal pulsations similar to those reported in quantum well amplifiers [Phys. Rev. E 68, 036209 (2003)]. The mechanism of pulsation seems to be a destabilization of bistable states (due to saturable absorption in the beam wings) by a slow thermal change in the waveguiding properties.

  7. Pulse stretcher

    DOEpatents

    Horton, J.A.

    1994-05-03

    Apparatus for increasing the length of a laser pulse to reduce its peak power without substantial loss in the average power of the pulse is disclosed. The apparatus uses a White cell having a plurality of optical delay paths of successively increasing number of passes between the field mirror and the objective mirrors. A pulse from a laser travels through a multi-leg reflective path between a beam splitter and a totally reflective mirror to the laser output. The laser pulse is also simultaneously injected through the beam splitter to the input mirrors of the optical delay paths. The pulses from the output mirrors of the optical delay paths go simultaneously to the laser output and to the input mirrors of the longer optical delay paths. The beam splitter is 50% reflective and 50% transmissive to provide equal attenuation of all of the pulses at the laser output. 6 figures.

  8. STIRAP with XFEL pulses

    NASA Astrophysics Data System (ADS)

    Picon, Antonio; Southworth, Stephen

    2015-05-01

    The development of the laser in the optical-IR regime stimulated completely new schemes for controlling quantum systems by resorting to the coherence of the light-matter interaction. Along this line, it is interesting to explore these schemes or new ones in the x-ray regime, especially with the advent of x-ray free-electron lasers (XFELs) which deliver spatio-temporal coherent pulses in the femtosecond timescale. The new factor in the x-ray regime with respect to the optical regime is the unavoidable creation and ultrafast decay of core-excited states driven by strong electron correlations that one needs to consider. Hence, X-Ray Quantum Optics opens an interesting field in order to explore strongly correlated systems driven by x-ray pulses, and definitely it will play a crucial role in the development of characterization methods for x-ray pulses at XFELs. Here, we propose a theoretical scheme for STIRAP (Stimulated Raman Adiabatic Passage) in Ne gas for the soft x-ray regime. Experimental feasibility will be discussed. This work is funded by the Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, under Contract No. DE-AC02-06CH11357.

  9. Pulsed power

    NASA Astrophysics Data System (ADS)

    Stone, David H.

    Pulsed power systems are critical elements for such prospective weapons technologies as high-power microwaves, electrothermal and electromagnetic projectile launchers, neutral particle beams, space-based FELs, ground-based lasers, and charged particle beams. Pulsed power will also be essential for the development of nonweapon military systems such as lidars and ultrawideband radars, and could serve as the bases for nuclear weapon effect simulators. The pulsed power generation requirements for each of these systems is considered.

  10. Entanglement generation and quantum information transfer between spatially-separated qubits in different cavities

    NASA Astrophysics Data System (ADS)

    Yang, Chui-Ping; Su, Qi-Ping; Nori, Franco

    2013-11-01

    The generation and control of quantum states of spatially-separated qubits distributed in different cavities constitute fundamental tasks in cavity quantum electrodynamics (QED). An interesting question in this context is how to prepare entanglement and realize quantum information transfer between qubits located at different cavities, which are important in large-scale quantum information processing. In this paper, we consider a physical system consisting of two cavities and three qubits. Two of the qubits are placed in two different cavities while the remaining one acts as a coupler, which is used to connect the two cavities. We propose an approach for generating quantum entanglement and implementing quantum information transfer between the two spatially-separated inter-cavity qubits. The quantum operations involved in this proposal are performed by a virtual photon process; thus the cavity decay is greatly suppressed during operations. In addition, to complete these tasks, only one coupler qubit and one operation step are needed. Moreover, there is no need to apply classical pulses, so that the engineering complexity is much reduced and the operation procedure is greatly simplified. Finally, our numerical results illustrate that high-fidelity implementation of this proposal using superconducting phase qubits and one-dimensional transmission line resonators is feasible for current circuit QED implementations. This proposal can also be applied to other types of superconducting qubits, including flux and charge qubits.

  11. Pulse Voltammetry

    NASA Astrophysics Data System (ADS)

    Stojek, Zbigniew

    The idea of imposing potential pulses and measuring the currents at the end of each pulse was proposed by Barker in a little-known journal as early as in 1958 [1]. However, the first reliable trouble-free and affordable polarographs offering voltammetric pulse techniques appeared on the market only in the 1970s. This delay was due to some limitations on the electronic side. In the 1990s, again substantial progress in electrochemical pulse instrumentation took place. This was related to the introduction of microprocessors, computers, and advanced software.

  12. Rotating flux compressor for energy conversion

    SciTech Connect

    Chowdhuri, P.; Linton, T.W.; Phillips, J.A.

    1983-01-01

    The rotating flux compressor (RFC) converts rotational kinetic energy into an electrical output pulse which would have higher energy than the electrical energy initially stored in the compressor. An RFC has been designed in which wedge-shaped rotor blades pass through the air gaps between successive turns of a solenoid, the stator. Magnetic flux is generated by pulsing the stator solenoids when the inductance is a maximum, i.e., when the flux fills the stator-solenoid volume. Connecting the solenoid across a load conserves the flux which is compressed within the small volume surrounding the stator periphery when the rotor blades cut into the free space between the stator plates, creating a minimum-inductance condition. The unique features of this design are: (1) no electrical connections (brushes) to the rotor; (2) no conventional windings; and (3) no maintenance. The device has been tested up to 5000 rpm of rotor speed.

  13. PULSE AMPLIFIER

    DOEpatents

    Johnstone, C.W.

    1958-06-17

    The improvement of pulse amplifiers used with scintillation detectors is described. The pulse amplifier circuit has the advantage of reducing the harmful effects of overloading cause by large signal inputs. In general the pulse amplifier circuit comprises two amplifier tubes with the input pulses applied to one amplifier grid and coupled to the second amplifier tube through a common cathode load. The output of the second amplifier is coupled from the plate circuit to a cathode follower tube grid and a diode tube in connected from grid to cathode of the cathode follower tube. Degenerative feedback is provided in the second amplifier by coupling a signal from the cathode follower cathode to the second amplifier grid. The circuit proqides moderate gain stability, and overload protection for subsequent pulse circuits.

  14. Micro pulse laser radar

    NASA Technical Reports Server (NTRS)

    Spinhirne, James D. (Inventor)

    1993-01-01

    An eye safe, compact, solid state lidar for profiling atmospheric cloud and aerosol scattering is disclosed. The transmitter of the micro pulse lidar is a diode pumped micro-J pulse energy, high repetition rate Nd:YLF laser. Eye safety is obtained through beam expansion. The receiver employs a photon counting solid state Geiger mode avalanche photodiode detector. Data acquisition is by a single card multichannel scaler. Daytime background induced quantum noise is controlled by a narrow receiver field-of-view and a narrow bandwidth temperature controlled interference filter. Dynamic range of the signal is limited to optical geometric signal compression. Signal simulations and initial atmospheric measurements indicate that micropulse lider systems are capable of detecting and profiling all significant cloud and aerosol scattering through the troposphere and into the stratosphere. The intended applications are scientific studies and environmental monitoring which require full time, unattended measurements of the cloud and aerosol height structure.

  15. Phase and intensity characterization of femtosecond pulses from a chirped-pulse amplifier by frequency-resolved optical gating

    SciTech Connect

    Kohler, B.; Yakovlev, V.V.; Wilson, K.R.; Squier, J.; DeLong, K.W.; Trebino, R.

    1995-03-01

    Frequency-resolved optical gating (FROG) measurements were made to characterize pulses from a Ti:sapphire chirped-pulse amplified laser system. By characterizing both the pulse intensity and the phase, the FROG data provided the first direct observation to our knowledge of residual phase distortion in a chirped-pulse amplifier. The FROG technique was also used to measure the regenerative amplifier dispersion and to characterize an amplitude-shaped pulse. The data provide an experimental demonstration of the value of FROG for characterizing complex pulses, including tailored femtosecond pulses for quantum control.

  16. A highly sensitive differential pulse anodic stripping voltammetry for determination of 17β-estradiol (E2) using CdSe quantum dots based on indirect competitive immunoassay.

    PubMed

    Chaisuwan, Nuanapa; Xu, He; Wu, Genying; Liu, Jianshe

    2013-08-15

    In this study a new and fast procedure was developed to determine trace 17β-estradiol (E2) concentrations using CdSe quantum dots (QDs) conjugation with bovine serum albumin (BSA)-E2. To increase the high efficiency of the method, the immunoassay design was restricted to an indirect competitive format. The E2 antigen and bioconjugate were incubated in a microtiter plate with an anti-E2 antibody and competition for antibody binding sites was established. The in situ bismuth-coated carbon electrodes were used for detecting the cadmium ions (Cd(2+)) released during the acid dissolution step. After optimization, the well-defined sharp anodic stripping voltammograms curves of the E2 concentration ranging from 50 to 1000 pg/mL was recorded, and the lowest detection limit was 50 pg/mL with 6% reproducibility and 7% repeatability. Finally, the assay was applied to tap water and wastewater samples. The detection limits were 52.56 ± 0.125 pg/mL for tap water and 51.42 ± 0.453 pg/mL for wastewater. These results show that the assay exhibited sensitive analytical performance in E2 detection with high sensitivity and accuracy with satisfactory results. PMID:23542084

  17. Attosecond quantum stroboscope.

    PubMed

    Paulus, Gerhard G; Stania, Gernot

    2009-04-14

    Electron disco: A "quantum stroboscope" for capturing the electron motion on a subfemtosecond timescale for a particular class of problems is highlighted. The picture shows a diffraction pattern caused by wave packets obtained by synchronizing attosecond UV pulses to a near-IR field and ionizing rare-gas atoms. PMID:19294685

  18. Ultrashort pulsed neutron source.

    PubMed

    Pomerantz, I; McCary, E; Meadows, A R; Arefiev, A; Bernstein, A C; Chester, C; Cortez, J; Donovan, M E; Dyer, G; Gaul, E W; Hamilton, D; Kuk, D; Lestrade, A C; Wang, C; Ditmire, T; Hegelich, B M

    2014-10-31

    We report on a novel compact laser-driven neutron source with an unprecedented short pulse duration (<50  ps) and high peak flux (>10(18)  n/cm(2)/s), an order of magnitude higher than any existing source. In our experiments, high-energy electron jets are generated from thin (<3  μm) plastic targets irradiated by a petawatt laser. These intense electron beams are employed to generate neutrons from a metal converter. Our method opens venues for enhancing neutron radiography contrast and for creating astrophysical conditions of heavy element synthesis in the laboratory. PMID:25396373

  19. Ultrashort Pulsed Neutron Source

    NASA Astrophysics Data System (ADS)

    Pomerantz, I.; McCary, E.; Meadows, A. R.; Arefiev, A.; Bernstein, A. C.; Chester, C.; Cortez, J.; Donovan, M. E.; Dyer, G.; Gaul, E. W.; Hamilton, D.; Kuk, D.; Lestrade, A. C.; Wang, C.; Ditmire, T.; Hegelich, B. M.

    2014-10-01

    We report on a novel compact laser-driven neutron source with an unprecedented short pulse duration (<50 ps ) and high peak flux (>1018 n /cm2/s ), an order of magnitude higher than any existing source. In our experiments, high-energy electron jets are generated from thin (<3 μ m ) plastic targets irradiated by a petawatt laser. These intense electron beams are employed to generate neutrons from a metal converter. Our method opens venues for enhancing neutron radiography contrast and for creating astrophysical conditions of heavy element synthesis in the laboratory.

  20. Multiple quantum coherence spectroscopy.

    PubMed

    Mathew, Nathan A; Yurs, Lena A; Block, Stephen B; Pakoulev, Andrei V; Kornau, Kathryn M; Wright, John C

    2009-08-20

    Multiple quantum coherences provide a powerful approach for studies of complex systems because increasing the number of quantum states in a quantum mechanical superposition state increases the selectivity of a spectroscopic measurement. We show that frequency domain multiple quantum coherence multidimensional spectroscopy can create these superposition states using different frequency excitation pulses. The superposition state is created using two excitation frequencies to excite the symmetric and asymmetric stretch modes in a rhodium dicarbonyl chelate and the dynamic Stark effect to climb the vibrational ladders involving different overtone and combination band states. A monochromator resolves the free induction decay of different coherences comprising the superposition state. The three spectral dimensions provide the selectivity required to observe 19 different spectral features associated with fully coherent nonlinear processes involving up to 11 interactions with the excitation fields. The different features act as spectroscopic probes of the diagonal and off-diagonal parts of the molecular potential energy hypersurface. This approach can be considered as a coherent pump-probe spectroscopy where the pump is a series of excitation pulses that prepares a multiple quantum coherence and the probe is another series of pulses that creates the output coherence. PMID:19507812

  1. Pulse Voltammetry.

    ERIC Educational Resources Information Center

    Osteryoung, Janet

    1983-01-01

    Discusses the nature of pulse voltammetry, indicating that its widespread use arises from good sensitivity and detection limits and from ease of application and low cost. Provides analytical and mechanistic applications of the procedure. (JN)

  2. Photo-induced conductance fluctuations in mesoscopic Ge/Si systems with quantum dots

    SciTech Connect

    Stepina, N. P.; Dvurechenskii, A. V.; Nikiforov, A. I.; Moers, J.; Gruetzmacher, D.

    2014-08-20

    We study the evolution of electron transport in strongly localized mesoscopic system with quantum dots under small photon flux. Exploring devices with narrow transport channels lead to the observation of giant fluctuations of the photoconductance, which is attributed to the strong dependence of hopping current on the filling of dots by holes. In our experiments, single-photon mode operation is indicated by the linear dependence of the frequency of photo-induced fluctuations on the light intensity and the step-like response of conductance on the pulse excitation. The effect of the light wavelength, measurement temperature, size of the conductive channel on the device efficiency are considered.

  3. Pulse stretcher

    DOEpatents

    Horton, James A.

    1994-01-01

    Apparatus (20) for increasing the length of a laser pulse to reduce its peak power without substantial loss in the average power of the pulse. The apparatus (20) uses a White cell (10) having a plurality of optical delay paths (18a-18d) of successively increasing number of passes between the field mirror (13) and the objective mirrors (11 and 12). A pulse (26) from a laser (27) travels through a multi-leg reflective path (28) between a beam splitter (21) and a totally reflective mirror (24) to the laser output (37). The laser pulse (26) is also simultaneously injected through the beam splitter (21) to the input mirrors (14a-14d) of the optical delay paths (18a-18d). The pulses from the output mirrors (16a-16d) of the optical delay paths (18a-18d) go simultaneously to the laser output (37) and to the input mirrors ( 14b-14d) of the longer optical delay paths. The beam splitter (21) is 50% reflective and 50% transmissive to provide equal attenuation of all of the pulses at the laser output (37).

  4. Neutron flux profile monitor for use in a fission reactor

    DOEpatents

    Kopp, Manfred K.; Valentine, Kenneth H.

    1983-01-01

    A neutron flux monitor is provided which consists of a plurality of fission counters arranged as spaced-apart point detectors along a delay line. As a fission event occurs in any one of the counters, two delayed current pulses are generated at the output of the delay line. The time separation of the pulses identifies the counter in which the particular fission event occured. Neutron flux profiles of reactor cores can be more accurately measured as a result.

  5. Molecular wave packet interferometry and quantum entanglement

    NASA Astrophysics Data System (ADS)

    Martínez-Galicia, Ricardo; Romero-Rochín, Víctor

    2005-03-01

    We study wave packet interferometry (WPI) considering the laser pulse fields both classical and quantum mechanically. WPI occurs in a molecule after subjecting it to the interaction with a sequence of phase-locked ultrashort laser pulses. Typically, the measured quantity is the fluorescence of the molecule from an excited electronic state. This signal has imprinted the interference of the vibrational wave packets prepared by the different laser pulses of the sequence. The consideration of the pulses as quantum entities in the analysis allows us to study the entanglement of the laser pulse states with the molecular states. With a simple model for the molecular system, plus several justified approximations, we solve for the fully quantum mechanical molecule-electromagnetic field state. We then study the reduced density matrices of the molecule and the laser pulses separately. We calculate measurable corrections to the case where the fields are treated classically.

  6. Pulsed Operation of an Ion Accelerator

    NASA Technical Reports Server (NTRS)

    Wirz, Richard; Gamero-Castano, Manuel; Goebel, Dan

    2009-01-01

    Electronic circuitry has been devised to enable operation of an ion accelerator in either a continuous mode or a highpeak power, low-average-power pulsed mode. In the original intended application, the ion accelerator would be used as a spacecraft thruster and the pulse mode would serve to generate small increments of impulse for precise control of trajectories and attitude. The present electronic drive circuitry generates the extraction voltage in pulses. Pulse-width modulation can affect rapid, fine control of time-averaged impulse or ion flux down to a minimum level much lower than that achievable in continuous operation.

  7. Experimental Satellite Quantum Communications

    NASA Astrophysics Data System (ADS)

    Vallone, Giuseppe; Bacco, Davide; Dequal, Daniele; Gaiarin, Simone; Luceri, Vincenza; Bianco, Giuseppe; Villoresi, Paolo

    2015-07-01

    Quantum communication (QC), namely, the faithful transmission of generic quantum states, is a key ingredient of quantum information science. Here we demonstrate QC with polarization encoding from space to ground by exploiting satellite corner cube retroreflectors as quantum transmitters in orbit and the Matera Laser Ranging Observatory of the Italian Space Agency in Matera, Italy, as a quantum receiver. The quantum bit error ratio (QBER) has been kept steadily low to a level suitable for several quantum information protocols, as the violation of Bell inequalities or quantum key distribution (QKD). Indeed, by taking data from different satellites, we demonstrate an average value of QBER =4.6 % for a total link duration of 85 s. The mean photon number per pulse μsat leaving the satellites was estimated to be of the order of one. In addition, we propose a fully operational satellite QKD system by exploiting our communication scheme with orbiting retroreflectors equipped with a modulator, a very compact payload. Our scheme paves the way toward the implementation of a QC worldwide network leveraging existing receivers.

  8. Experimental Satellite Quantum Communications.

    PubMed

    Vallone, Giuseppe; Bacco, Davide; Dequal, Daniele; Gaiarin, Simone; Luceri, Vincenza; Bianco, Giuseppe; Villoresi, Paolo

    2015-07-24

    Quantum communication (QC), namely, the faithful transmission of generic quantum states, is a key ingredient of quantum information science. Here we demonstrate QC with polarization encoding from space to ground by exploiting satellite corner cube retroreflectors as quantum transmitters in orbit and the Matera Laser Ranging Observatory of the Italian Space Agency in Matera, Italy, as a quantum receiver. The quantum bit error ratio (QBER) has been kept steadily low to a level suitable for several quantum information protocols, as the violation of Bell inequalities or quantum key distribution (QKD). Indeed, by taking data from different satellites, we demonstrate an average value of QBER=4.6% for a total link duration of 85 s. The mean photon number per pulse μ_{sat} leaving the satellites was estimated to be of the order of one. In addition, we propose a fully operational satellite QKD system by exploiting our communication scheme with orbiting retroreflectors equipped with a modulator, a very compact payload. Our scheme paves the way toward the implementation of a QC worldwide network leveraging existing receivers. PMID:26252672

  9. Fast flux locked loop

    DOEpatents

    Ganther, Jr., Kenneth R.; Snapp, Lowell D.

    2002-09-10

    A flux locked loop for providing an electrical feedback signal, the flux locked loop employing radio-frequency components and technology to extend the flux modulation frequency and tracking loop bandwidth. The flux locked loop of the present invention has particularly useful application in read-out electronics for DC SQUID magnetic measurement systems, in which case the electrical signal output by the flux locked loop represents an unknown magnetic flux applied to the DC SQUID.

  10. Paramagnetic-Salt Thermometer With Flux Pump And SQUID's

    NASA Technical Reports Server (NTRS)

    Strayer, Donald M.; Israelsson, Ulf E.

    1993-01-01

    Paramagnetic-salt low-temperature thermometer incorporates improved superconducting magnetic-flux pump, multiple superconducting quantum interference devices as magnetometers, and feedback stabilization of magnetic flux. Requires much smaller initial magnetizing currents and provides improved temperature resolution via suppression of drift in magnetic induction.

  11. A Stringy Test of Flux-Induced Isometry Gauging

    SciTech Connect

    Kashani-Poor, Amir-Kian; Tomasiello, Alessandro; /Stanford U., ITP

    2005-06-29

    Supergravity analysis suggests that the effect of fluxes in string theory compactifications is to gauge isometries of the scalar manifold. However, isometries are generically broken by brane instanton effects. Here we demonstrate how fluxes protect exactly those isometries from quantum corrections which are gauged according to the classical supergravity analysis. We also argue that all other isometries are generically broken.

  12. Navigation between quantum states by quantum mirrors

    NASA Astrophysics Data System (ADS)

    Ivanov, P. A.; Torosov, B. T.; Vitanov, N. V.

    2007-01-01

    We introduce a technique that allows one to connect any two arbitrary (pure or mixed) superposition states of an N -state quantum system. The proposed solution to this inverse quantum mechanical problem is analytical, exact, and very compact. The technique uses standard and generalized quantum Householder reflections (QHRs), which require external pulses of precise areas and frequencies. We show that any two pure states can be linked by just a single generalized QHR. The transfer between any two mixed states with the same dynamic invariants (e.g., the same density matrix eigenvalues) requires in general N QHRs. Moreover, we propose recipes for synthesis of arbitrary preselected mixed states using a combination of QHRs and incoherent processes (pure dephasing or spontaneous emission).

  13. STATISTICAL STUDIES OF GIANT PULSE EMISSION FROM THE CRAB PULSAR

    SciTech Connect

    Majid, Walid A.; Naudet, Charles J.; Lowe, Stephen T.; Kuiper, Thomas B. H.

    2011-11-01

    We have observed the Crab pulsar with the Deep Space Network Goldstone 70 m antenna at 1664 MHz during three observing epochs for a total of 4 hr. Our data analysis has detected more than 2500 giant pulses, with flux densities ranging from 0.1 kJy to 150 kJy and pulse widths from 125 ns (limited by our bandwidth) to as long as 100 {mu}s, with median power amplitudes and widths of 1 kJy and 2 {mu}s, respectively. The most energetic pulses in our sample have energy fluxes of approximately 100 kJy {mu}s. We have used this large sample to investigate a number of giant pulse emission properties in the Crab pulsar, including correlations among pulse flux density, width, energy flux, phase, and time of arrival. We present a consistent accounting of the probability distributions and threshold cuts in order to reduce pulse-width biases. The excellent sensitivity obtained has allowed us to probe further into the population of giant pulses. We find that a significant portion, no less than 50%, of the overall pulsed energy flux at our observing frequency is emitted in the form of giant pulses.

  14. The C-shunt Flux Qubit: A New Generation of Superconducting Flux Qubit

    NASA Astrophysics Data System (ADS)

    Birenbaum, Jeffrey Scott

    While quantum computation has the potential to revolutionize the scientific community, to date no architecture has been developed which offers the necessary combination of high coherence times and massive scalability. Superconducting flux qubits satisfy the second requirement well but to date useful devices are limited to coherence times of typically only a few mus. In this dissertation we examine the possibilities of improving the coherence performance of the flux qubit to the levels required for fault-tolerant quantum computation. We find that coherence times for many devices are limited by photon-induced quasiparticles and mitigation of these quasiparticles increases coherence times by more than a factor of two. Beyond this, however, we find little improvement in flux qubit performance compared to prior results. Despite improved fabrication techniques and varied device designs we find flux qubit coherence times are still typically below 5 mus. Furthermore, wide device-to-device variations are observed which prevent effective scaling of the flux qubit to quantum information circuits. Based on the proposal by You, et al. we develop of a capacitively-shunted version of the flux qubit called the C-shunt flux qubit. With the addition of a capacitive shunt across the small junction of the flux qubit we are able to reduce the amplitude sensitivity to both charge and flux noise by more than a factor of three. The result is a predicted ten-fold enhancement in the coherence times compared to the unshunted flux qubit. At the same time we preserve much of the anharmonicity of the flux qubit resulting in a device with coherence times comparable to modern transmons but with a factor of four better anharmonicity and more flexible coupling configurations. By using a high-quality MBE aluminum shunt process on an annealed sapphire substrate coupled with a more conventional electron-beam-evaporated aluminum Josephson junction process we fabricate hybrid C-shunt flux qubits. We

  15. Flux Compression Magnetic Nozzle

    NASA Technical Reports Server (NTRS)

    Thio, Y. C. Francis; Schafer, Charles (Technical Monitor)

    2001-01-01

    In pulsed fusion propulsion schemes in which the fusion energy creates a radially expanding plasma, a magnetic nozzle is required to redirect the radially diverging flow of the expanding fusion plasma into a rearward axial flow, thereby producing a forward axial impulse to the vehicle. In a highly electrically conducting plasma, the presence of a magnetic field B in the plasma creates a pressure B(exp 2)/2(mu) in the plasma, the magnetic pressure. A gradient in the magnetic pressure can be used to decelerate the plasma traveling in the direction of increasing magnetic field, or to accelerate a plasma from rest in the direction of decreasing magnetic pressure. In principle, ignoring dissipative processes, it is possible to design magnetic configurations to produce an 'elastic' deflection of a plasma beam. In particular, it is conceivable that, by an appropriate arrangement of a set of coils, a good approximation to a parabolic 'magnetic mirror' may be formed, such that a beam of charged particles emanating from the focal point of the parabolic mirror would be reflected by the mirror to travel axially away from the mirror. The degree to which this may be accomplished depends on the degree of control one has over the flux surface of the magnetic field, which changes as a result of its interaction with a moving plasma.

  16. Superconductor-Diamond Hybrid Quantum System

    NASA Astrophysics Data System (ADS)

    Semba, Kouichi; Yoshihara, Fumiki; Johansson, Jan E. S.; Zhu, Xiaobo; Mizuochi, Norikazu; Munro, William J.; Saito, Shiro; Kakuyanagi, Kosuke; Matsuzaki, Yuichiro

    This chapter describes recent progress on research into superconducting flux qubit, NV diamond, and superconductor-diamond hybrid quantum systems. First, we describe important physical properties of superconducting macroscopic artificial atoms i.e., the tunability of the qubit energy level spacing, the coherence property, an example of strong coupling to another quantum system such as an LC harmonic oscillator, and qubit state readout through a Josephson bifurcation amplifier. We then introduce the NV center in diamond as an intriguing candidate for quantum information processing, which offers excellent multiple accessibility via visible light, microwaves and magnetic fields. Finally, we describe the superconducting flux qubit - NV centers in a diamond hybrid quantum system.

  17. PULSE COUNTER

    DOEpatents

    Trumbo, D.E.

    1959-02-10

    A transistorized pulse-counting circuit adapted for use with nuclear radiation detecting detecting devices to provide a small, light weight portable counter is reported. The small size and low power requirements of the transistor are of particular value in this instance. The circuit provides an adjustable count scale with a single transistor which is triggered by the accumulated charge on a storage capacitor.

  18. Design and functional tests of variable SFQ pulse number multiplier

    NASA Astrophysics Data System (ADS)

    Saito, J.; Tanaka, T.; Moriya, M.; Kobayashi, T.; Mizugaki, Y.; Maezawa, M.

    2011-11-01

    For establishing a new generation of ac voltage standards, digital-to-analog converters (DACs) based on rapid single flux quantum (RSFQ) technology, which enable synthesis of arbitrary waveforms with fundamental accuracy, are developed. An RSFQ-DAC consists of three main subsystems: a pulse-number multiplier (PNM), a pulse distributor (PD) and voltage multipliers (VMs). Conventional RSFQ-DACs generate arbitrary voltages by switching a binary array of the VM cells. In this paper, we propose a Variable-PNM for a new RSFQ-DAC based on frequency modulation. The output voltage is determined by the multiplication factor m of the Variable-PNM that consists of a ring oscillator, an n-bit counter and a decoder. We designed a 2-bit Variable-PNM using the CONNECT cell library. The circuit was fabricated using the ISTEC Nb standard process (STP2). We have confirmed the correct functionalities for 2-, 4-, 6- and 8-fold multiplication in functional testing at low speed.

  19. Magnetic-flux pump

    NASA Technical Reports Server (NTRS)

    Hildebrandt, A. F.; Elleman, D. D.; Whitmore, F. C. (Inventor)

    1966-01-01

    A magnetic flux pump is described for increasing the intensity of a magnetic field by transferring flux from one location to the magnetic field. The device includes a pair of communicating cavities formed in a block of superconducting material, and a piston for displacing the trapped magnetic flux into the secondary cavity producing a field having an intense flux density.

  20. Quantum correlation via quantum coherence

    NASA Astrophysics Data System (ADS)

    Yu, Chang-shui; Zhang, Yang; Zhao, Haiqing

    2014-06-01

    Quantum correlation includes quantum entanglement and quantum discord. Both entanglement and discord have a common necessary condition—quantum coherence or quantum superposition. In this paper, we attempt to give an alternative understanding of how quantum correlation is related to quantum coherence. We divide the coherence of a quantum state into several classes and find the complete coincidence between geometric (symmetric and asymmetric) quantum discords and some particular classes of quantum coherence. We propose a revised measure for total coherence and find that this measure can lead to a symmetric version of geometric quantum correlation, which is analytic for two qubits. In particular, this measure can also arrive at a monogamy equality on the distribution of quantum coherence. Finally, we also quantify a remaining type of quantum coherence and find that for two qubits, it is directly connected with quantum nonlocality.

  1. Rates and quantities of carbon flux to ectomycorrhizal mycelium following 14C pulse labeling of Pinus sylvestris seedlings: effects of litter patches and interaction with a wood-decomposer fungus.

    PubMed

    Leake, J R; Donnelly, D P; Saunders, E M; Boddy, L; Read, D J

    2001-02-01

    We used a novel digital autoradiographic technique that enabled, for the first time, simultaneous visualization and quantification of spatial and temporal changes in carbon allocation patterns in ectomycorrhizal mycelia. Mycorrhizal plants of Pinus sylvestris L. were grown in microcosms containing non-sterile peat. The time course and spatial distribution of carbon allocation by P. sylvestris to mycelia of its mycorrhizal partners, Paxillus involutus (Batsch) Fr. and Suillus bovinus (L.): Kuntze, were quantified following 14C pulse labeling of the plants. Litter patches were used to investigate the effects of nutrient resource quality on carbon allocation. The wood-decomposer fungus Phanerochaete velutina (D.C.: Pers.) Parmasto was introduced to evaluate competitive and territorial interactions between its mycelial cords and the mycelial system of S. bovinus. Growth of ectomycorrhizal mycelium was stimulated in the litter patches. Nearly 60% of the C transferred from host plant to external mycorrhizal mycelium (> 2 mm from root surfaces) was allocated to mycelium in the patches, which comprised only 12% of the soil area available for mycelial colonization. Mycelia in the litter patch most recently colonized by mycorrhizal mycelium received the largest investment of carbon, amounting to 27 to 50% of the total 14C in external mycorrhizal mycelium. The amount of C transfer to external mycelium of S. bovinus following pulse labeling was reduced from a maximum of 167 nmol in systems with no saprotroph to a maximum of 61 nmol in systems interacting with P. velutina. The 14C content of S. bovinus mycelium reached a maximum 24-36 h after labeling in control microcosms, but allocation did not reach a peak until 56 h after labeling, when S. bovinus interacted with mycelium of P. velutina. The mycelium of S. bovinus contained 9% of the total 14C in the plants (including mycorrhizae) at the end of the experiment, but this was reduced to 4% in the presence of P. velutina. The

  2. Flux quench in a system of interacting spinless fermions in one dimension

    NASA Astrophysics Data System (ADS)

    Nakagawa, Yuya O.; Misguich, Grégoire; Oshikawa, Masaki

    2016-05-01

    We study a quantum quench in a one-dimensional spinless fermion model (equivalent to the XXZ spin chain), where a magnetic flux is suddenly switched off. This quench is equivalent to imposing a pulse of electric field and therefore generates an initial particle current. This current is not a conserved quantity in the presence of a lattice and interactions, and we investigate numerically its time evolution after the quench, using the infinite time-evolving block decimation method. For repulsive interactions or large initial flux, we find oscillations that are governed by excitations deep inside the Fermi sea. At long times we observe that the current remains nonvanishing in the gapless cases, whereas it decays to zero in the gapped cases. Although the linear response theory (valid for a weak flux) predicts the same long-time limit of the current for repulsive and attractive interactions (relation with the zero-temperature Drude weight), larger nonlinearities are observed in the case of repulsive interactions compared with that of the attractive case.

  3. Helicity Generation by Heat Pulses

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.; Urrutia, J. M.

    1996-11-01

    In a large laboratory plasma (ne ~= 10^12 cm-3, k Te ~= 2 eV, B0 ~= 30 G, 1 m ⊥ B_0, 2.5 m allel B_0), the electrons are heated locally by a short intense current pulse (100 A, 0.2 μs) using a magnetic loop antenna or a biased electrode. The heat transport along the field establishes a flux tube with strong radial and weak axial temperature gradients. The time scale of temperature relaxation (Δ t ~= 50 μs) is much longer than that of the transient whistler wave pulse excited by the initial current pulse (Δ t < 2 μs). The temperature gradients drive linked field-aligned and diamagnetic currents which, due to their linkage, exhibit helicity and form a flux rope with J × B ~= 0.(R. L. Stenzel and J. M. Urrutia, Phys. Rev. Lett. 76), 1469 (1996). Alternatively, the helicity generation can be understood by the twisting of magnetic field lines which, in the parameter regime of electron MHD, are frozen into the electron fluid. The electron heating at one end of the flux tube causes a nonuniform diamagnetic rotation, hence the helicity. The heat transport by helical convection and conduction is investigated. The slowly time-varying magnetic field may excite Alfvénic perturbations.

  4. D branes in background fluxes and Nielsen-Olesen instabilities

    NASA Astrophysics Data System (ADS)

    Russo, Jorge G.

    2016-06-01

    In quantum field theory, charged particles with spin ≥ 1 may become tachyonic in the present of magnetic fluxes above some critical field, signaling an instability of the vacuum. The phenomenon is generic, in particular, similar instabilities are known to exist in open and closed string theory, where a spinning string state can become tachyonic above a critical field. In compactifications involving RR fluxes F p+2, the quantum states which could become tachyonic by the same Nielsen-Olesen mechanism are D p branes. By constructing an appropriate background with RR magnetic flux that takes into account back-reaction, we identify the possible tachyonic D p brane states and compute the formula for the energy spectrum in a sector. More generally, we argue that in any background RR magnetic flux, there are high spin D p quantum states which become very light at critical fields.

  5. Birefringence effects of short probe pulses of electromagnetically induced transparency

    NASA Astrophysics Data System (ADS)

    Parshkov, Oleg M.; Kochetkova, Anastasia E.; Budyak, Victoria V.

    2016-04-01

    The numerical simulation results of radiations evolution in the presence of electromagnetically induced transparency for J=0-->J=1-->J=2 scheme of degenerate quantum transitions are presented. The pulse regime of wave interaction with Doppler broadening spectral lines was investigated. It was indicated that when the control field is linear polarized, the input circular polarized probe pulse breaks up in the medium into pulses with mutually perpendicular linear polarizations. Polarization direction of one of these pulses coincides with the polarization direction of control fields. The distance, which probe pulse passes in the medium to its full separation, decreases, when input probe pulse duration or control field intensity decreases. The input probe pulse intensity variation almost does not influence separation distance and speed of the linear polarized probe pulses in the medium. The effects, described above, may be interpreted as the birefringence effects of electromagnetically induced transparency in the case of short probe pulse.

  6. Quantum memory Quantum memory

    NASA Astrophysics Data System (ADS)

    Le Gouët, Jean-Louis; Moiseev, Sergey

    2012-06-01

    Interaction of quantum radiation with multi-particle ensembles has sparked off intense research efforts during the past decade. Emblematic of this field is the quantum memory scheme, where a quantum state of light is mapped onto an ensemble of atoms and then recovered in its original shape. While opening new access to the basics of light-atom interaction, quantum memory also appears as a key element for information processing applications, such as linear optics quantum computation and long-distance quantum communication via quantum repeaters. Not surprisingly, it is far from trivial to practically recover a stored quantum state of light and, although impressive progress has already been accomplished, researchers are still struggling to reach this ambitious objective. This special issue provides an account of the state-of-the-art in a fast-moving research area that makes physicists, engineers and chemists work together at the forefront of their discipline, involving quantum fields and atoms in different media, magnetic resonance techniques and material science. Various strategies have been considered to store and retrieve quantum light. The explored designs belong to three main—while still overlapping—classes. In architectures derived from photon echo, information is mapped over the spectral components of inhomogeneously broadened absorption bands, such as those encountered in rare earth ion doped crystals and atomic gases in external gradient magnetic field. Protocols based on electromagnetic induced transparency also rely on resonant excitation and are ideally suited to the homogeneous absorption lines offered by laser cooled atomic clouds or ion Coulomb crystals. Finally off-resonance approaches are illustrated by Faraday and Raman processes. Coupling with an optical cavity may enhance the storage process, even for negligibly small atom number. Multiple scattering is also proposed as a way to enlarge the quantum interaction distance of light with matter. The

  7. Superadiabatic control of quantum operations

    NASA Astrophysics Data System (ADS)

    Vandermause, Jonathan; Ramanathan, Chandrasekhar

    2016-05-01

    Adiabatic pulses are used extensively to enable robust control of quantum operations. We introduce an approach to adiabatic control that uses the superadiabatic quality factor as a performance metric to design robust, high-fidelity pulses. This approach permits the systematic design of quantum control schemes to maximize the adiabaticity of a unitary operation in a particular time interval given the available control resources. The interplay between adiabaticity, fidelity, and robustness of the resulting pulses is examined for the case of single-qubit inversion, and superadiabatic pulses are demonstrated to have improved robustness to control errors. A numerical search strategy is developed to find a broader class of adiabatic operations, including multiqubit adiabatic unitaries. We illustrate the utility of this search strategy by designing control waveforms that adiabatically implement a two-qubit entangling gate for a model NMR system.

  8. Modeling Pulse Tube Cryocoolers with CFD

    NASA Astrophysics Data System (ADS)

    Flake, Barrett; Razani, Arsalan

    2004-06-01

    A commercial computational fluid dynamics (CFD) software package is used to model the oscillating flow inside a pulse tube cryocooler. Capabilities for modeling pulse tubes are demonstrated with preliminary case studies and the results presented. The 2D axi-symmetric simulations demonstrate the time varying temperature and velocity fields in the tube along with computation of the heat fluxes at the hot and cold heat exchangers. The only externally imposed boundary conditions are a cyclically moving piston wall at one end of the tube and constant temperature or heat flux boundaries at the external walls of the hot and cold heat exchangers.

  9. FEU-140 photomultipliers in pulsed plasma spectroscopy

    SciTech Connect

    Arteev, M.S.; Sulakshin, S.S.

    1987-12-01

    Special fast photomultipliers are usually employed in photoelectric spectroscopy of nonstationary plasmas. Measurements have been made on the pulse characteristics and spectral sensitivity for the FEU-140 photomultiplier, which enables one to record a light flux of about 10/sup -10/ W as pulses of duration down to 10 nsec in the range 200-650 nm with a fairly wide linearity range (10/sup -10/-10/sup -18/ W).

  10. Micro pulse lidar

    NASA Technical Reports Server (NTRS)

    Spinhirne, James D.

    1993-01-01

    An eye safe, compact, solid state lidar for profiling atmospheric cloud and aerosol scattering has been demonstrated. The transmitter of the micropulse lidar is a diode pumped micro-J pulse energy, high repetition rate Nd:YLF laser. Eye safety is obtained through beam expansion. The receiver employs a photon counting solid state Geiger mode avalanche photodiode detector. Data acquisition is by a single card multichannel scaler. Daytime background induced quantum noise is controlled by a narrow receiver field-of-view and a narrow bandwidth temperature controlled interference filter. Dynamic range of the signal is limited by optical geometric signal compression. Signal simulations and initial atmospheric measurements indicate that systems built on the micropulse lidar concept are capable of detecting and profiling all significant cloud and aerosol scattering through the troposphere and into the stratosphere. The intended applications are scientific studies and environmental monitoring which require full time, unattended measurements of the cloud and aerosol height structure.

  11. Pulsed hydrojet

    DOEpatents

    Bohachevsky, I.O.; Torrey, M.D.

    1986-06-10

    An underwater pulsed hydrojet propulsion system is provided for accelerating and propelling a projectile or other vessel. A reactant, such as lithium, is fluidized and injected into a water volume. The resulting reaction produces an energy density in a time effective to form a steam pocket. Thrust flaps or baffles direct the pressure from the steam pocket toward an exit nozzle for accelerating a water volume to create thrust. A control system regulates the dispersion of reactant to control thrust characteristics.

  12. Highly indistinguishable photons from deterministic quantum-dot microlenses utilizing three-dimensional in situ electron-beam lithography

    PubMed Central

    Gschrey, M.; Thoma, A.; Schnauber, P.; Seifried, M.; Schmidt, R.; Wohlfeil, B.; Krüger, L.; Schulze, J. -H.; Heindel, T.; Burger, S.; Schmidt, F.; Strittmatter, A.; Rodt, S.; Reitzenstein, S.

    2015-01-01

    The success of advanced quantum communication relies crucially on non-classical light sources emitting single indistinguishable photons at high flux rates and purity. We report on deterministically fabricated microlenses with single quantum dots inside which fulfil these requirements in a flexible and robust quantum device approach. In our concept we combine cathodoluminescence spectroscopy with advanced in situ three-dimensional electron-beam lithography at cryogenic temperatures to pattern monolithic microlenses precisely aligned to pre-selected single quantum dots above a distributed Bragg reflector. We demonstrate that the resulting deterministic quantum-dot microlenses enhance the photon-extraction efficiency to (23±3)%. Furthermore we prove that such microlenses assure close to pure emission of triggered single photons with a high degree of photon indistinguishability up to (80±7)% at saturation. As a unique feature, both single-photon purity and photon indistinguishability are preserved at high excitation power and pulsed excitation, even above saturation of the quantum emitter. PMID:26179766

  13. Highly indistinguishable photons from deterministic quantum-dot microlenses utilizing three-dimensional in situ electron-beam lithography.

    PubMed

    Gschrey, M; Thoma, A; Schnauber, P; Seifried, M; Schmidt, R; Wohlfeil, B; Krüger, L; Schulze, J-H; Heindel, T; Burger, S; Schmidt, F; Strittmatter, A; Rodt, S; Reitzenstein, S

    2015-01-01

    The success of advanced quantum communication relies crucially on non-classical light sources emitting single indistinguishable photons at high flux rates and purity. We report on deterministically fabricated microlenses with single quantum dots inside which fulfil these requirements in a flexible and robust quantum device approach. In our concept we combine cathodoluminescence spectroscopy with advanced in situ three-dimensional electron-beam lithography at cryogenic temperatures to pattern monolithic microlenses precisely aligned to pre-selected single quantum dots above a distributed Bragg reflector. We demonstrate that the resulting deterministic quantum-dot microlenses enhance the photon-extraction efficiency to (23±3)%. Furthermore we prove that such microlenses assure close to pure emission of triggered single photons with a high degree of photon indistinguishability up to (80±7)% at saturation. As a unique feature, both single-photon purity and photon indistinguishability are preserved at high excitation power and pulsed excitation, even above saturation of the quantum emitter. PMID:26179766

  14. Practical quantum coin flipping

    SciTech Connect

    Pappa, Anna; Diamanti, Eleni; Chailloux, Andre; Kerenidis, Iordanis

    2011-11-15

    We show that in the unconditional security model, a single quantum strong coin flip with security guarantees that are strictly better than in any classical protocol is possible to implement with current technology. Our protocol takes into account all aspects of an experimental implementation, including losses, multiphoton pulses emitted by practical photon sources, channel noise, detector dark counts, and finite quantum efficiency. We calculate the abort probability when both players are honest, as well as the probability of one player forcing his desired outcome. For a channel length up to 21 km and commonly used parameter values, we can achieve honest abort and cheating probabilities that are better than in any classical protocol. Our protocol is, in principle, implementable using attenuated laser pulses, with no need for entangled photons or any other specific resources.

  15. Practical quantum coin flipping

    NASA Astrophysics Data System (ADS)

    Pappa, Anna; Chailloux, André; Diamanti, Eleni; Kerenidis, Iordanis

    2011-11-01

    We show that in the unconditional security model, a single quantum strong coin flip with security guarantees that are strictly better than in any classical protocol is possible to implement with current technology. Our protocol takes into account all aspects of an experimental implementation, including losses, multiphoton pulses emitted by practical photon sources, channel noise, detector dark counts, and finite quantum efficiency. We calculate the abort probability when both players are honest, as well as the probability of one player forcing his desired outcome. For a channel length up to 21 km and commonly used parameter values, we can achieve honest abort and cheating probabilities that are better than in any classical protocol. Our protocol is, in principle, implementable using attenuated laser pulses, with no need for entangled photons or any other specific resources.

  16. Adaptive Femtosecond Quantum Control

    NASA Astrophysics Data System (ADS)

    Gerber, Gustav

    2003-03-01

    Obtaining active control over the dynamics of quantum-mechanical systems is a fascinating perspective in modern physics. A promising tool for this purpose is available with femtosecond laser technologies. The intrinsically broad spectral distribution and the phase function of femtosecond laser pulses can be specifically manipulated by pulse shapers to drive molecular systems coherently into the desired reaction pathways [1]. The approach of adaptive femtosecond quantum control follows the suggestion of Judson and Rabitz [2], in which a computer-controlled pulse shaper is used in combination with a learning algorithm [3] and direct feedback from the experiment to achieve coherent control over quantum-mechanical processes in an automated fashion, without requiring any model for the system's response. This technique can be applied to the control of gas-phase photodissociation processes [4]. Different bond-cleaving reactions can be preferentially selected, resulting in chemically different products. Prior knowledge about molecular Hamiltonians or reaction mechanisms is not required in this automated control loop, and this scheme works for complex systems. Adaptive pulse-shaping techniques can be transferred to the control of photoprocesses in the liquid phase as well, motivated by the wish to achieve control at particle densities high enough for (bimolecular) synthetic-chemical applications. Chemically selective molecular excitation is achieved by many-parameter adaptive quantum control [5], despite the failure of typical single-parameter approaches (such as wavelength control, intensity control, or linear chirp control). This experiment demonstrates that photoprocesses in two different molecular species can be controlled simultaneously. Applications are envisioned in bimolecular reaction control where specific educt molecules could selectively be "activated" for purposes of chemical synthesis. A new technological development further increases the possibilities and

  17. Quantum Adiabatic Pumping by Modulating Tunnel Phase in Quantum Dots

    NASA Astrophysics Data System (ADS)

    Taguchi, Masahiko; Nakajima, Satoshi; Kubo, Toshihiro; Tokura, Yasuhiro

    2016-08-01

    In a mesoscopic system, under zero bias voltage, a finite charge is transferred by quantum adiabatic pumping by adiabatically and periodically changing two or more control parameters. We obtained expressions for the pumped charge for a ring of three quantum dots (QDs) by choosing the magnetic flux penetrating the ring as one of the control parameters. We found that the pumped charge shows a steplike behavior with respect to the variance of the flux. The value of the step heights is not universal but depends on the trajectory of the control parameters. We discuss the physical origin of this behavior on the basis of the Fano resonant condition of the ring.

  18. Apparatus and method for optical pulse measurement

    SciTech Connect

    Trebino, R.P.; Tsang, T.; Fittinghoff, D.N.; Sweetser, J.N.; Krumbuegel, M.A.

    1999-12-28

    Practical third-order frequency-resolved optical grating (FROG) techniques for characterization of ultrashort optical pulses are disclosed. The techniques are particularly suited to the measurement of single and/or weak optical pulses having pulse durations in the picosecond and subpicosecond regime. The relative quantum inefficiency of third-order nonlinear optical effects is compensated for through (i) use of phase-matched transient grating beam geometry to maximize interaction length, and (ii) use of interface-enhanced third-harmonic generation.

  19. Apparatus and method for optical pulse measurement

    DOEpatents

    Trebino, Rick P.; Tsang, Thomas; Fittinghoff, David N.; Sweetser, John N.; Krumbuegel, Marco A.

    1999-12-28

    Practical third-order frequency-resolved optical grating (FROG) techniques for characterization of ultrashort optical pulses are disclosed. The techniques are particularly suited to the measurement of single and/or weak optical pulses having pulse durations in the picosecond and subpicosecond regime. The relative quantum inefficiency of third-order nonlinear optical effects is compensated for through i) use of phase-matched transient grating beam geometry to maximize interaction length, and ii) use of interface-enhanced third-harmonic generation.

  20. Nonlinear Optics of Intense Attosecond Light Pulses

    NASA Astrophysics Data System (ADS)

    Nazarkin, Alexander

    2006-10-01

    The interaction of an intense light pulse of "subatomic" duration with a system of multiple discrete quantum states is analyzed. The nonperturbative character of the response to the pulse field leading to an efficient conversion into high order harmonics is predicted. The spatial-temporal evolution of the field is shown to obey a generalized nonlinear wave equation of the double-sine-Gordon type. In addition to the solitary wave structures, it predicts a nontrivial regime of pulse amplification accompanied by extreme temporal self-contraction of the amplified field.

  1. 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.

  2. 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

  3. Qubit lattice coherence induced by electromagnetic pulses in superconducting metamaterials.

    PubMed

    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

  4. Optimal choice of dividing surface for the computation of quantum reaction rates.

    PubMed

    Predescu, Cristian; Miller, William H

    2005-04-14

    We consider the calculation of quantum mechanical rate constants for chemical reactions via algorithms that utilize short-time values of the symmetrized flux-flux correlation function. We argue that the dividing surface that makes optimal use of the short-time quantum information is the surface that minimizes the value at the origin of the symmetrized flux-flux correlation function. We also demonstrate that, in the classical limit, this quantum variational criterion produces the same dividing surface as Wigner's variational principle. Finally, we argue that the quantum variational criterion behaves in a nearly optimal fashion with respect to the minimization of the extent of re-crossing flux. PMID:16851728

  5. Pulsed ion beam source

    DOEpatents

    Greenly, John B.

    1997-01-01

    An improved pulsed ion beam source having a new biasing circuit for the fast magnetic field. This circuit provides for an initial negative bias for the field created by the fast coils in the ion beam source which pre-ionize the gas in the source, ionize the gas and deliver the gas to the proper position in the accelerating gap between the anode and cathode assemblies in the ion beam source. The initial negative bias improves the interaction between the location of the nulls in the composite magnetic field in the ion beam source and the position of the gas for pre-ionization and ionization into the plasma as well as final positioning of the plasma in the accelerating gap. Improvements to the construction of the flux excluders in the anode assembly are also accomplished by fabricating them as layered structures with a high melting point, low conductivity material on the outsides with a high conductivity material in the center.

  6. Implementation of SFQ Microwave Choppers for Controlling Quantum Bits

    NASA Astrophysics Data System (ADS)

    Miura, S.; Takeuchi, N.; Yamanashi, Y.; Yoshikawa, N.

    In order to control the state of qubits by a microwave pulse, the irradiation time and the amplitude have to be controlled precisely. We have developed a single-flux-quantum (SFQ) microwave chopper for high-speed switching of microwave pulses. The proposed chopper is composed of a DC/SFQ convertor, an SFQ switch, a PTL driver, and a superconducting low-pass filter (LPF). The chopper converts an input microwave, which is generated by an external microwave generator at the room temperature, into microwave pulses by using start/stop SFQ control signals. We designed and implemented a microwave chopper module, which can be attached to dilution refrigerators. SFQ chips were fabricated using the ISTEC 2.5 kA/cm2 Nb process. We tested the microwave chopper module at 4.2 K, and demonstrated that a 5-GHz microwave whose amplitude ranging from 0 μV to 150 μV can be chopped by the SFQ control signals.

  7. Controllable injector for local flux entry into superconducting films

    NASA Astrophysics Data System (ADS)

    Carmo, D.; Colauto, F.; de Andrade, A. M. H.; Oliveira, A. A. M.; Ortiz, W. A.; Johansen, T. H.

    2016-09-01

    A superconducting flux injector (SFI) has been designed to allow for controlled injections of magnetic flux into a superconducting film from a predefined location along the edge. The SFI is activated by an external current pulse, here chosen to be 200 ms long, and it is demonstrated on films of Nb that the amount of injected flux is controlled by the pulse height. Examples of injections at two different temperatures where the flux enters by stimulated flux-flow and by triggered thermomagnetic avalanches are presented. The boundary between the two types of injection is determined and discussed. The SFI opens up for active use of phenomena which up to now have been considered hazardous for a safe operation of superconducting devices.

  8. Plasma momentum meter for momentum flux measurements

    DOEpatents

    Zonca, Fulvio; Cohen, Samuel A.; Bennett, Timothy; Timberlake, John R.

    1993-01-01

    Invention comprises an instrument in which momentum flux onto a biasable target plate is transferred via a suspended quartz tube onto a sensitive force transducer--a capacitance-type pressure gauge. The transducer is protected from thermal damage, arcing and sputtering, and materials used in the target and pendulum are electrically insulating, rigid even at elevated temperatures, and have low thermal conductivity. The instrument enables measurement of small forces (10.sup.-5 to 10.sup.3 N) accompanied by high heat fluxes which are transmitted by energetic particles with 10's of eV of kinetic energy in a intense magnetic field and pulsed plasma environment.

  9. 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

  10. Quantum simulation

    NASA Astrophysics Data System (ADS)

    Georgescu, I. M.; Ashhab, S.; Nori, Franco

    2014-01-01

    Simulating quantum mechanics is known to be a difficult computational problem, especially when dealing with large systems. However, this difficulty may be overcome by using some controllable quantum system to study another less controllable or accessible quantum system, i.e., quantum simulation. Quantum simulation promises to have applications in the study of many problems in, e.g., condensed-matter physics, high-energy physics, atomic physics, quantum chemistry, and cosmology. Quantum simulation could be implemented using quantum computers, but also with simpler, analog devices that would require less control, and therefore, would be easier to construct. A number of quantum systems such as neutral atoms, ions, polar molecules, electrons in semiconductors, superconducting circuits, nuclear spins, and photons have been proposed as quantum simulators. This review outlines the main theoretical and experimental aspects of quantum simulation and emphasizes some of the challenges and promises of this fast-growing field.

  11. From reactors to long pulse sources

    SciTech Connect

    Mezei, F. |

    1995-12-31

    We will show, that by using an adapted instrumentation concept, the performance of a continuous source can be emulated by one switch on in long pulses for only about 10% of the total time. This 10 fold gain in neutron economy opens up the way for building reactor like sources with an order of magnitude higher flux than the present technological limits. Linac accelerator driven spallation lends itself favorably for the realization of this kind of long pulse sources, which will be complementary to short pulse spallation sources, the same way continuous reactor sources are.

  12. RSFQ: Ultrafast Logic Based on Magnetic Flux Quantization

    NASA Astrophysics Data System (ADS)

    Likharev, Konstantin

    2000-03-01

    I will review the progress and prospects of Rapid Single-Flux-Quantum (RSFQ) logic family, the newest generation of ultrafast superconductor digital circuits. Elementary cells of this family, based on overdamped Josephson junctions, store and process digital bits in the form of single quanta of magnetic flux, while intercell signaling is provided by picosecond pulses transferred along superconductor microstrip lines, with a speed approaching speed of light. RSFQ integrated circuits may provide the highest speed available in superconductor digital electronics: simple devices like digital frequency dividers have been demonstrated to operate at frequencies up to 770 GHz. Simultaneously, power consumption of RSFQ devices is extremely low (at helium temperatures, about 10-18 Joule per bit), allowing very compact chip packaging, and hence dramatic cuts in the interchip communication latency. Finally, the technology of fabrication of the niobium-based RSFQ circuits is considerably simpler than the standard silicon CMOS process. As a result of the recent work at Stony Brook, HYPRES and elsewhere, relatively complex RSFQ circuits (with thousands of Josephson junctions), including notably the world's fastest analog-to-digital and digital-to-analog converters and digital autocorrelators, have been designed, fabricated, and successfully tested. The main problem with the practical introduction of RSFQ circuits is the necessity of their deep refrigeration. Helium-range closed-cycle refrigerators are still costly and bulky, while HTS RSFQ circuits run into fabrication yield and layout problems. However, for several important applications (including A/D and D/A conversion, digital SQUIDs, RF voltage standards and calibrators, digital correlators, and possibly high-performance computing), the unparalleled performance of LTS RSFQ devices may overweigh the inconvenience of their helium cooling. I will describe the recent advances in these directions, with a special emphasis on the

  13. PULSE COLUMN

    DOEpatents

    Grimmett, E.S.

    1964-01-01

    This patent covers a continuous countercurrent liquidsolids contactor column having a number of contactor states each comprising a perforated plate, a layer of balls, and a downcomer tube; a liquid-pulsing piston; and a solids discharger formed of a conical section at the bottom of the column, and a tubular extension on the lowest downcomer terminating in the conical section. Between the conical section and the downcomer extension is formed a small annular opening, through which solids fall coming through the perforated plate of the lowest contactor stage. This annular opening is small enough that the pressure drop thereacross is greater than the pressure drop upward through the lowest contactor stage. (AEC)

  14. Manipulating Quantum Pathways on the Fly

    NASA Astrophysics Data System (ADS)

    Rey-de-Castro, Roberto; Leghtas, Zaki; Rabitz, Herschel

    2013-05-01

    The expectation value of a quantum system observable can be written as a sum over interfering pathway amplitudes. In this Letter, we demonstrate for the fist time adaptive manipulation of quantum pathways using the Hamiltonian encoding-observable decoding (HE-OD) technique. The principles of HE-OD are illustrated for population transfer in atomic rubidium using shaped femtosecond laser pulses. The ability to manipulate multiple pathway amplitudes is of fundamental importance in all quantum control applications.

  15. Multiple-quantum NMR in solids

    NASA Astrophysics Data System (ADS)

    Yen, Yu-Sze; Pines, A.

    1983-03-01

    Multiple-quantum NMR has typically been observed in small groups of spins in isolated molecules. Due to the profusion of spin transitions in a solid, individual lines are unresolved. Excitation of high quantum transitions by normal schemes is thus difficult. To ensure that overlapping lines add constructively and to enhance sensitivity, time-reversal pulse sequences are used to generate all lines in phase. Up to 22-quantum 1H absorption in solid adamantane is observed.

  16. Multiple-quantum NMR in solids

    SciTech Connect

    Yen, Y.; Pines, A.

    1983-03-15

    Multiple-quantum NMR has typically been observed in small groups of spins in isolated molecules. Due to the profusion of spin transitions in a solid, individual lines are unresolved. Excitation of high quantum transitions by normal schemes is thus difficult. To ensure that overlapping lines add constructively and to enhance sensitivity, time-reversal pulse sequences are used to generate all lines in phase. Up to 22-quantum /sup 1/H absorption in solid adamantane is observed.

  17. Verifiable Quantum Computing

    NASA Astrophysics Data System (ADS)

    Kashefi, Elham

    Over the next five to ten years we will see a state of flux as quantum devices become part of the mainstream computing landscape. However adopting and applying such a highly variable and novel technology is both costly and risky as this quantum approach has an acute verification and validation problem: On the one hand, since classical computations cannot scale up to the computational power of quantum mechanics, verifying the correctness of a quantum-mediated computation is challenging; on the other hand, the underlying quantum structure resists classical certification analysis. Our grand aim is to settle these key milestones to make the translation from theory to practice possible. Currently the most efficient ways to verify a quantum computation is to employ cryptographic methods. I will present the current state of the art of various existing protocols where generally there exists a trade-off between the practicality of the scheme versus their generality, trust assumptions and security level. EK gratefully acknowledges funding through EPSRC Grants EP/N003829/1 and EP/M013243/1.

  18. Quantum-counting CT in the regime of count-rate paralysis: introduction of the pile-up trigger method

    NASA Astrophysics Data System (ADS)

    Kappler, S.; Hölzer, S.; Kraft, E.; Stierstorfer, K.; Flohr, T.

    2011-03-01

    The application of quantum-counting detectors in clinical Computed Tomography (CT) is challenged by extreme X-ray fluxes provided by modern high-power X-ray tubes. Scanning of small objects or sub-optimal patient positioning may lead to situations where those fluxes impinge on the detector without attenuation. Even in operation modes optimized for high-rate applications, with small pixels and high bias voltage, CdTe/CdZnTe detectors deliver pulses in the range of several nanoseconds. This can result in severe pulse pile-up causing detector paralysis and ambiguous detector signals. To overcome this problem we introduce the pile-up trigger, a novel method that provides unambiguous detector signals in rate regimes where classical rising-edge counters run into count-rate paralysis. We present detailed CT image simulations assuming ideal sensor material not suffering from polarization effects at high X-ray fluxes. This way we demonstrate the general feasibility of the pile-up trigger method and quantify resulting imaging properties such as contrasts, image noise and dual-energy performance in the high-flux regime of clinical CT devices.

  19. Vortex Avalanches and Magnetic Flux Fragmentation in Superconductors

    SciTech Connect

    Aranson, Igor; Gurevich, Alex; Vinokur, Valerii

    2001-08-06

    We report the results of numerical simulations of nonisothermal dendritic flux penetration in type-II superconductors. We propose a generic mechanism of dynamic branching of a propagating hot spot of a flux flow/normal state triggered by a local heat pulse. The branching occurs when the flux hot spot reflects from inhomogeneities or the boundary on which magnetization currents either vanish, or change direction. The hot spot then undergoes a cascade of successive splittings, giving rise to a dissipative dendritic-type flux structure. This dynamic state eventually cools down, turning into a frozen multifilamentary pattern of magnetization currents.

  20. Phase control of a two-photon transition with shaped femtosecond laser-pulse sequences

    SciTech Connect

    Praekelt, A.; Wollenhaupt, M.; Sarpe-Tudoran, C.; Baumert, T.

    2004-12-01

    Phase effects in a quantum control experiment on the two-photon transition 4s <-<- 3s of atomic sodium are studied. In our experiment, we combine the generation of phase-locked interferometrically generated pulses with pulse-shaping techniques to study in detail the interplay of optical and quantum-mechanical phases. Subtle differences in the physical realization of the pulse sequences produce large difference in the control objective--the 4s population. The control mechanisms of more complex pulse sequences generated by periodic and discontinuous phase-modulation functions are investigated systematically and analyzed on the basis of quantum-mechanical interference.

  1. Generation of short and intense attosecond pulses

    NASA Astrophysics Data System (ADS)

    Khan, Sabih Ud Din

    Extremely broad bandwidth attosecond pulses (which can support 16as pulses) have been demonstrated in our lab based on spectral measurements, however, compensation of intrinsic chirp and their characterization has been a major bottleneck. In this work, we developed an attosecond streak camera using a multi-layer Mo/Si mirror (bandwidth can support ˜100as pulses) and position sensitive time-of-flight detector, and the shortest measured pulse was 107.5as using DOG, which is close to the mirror bandwidth. We also developed a PCGPA based FROG-CRAB algorithm to characterize such short pulses, however, it uses the central momentum approximation and cannot be used for ultra-broad bandwidth pulses. To facilitate the characterization of such pulses, we developed PROOF using Fourier filtering and an evolutionary algorithm. We have demonstrated the characterization of pulses with a bandwidth corresponding to ˜20as using synthetic data. We also for the first time demonstrated single attosecond pulses (SAP) generated using GDOG with a narrow gate width from a multi-cycle driving laser without CE-phase lock, which opens the possibility of scaling attosecond photon flux by extending the technique to peta-watt class lasers. Further, we generated intense attosecond pulse trains (APT) from laser ablated carbon plasmas and demonstrated ˜9.5 times more intense pulses as compared to those from argon gas and for the first time demonstrated a broad continuum from a carbon plasma using DOG. Additionally, we demonstrated ˜100 times enhancement in APT from gases by switching to 400 nm (blue) driving pulses instead of 800 nm (red) pulses. We measured the ellipticity dependence of high harmonics from blue pulses in argon, neon and helium, and developed a simple theoretical model to numerically calculate the ellipticity dependence with good agreement with experiments. Based on the ellipticity dependence, we proposed a new scheme of blue GDOG which we predict can be employed to extract

  2. The Quantasyn, an improved quantum detector

    NASA Technical Reports Server (NTRS)

    Gorstein, M.; Mc Williams, I. G.; Seward, H. H.

    1969-01-01

    Quantasyn provides absolute measurement of radiation flux in the range 1000 A to 4500 A and into the vacuum ultraviolet. This radiation detector cimbines the high quantum efficiency and inherent linearity of the silicon solar cell with the constant quantum response of the fluorescent organic compound liumogen.

  3. The Reality of the Quantum World.

    ERIC Educational Resources Information Center

    Shimony, Abner

    1988-01-01

    Describes experiments used during recent history to explain the nature of the quantum world. Explains the essential elements of experiments using polarized light and magnetic flux. Illustrates differences between classical theories in physics and quantum theory. Shows how experiments in the microscopic and macroscopic world appear to support…

  4. Quantum networks reveal quantum nonlocality.

    PubMed

    Cavalcanti, Daniel; Almeida, Mafalda L; Scarani, Valerio; Acín, Antonio

    2011-01-01

    The results of local measurements on some composite quantum systems cannot be reproduced classically. This impossibility, known as quantum nonlocality, represents a milestone in the foundations of quantum theory. Quantum nonlocality is also a valuable resource for information-processing tasks, for example, quantum communication, quantum key distribution, quantum state estimation or randomness extraction. Still, deciding whether a quantum state is nonlocal remains a challenging problem. Here, we introduce a novel approach to this question: we study the nonlocal properties of quantum states when distributed and measured in networks. We show, using our framework, how any one-way entanglement distillable state leads to nonlocal correlations and prove that quantum nonlocality is a non-additive resource, which can be activated. There exist states, local at the single-copy level, that become nonlocal when taking several copies of them. Our results imply that the nonlocality of quantum states strongly depends on the measurement context. PMID:21304513

  5. Programmable quantum simulation by dynamic Hamiltonian engineering

    NASA Astrophysics Data System (ADS)

    Hayes, David; Flammia, Steven T.; Biercuk, Michael J.

    2014-08-01

    Quantum simulation is a promising near term application for quantum information processors with the potential to solve computationally intractable problems using just a few dozen interacting qubits. A range of experimental platforms have recently demonstrated the basic functionality of quantum simulation applied to quantum magnetism, quantum phase transitions and relativistic quantum mechanics. However, in all cases, the physics of the underlying hardware restricts the achievable inter-particle interactions and forms a serious constraint on the versatility of the simulators. To broaden the scope of these analog devices, we develop a suite of pulse sequences that permit a user to efficiently realize average Hamiltonians that are beyond the native interactions of the system. Specifically, this approach permits the generation of all symmetrically coupled translation-invariant two-body Hamiltonians with homogeneous on-site terms, a class which includes all spin-1/2 XYZ chains, but generalized to include long-range couplings. Our work builds on previous work proving that universal simulation is possible using both entangling gates and single-qubit unitaries. We show that determining the appropriate ‘program’ of unitary pulse sequences which implements an arbitrary Hamiltonian transformation can be formulated as a linear program over functions defined by those pulse sequences, running in polynomial time and scaling efficiently in hardware resources. Our analysis extends from circuit model quantum information to adiabatic quantum evolutions, representing an important and broad-based success in applying functional analysis to the field of quantum information.

  6. Graphene quantum interference photodetector

    PubMed Central

    Voss, Paul L

    2015-01-01

    Summary In this work, a graphene quantum interference (QI) photodetector was simulated in two regimes of operation. The structure consists of a graphene nanoribbon, Mach–Zehnder interferometer (MZI), which exhibits a strongly resonant transmission of electrons of specific energies. In the first regime of operation (that of a linear photodetector), low intensity light couples two resonant energy levels, resulting in scattering and differential transmission of current with an external quantum efficiency of up to 5.2%. In the second regime of operation, full current switching is caused by the phase decoherence of the current due to a strong photon flux in one or both of the interferometer arms in the same MZI structure. Graphene QI photodetectors have several distinct advantages: they are of very small size, they do not require p- and n-doped regions, and they exhibit a high external quantum efficiency. PMID:25821713

  7. Quantum Computation with Phase Drift Errors

    NASA Astrophysics Data System (ADS)

    Miquel, César; Paz, Juan Pablo; Zurek, Wojciech Hubert

    1997-05-01

    We numerically simulate the evolution of an ion trap quantum computer made out of 18 ions subject to a sequence of nearly 15 000 laser pulses in order to find the prime factors of N = 15. We analyze the effect of random and systematic phase drift errors arising from inaccuracies in the laser pulses which induce over (under) rotation of the quantum state. Simple analytic estimates of the tolerance for the quality of driving pulses are presented. We examine the use of watchdog stabilization to partially correct phase drift errors concluding that, in the regime investigated, it is rather inefficient.

  8. Homopolar Gun for Pulsed Spheromak Fusion Reactors II

    SciTech Connect

    Fowler, T

    2004-06-14

    A homopolar gun is discussed that could produce the high currents required for pulsed spheromak fusion reactors even with unit current amplification and open field lines during injection, possible because close coupling between the gun and flux conserver reduces gun losses to acceptable levels. Example parameters are given for a gun compatible with low cost pulsed reactors and for experiments to develop the concept.

  9. Quantum ontologies

    SciTech Connect

    Stapp, H.P.

    1988-12-01

    Quantum ontologies are conceptions of the constitution of the universe that are compatible with quantum theory. The ontological orientation is contrasted to the pragmatic orientation of science, and reasons are given for considering quantum ontologies both within science, and in broader contexts. The principal quantum ontologies are described and evaluated. Invited paper at conference: Bell's Theorem, Quantum Theory, and Conceptions of the Universe, George Mason University, October 20-21, 1988. 16 refs.

  10. Error-corrected quantum annealing with hundreds of qubits

    NASA Astrophysics Data System (ADS)

    Pudenz, Kristen L.; Albash, Tameem; Lidar, Daniel A.

    2014-02-01

    Quantum information processing offers dramatic speedups, yet is susceptible to decoherence, whereby quantum superpositions decay into mutually exclusive classical alternatives, thus robbing quantum computers of their power. This makes the development of quantum error correction an essential aspect of quantum computing. So far, little is known about protection against decoherence for quantum annealing, a computational paradigm aiming to exploit ground-state quantum dynamics to solve optimization problems more rapidly than is possible classically. Here we develop error correction for quantum annealing and experimentally demonstrate it using antiferromagnetic chains with up to 344 superconducting flux qubits in processors that have recently been shown to physically implement programmable quantum annealing. We demonstrate a substantial improvement over the performance of the processors in the absence of error correction. These results pave the way towards large-scale noise-protected adiabatic quantum optimization devices, although a threshold theorem such as has been established in the circuit model of quantum computing remains elusive.

  11. Changes in luminescence emission induced by proton irradiation: InGaAs/GaAs quantum wells and quantum dots

    NASA Technical Reports Server (NTRS)

    Leon, R.; Swift, G. M.; Magness, B.; Taylor, W. A.; Tang, Y. S.; Wang, K. L.; Dowd, P.; Zhang, Y. H.

    2000-01-01

    The photoluminescence emission from InGaAs/GaAs quantum-well and quantum-dot (QD) structures are compared after controlled irradiation with 1.5 MeV proton fluxes. Results presented here show a significant enhancement in radiation tolerance with three-dimensional quantum confinement.

  12. Robust coherent superposition of states by single-shot shaped pulse

    NASA Astrophysics Data System (ADS)

    Ndong, Mamadou; Djotyan, Gagik; Ruschhaupt, Andreas; Guérin, Stéphane

    2015-09-01

    We adapt a single-shot shaped pulse technique to produce robust coherent superpositions of quantum states with a high fidelity of control. We derive simple pulses of low areas for the corresponding Rabi frequency which are robust with respect to pulse area imperfections. Such features of robustness, high-fidelity, and low Rabi frequency area are crucial steps towards the experimental implementation of scalable quantum gates.

  13. Quantum Computer Games: Quantum Minesweeper

    ERIC Educational Resources Information Center

    Gordon, Michal; Gordon, Goren

    2010-01-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical…

  14. Controlling VUV photon fluxes in low-pressure inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Tian, Peng; Kushner, Mark J.

    2015-06-01

    Low-pressure (a few to hundreds of millitorrs) inductively coupled plasmas (ICPs), as typically used in microelectronics fabrication, often produce vacuum-ultraviolet (VUV) photon fluxes onto surfaces comparable to or exceeding the magnitude of ion fluxes. These VUV photon fluxes are desirable in applications such as sterilization of medical equipment but are unwanted in many materials fabrication processes due to damage to the devices by the high-energy photons. Under specific conditions, VUV fluxes may stimulate etching or synergistically combine with ion fluxes to modify polymeric materials. In this regard, it is desirable to control the magnitude of VUV fluxes or the ratio of VUV fluxes to those of other reactive species, such as ions, or to discretely control the VUV spectrum. In this paper, we discuss results from a computational investigation of VUV fluxes from low-pressure ICPs sustained in rare gas mixtures. The control of VUV fluxes through the use of pressure, pulsed power, and gas mixture is discussed. We found that the ratio, β, of VUV photon to ion fluxes onto surfaces generally increases with increasing pressure. When using pulsed plasmas, the instantaneous value of β can vary by a factor of 4 or more during the pulse cycle due to the VUV flux more closely following the pulsed power.

  15. Cosmic string formation by flux trapping

    SciTech Connect

    Blanco-Pillado, Jose J.; Olum, Ken D.; Vilenkin, Alexander

    2007-11-15

    We study the formation of cosmic strings by confining a stochastic magnetic field into flux tubes in a numerical simulation. We use overdamped evolution in a potential that is minimized when the flux through each face in the simulation lattice is a multiple of the fundamental flux quantum. When the typical number of flux quanta through a correlation-length-sized region is initially about 1, we find a string network similar to that generated by the Kibble-Zurek mechanism. With larger initial flux, the loop distribution and the Brownian shape of the infinite strings remain unchanged, but the fraction of length in infinite strings is increased. A 2D slice of the network exhibits bundles of strings pointing in the same direction, as in earlier 2D simulations. We find, however, that strings belonging to the same bundle do not stay together in 3D for much longer than the correlation length. As the initial flux per correlation length is decreased, there is a point at which infinite strings disappear, as in the Hagedorn transition.

  16. Realization of a universal and phase-covariant quantum cloning machine in separate cavities

    SciTech Connect

    Fang Baolong; Song Qingming; Ye Liu

    2011-04-15

    We present a scheme to realize a special quantum cloning machine in separate cavities. The quantum cloning machine can copy the quantum information from a photon pulse to two distant atoms. Choosing the different parameters, the method can perform optimal symmetric (asymmetric) universal quantum cloning and optimal symmetric (asymmetric) phase-covariant cloning.

  17. Exact transient photon correlation with arbitrary laser pulses

    SciTech Connect

    Ooi, C. H. Raymond

    2011-11-15

    We present a full quantum theory to study the transient evolution of photon pairs. We introduce a method which gives exact time-dependent solutions of the coupled quantum Langevin equations for a multilevel quantum particle driven by arbitrary time-dependent laser fields. The analytical solutions are used to develop a numerical code for computing exact time evolution of the two-photon correlation function. We analyze the effects of laser pulses sequence, pulse duration, chirping, and initial internal quantum states on the nonclassicality of the photon correlation through the violation of the Cauchy-Schwarz inequality. The results provide a promising possibility of controlling the generation of highly correlated photon pairs using tailored short laser pulses.

  18. InP-based type-I quantum well lasers up to 2.9 μm at 230 K in pulsed mode on a metamorphic buffer

    SciTech Connect

    Gu, Y.; Zhang, Y. G. Ma, Y. J.; Zhou, L.; Chen, X. Y.; Xi, S. P.; Du, B.

    2015-03-23

    This work reports on up to 2.9 μm lasing at 230 K of InP-based type-I quantum well lasers. This record long wavelength lasing is achieved by applying InP-based Sb-free structures with eight periods of strain-compensated InAs quantum wells grown on metamorphic In{sub 0.8}Al{sub 0.2}As template layers. The continuous-wave threshold current density is 797 A/cm{sup 2} and the idealized extrapolated threshold current density for infinite cavity length is as low as 58 A/cm{sup 2} per quantum well at 120 K. This scheme is a promising pathway for extending the wavelength range of type-I quantum well lasers on InP substrates.

  19. Uniqueness of measures in loop quantum cosmology

    SciTech Connect

    Hanusch, Maximilian

    2015-09-15

    In Ashtekar and Campiglia [Classical Quantum Gravity 29, 242001 (2012)], residual diffeomorphisms have been used to single out the standard representation of the reduced holonomy-flux algebra in homogeneous loop quantum cosmology (LQC). We show that, in the homogeneous isotropic case, unitarity of the translations with respect to the extended ℝ-action (exponentiated reduced fluxes in the standard approach) singles out the Bohr measure on both the standard quantum configuration space ℝ{sub Bohr} as well as on the Fleischhack one (ℝ⊔ℝ{sub Bohr}). Thus, in both situations, the same condition singles out the standard kinematical Hilbert space of LQC.

  20. Synthetic magnetic fluxes on the honeycomb lattice

    SciTech Connect

    Gorecka, Agnieszka; Gremaud, Benoit; Miniatura, Christian

    2011-08-15

    We devise experimental schemes that are able to mimic uniform and staggered magnetic fluxes acting on ultracold two-electron atoms, such as ytterbium atoms, propagating in a honeycomb lattice. The atoms are first trapped into two independent state-selective triangular lattices and then further exposed to a suitable configuration of resonant Raman laser beams. These beams induce hops between the two triangular lattices and make atoms move in a honeycomb lattice. Atoms traveling around each unit cell of this honeycomb lattice pick up a nonzero phase. In the uniform case, the artificial magnetic flux sustained by each cell can reach about two flux quanta, thereby realizing a cold-atom analog of the Harper model with its notorious Hofstadter's butterfly structure. Different condensed-matter phenomena such as the relativistic integer and fractional quantum Hall effects, as observed in graphene samples, could be targeted with this scheme.

  1. Magnetic Flux Quantization of the Landau Problem

    NASA Astrophysics Data System (ADS)

    Wang, Jianhua; Li, Kang; Long, Shuming; Yuan, Yi

    2014-08-01

    Landau problem has a very important application in modern physics, in which two-dimensional electron gas system and quantum Hall effect are outstanding. In this paper, first we review the solution of the Pauli equation, then using the single electron wave function, we calculate moving area expectations of the ideal 2-dimensional electron gas system and the per unit area's degeneracy of the electron gas system. As a result, how to calculate the magnetic flux of the electron gas system is given. It shows that the magnetic flux of 2-dimensional electron gas system in magnetic field is quantized, and magnetic flux quantization results from the quantization of the moving area expectations of electron gas system.

  2. Pulse energy measurement at the SXR instrument

    DOE PAGESBeta

    Moeller, Stefan; Brown, Garth; Dakovski, Georgi; Hill, Bruce; Holmes, Michael; Loos, Jennifer; Maida, Ricardo; Paiser, Ernesto; Schlotter, William; Turner, Joshua J.; et al

    2015-04-14

    A gas monitor detector was implemented and characterized at the Soft X-ray Research (SXR) instrument to measure the average, absolute and pulse-resolved photon flux of the LCLS beam in the energy range between 280 and 2000 eV. The detector is placed after the monochromator and addresses the need to provide reliable absolute pulse energy as well as pulse-resolved measurements for the various experiments at this instrument. This detector provides a reliable non-invasive measurement for determining flux levels on the samples in the downstream experimental chamber and for optimizing signal levels of secondary detectors and for the essential need of datamore » normalization. The design, integration into the instrument and operation are described, and examples of its performance are given.« less

  3. Pulse energy measurement at the SXR instrument

    SciTech Connect

    Moeller, Stefan; Brown, Garth; Dakovski, Georgi; Hill, Bruce; Holmes, Michael; Loos, Jennifer; Maida, Ricardo; Paiser, Ernesto; Schlotter, William; Turner, Joshua J.; Wallace, Alex; Jastrow, Ulf; Kreis, Svea; Sorokin, Andrey A.; Tiedtke, Kai

    2015-04-14

    A gas monitor detector was implemented and characterized at the Soft X-ray Research (SXR) instrument to measure the average, absolute and pulse-resolved photon flux of the LCLS beam in the energy range between 280 and 2000 eV. The detector is placed after the monochromator and addresses the need to provide reliable absolute pulse energy as well as pulse-resolved measurements for the various experiments at this instrument. This detector provides a reliable non-invasive measurement for determining flux levels on the samples in the downstream experimental chamber and for optimizing signal levels of secondary detectors and for the essential need of data normalization. The design, integration into the instrument and operation are described, and examples of its performance are given.

  4. Pulse energy measurement at the SXR instrument

    PubMed Central

    Moeller, Stefan; Brown, Garth; Dakovski, Georgi; Hill, Bruce; Holmes, Michael; Loos, Jennifer; Maida, Ricardo; Paiser, Ernesto; Schlotter, William; Turner, Joshua J.; Wallace, Alex; Jastrow, Ulf; Kreis, Svea; Sorokin, Andrey A.; Tiedtke, Kai

    2015-01-01

    A gas monitor detector was implemented and characterized at the Soft X-ray Research (SXR) instrument to measure the average, absolute and pulse-resolved photon flux of the LCLS beam in the energy range between 280 and 2000 eV. The detector is placed after the monochromator and addresses the need to provide reliable absolute pulse energy as well as pulse-resolved measurements for the various experiments at this instrument. This detector provides a reliable non-invasive measurement for determining flux levels on the samples in the downstream experimental chamber and for optimizing signal levels of secondary detectors and for the essential need of data normalization. The design, integration into the instrument and operation are described, and examples of its performance are given. PMID:25931075

  5. Loads for pulsed power cylindrical implosion experiments

    SciTech Connect

    Anderson, W.E.; Armijo, E.V.; Barthell, B.L.; Bartos, J.J.; Bush, H.; Foreman, L.R.; Garcia, F.P.; Gobby, P.L.; Gomez, V.M.; Gurule, V.A.

    1994-07-01

    Pulse power can be used to generate high energy density conditions in convergent hollow cylindrical geometry through the use of appropriate electrode configuration and cylindrical loads. Cylindrically symmetric experiments are conducted with the Pegasus-H inductive store, capacitor energized pulse power facility at Los Alamos using both precision machined cylindrical liner loads and low mass vapor deposited cylindrical foil loads. The liner experiments investigate solid density hydrodynamic topics. Foil loads vaporize from Joule heating to generate an imploding cylindrical plasma which can be used to simulate some fluxes associated with fusion energy processes. Similar experiments are conducted with {open_quotes}Procyon{close_quotes} inductive store pulse power assemblies energized by explosively driven magnetic flux compression.

  6. High fidelity quantum memory via dynamical decoupling: theory and experiment

    NASA Astrophysics Data System (ADS)

    Peng, Xinhua; Suter, Dieter; Lidar, Daniel A.

    2011-08-01

    Quantum information processing requires overcoming decoherence—the loss of 'quantumness' due to the inevitable interaction between the quantum system and its environment. One approach towards a solution is quantum dynamical decoupling—a method employing strong and frequent pulses applied to the qubits. Here we report on the first experimental test of the concatenated dynamical decoupling (CDD) scheme, which invokes recursively constructed pulse sequences. Using nuclear magnetic resonance, we demonstrate a near order of magnitude improvement in the decay time of stored quantum states. In conjunction with recent results on high fidelity quantum gates using CDD, our results suggest that quantum dynamical decoupling should be used as a first layer of defense against decoherence in quantum information processing implementations, and can be a stand-alone solution in the right parameter regime.

  7. Analytical optimal pulse shapes obtained with the aid of genetic algorithms

    NASA Astrophysics Data System (ADS)

    Guerrero, Rubén D.; Arango, Carlos A.; Reyes, Andrés

    2015-09-01

    We propose a methodology to design optimal pulses for achieving quantum optimal control on molecular systems. Our approach constrains pulse shapes to linear combinations of a fixed number of experimentally relevant pulse functions. Quantum optimal control is obtained by maximizing a multi-target fitness function using genetic algorithms. As a first application of the methodology, we generated an optimal pulse that successfully maximized the yield on a selected dissociation channel of a diatomic molecule. Our pulse is obtained as a linear combination of linearly chirped pulse functions. Data recorded along the evolution of the genetic algorithm contained important information regarding the interplay between radiative and diabatic processes. We performed a principal component analysis on these data to retrieve the most relevant processes along the optimal path. Our proposed methodology could be useful for performing quantum optimal control on more complex systems by employing a wider variety of pulse shape functions.

  8. Analytical optimal pulse shapes obtained with the aid of genetic algorithms

    SciTech Connect

    Guerrero, Rubén D.; Arango, Carlos A.; Reyes, Andrés

    2015-09-28

    We propose a methodology to design optimal pulses for achieving quantum optimal control on molecular systems. Our approach constrains pulse shapes to linear combinations of a fixed number of experimentally relevant pulse functions. Quantum optimal control is obtained by maximizing a multi-target fitness function using genetic algorithms. As a first application of the methodology, we generated an optimal pulse that successfully maximized the yield on a selected dissociation channel of a diatomic molecule. Our pulse is obtained as a linear combination of linearly chirped pulse functions. Data recorded along the evolution of the genetic algorithm contained important information regarding the interplay between radiative and diabatic processes. We performed a principal component analysis on these data to retrieve the most relevant processes along the optimal path. Our proposed methodology could be useful for performing quantum optimal control on more complex systems by employing a wider variety of pulse shape functions.

  9. Quantum information processing with trapped ion chains

    NASA Astrophysics Data System (ADS)

    Manning, Timothy Andrew

    Trapped atomic ion systems are currently the most advanced platform for quantum information processing. Their long coherence times, pristine state initialization and detection, and precisely controllable and versatile interactions make them excellent quantum systems for experiments in quantum computation and quantum simulation. One of the more promising schemes for quantum computing consists of performing single and multi-qubit quantum gates on qubits in a linear ion crystal. Some of the key challenges of scaling such a system are the individual addressing of arbitrary subsets of ions and controlling the growing complexity of motional mode interactions as the number of qubits increases or when the gates are performed faster. Traditional entangling quantum gates between ion qubits use laser pulses to couple the qubit states to the collective motion of the crystal, thereby generating a spin-spin interaction that can produce entanglement between selected qubits. The intrinsic limitations on the performance of gates using this method can be alleviated by applying optimally shaped pulses instead of pulses with constant amplitude. This thesis explains the theory behind this pulse shaping scheme and how it is implemented on a chain of Yb ions held in a linear radiofrequency 'Paul' trap. Several experiments demonstrate the technique in chains of two, three, and five ions using various types of pulse shapes. A tightly focused individual addressing beam allows us to apply the entangling gates to a target pair of ions, and technical issues related to such tight focusing are discussed. Other advantages to the pulse shaping scheme include a robustness against detuning errors and the possibility of suppressing undesirable coupling due to optical spillover on neighboring ions. Combined with ion shuttling, we harness these features to perform sequential gates to different qubit pairs in order to create genuine tripartite entangled states and demonstrate the programmable quantum

  10. Quantum memristors

    NASA Astrophysics Data System (ADS)

    Pfeiffer, P.; Egusquiza, I. L.; di Ventra, M.; Sanz, M.; Solano, E.

    2016-07-01

    Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems.

  11. Quantum memristors.

    PubMed

    Pfeiffer, P; Egusquiza, I L; Di Ventra, M; Sanz, M; Solano, E

    2016-01-01

    Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems. PMID:27381511

  12. Quantum memristors

    PubMed Central

    Pfeiffer, P.; Egusquiza, I. L.; Di Ventra, M.; Sanz, M.; Solano, E.

    2016-01-01

    Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems. PMID:27381511

  13. Temporal compression of quantum-information-carrying photons using a photon-echo quantum memory approach

    SciTech Connect

    Moiseev, S. A.; Tittel, W.

    2010-07-15

    We study quantum compression and decompression of light pulses that carry quantum information using a photon-echo quantum memory technique with controllable inhomogeneous broadening of an isolated atomic absorption line. We investigate media with differently broadened absorption profiles, transverse and longitudinal, finding that the recall efficiency can be as large as unity and that the quantum information encoded into the photonic qubits can remain unperturbed. Our results provide insight into reversible light-atom interaction and are interesting in view of future quantum communication networks, where pulse compression and decompression may play an important role in increasing the qubit rate or in mapping quantum information from photonic carriers with large optical bandwidth into atomic memories with smaller bandwidth.

  14. Temporal compression of quantum-information-carrying photons using a photon-echo quantum memory approach

    NASA Astrophysics Data System (ADS)

    Moiseev, S. A.; Tittel, W.

    2010-07-01

    We study quantum compression and decompression of light pulses that carry quantum information using a photon-echo quantum memory technique with controllable inhomogeneous broadening of an isolated atomic absorption line. We investigate media with differently broadened absorption profiles, transverse and longitudinal, finding that the recall efficiency can be as large as unity and that the quantum information encoded into the photonic qubits can remain unperturbed. Our results provide insight into reversible light-atom interaction and are interesting in view of future quantum communication networks, where pulse compression and decompression may play an important role in increasing the qubit rate or in mapping quantum information from photonic carriers with large optical bandwidth into atomic memories with smaller bandwidth.

  15. Quantifying the extent of recrossing flux for quantumsystems

    SciTech Connect

    Small, Michael S.; Predescu, Cristian; Miller, William H.

    2005-04-19

    We present arguments demonstrating that the Miller, Schwartz, and Tromp (MST) correlation function is the only computationally reasonable choice with regard to minimizing the extent of recrossing flux. However, using accurate numerical results, we point out that the MST flux-flux correlation function almost always exhibits non-vanishing negative parts, even for the simplest physical systems. We argue that, in order to best handle the residual recrossing flux, one must not rely on the ''no recrossing'' assumption in the development of quantum transition state theories. To provide accurate numerical examples, we derive the analytical expressions for the flux-flux correlation and spectral functions for the symmetric Eckart and rectangular potential barriers.

  16. Return flux experiment

    NASA Technical Reports Server (NTRS)

    Tveekrem, June L.

    1992-01-01

    All spacecraft emit molecules via outgassing, thruster plumes, vents, etc. The return flux is the portion of those molecules that scatter from the ambient atmosphere and return to the spacecraft. Return flux allows critical spacecraft surfaces to become contaminated even when there is no direct line of sight between the contamination source and the critical surface. Data from the Long Duration Exposure Facility (LDEF) show that contamination of LDEF surfaces could not have come entirely from direct flux. The data suggest significant return flux. Several computer models have been developed to simulate return flux, but the predictions have never been verified in orbit. Large uncertainties in predictions lead to overly conservative spacecraft designs. The purpose of the REturn FLux EXperiment (REFLEX) is to fly a controlled experiment that can be directly compared with predictions from several models.

  17. Unconditional room-temperature quantum memory

    NASA Astrophysics Data System (ADS)

    Hosseini, M.; Campbell, G.; Sparkes, B. M.; Lam, P. K.; Buchler, B. C.

    2011-10-01

    Just as classical information systems require buffers and memory, the same is true for quantum information systems. The potential that optical quantum information processing holds for revolutionizing computation and communication is therefore driving significant research into developing optical quantum memory. A practical optical quantum memory must be able to store and recall quantum states on demand with high efficiency and low noise. Ideally, the platform for the memory would also be simple and inexpensive. Here, we present a complete tomographic reconstruction of quantum states that have been stored in the ground states of rubidium in a vapour cell operating at around 80°C. Without conditional measurements, we show recall fidelity up to 98% for coherent pulses containing around one photon. To unambiguously verify that our memory beats the quantum no-cloning limit we employ state-independent verification using conditional variance and signal-transfer coefficients.

  18. 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.

  19. ADJUSTABLE DOUBLE PULSE GENERATOR

    DOEpatents

    Gratian, J.W.; Gratian, A.C.

    1961-08-01

    >A modulator pulse source having adjustable pulse width and adjustable pulse spacing is described. The generator consists of a cross coupled multivibrator having adjustable time constant circuitry in each leg, an adjustable differentiating circuit in the output of each leg, a mixing and rectifying circuit for combining the differentiated pulses and generating in its output a resultant sequence of negative pulses, and a final amplifying circuit for inverting and square-topping the pulses. (AEC)

  20. Thermodynamics of quantum heat engines

    NASA Astrophysics Data System (ADS)

    Goswami, Himangshu Prabal; Harbola, Upendra

    2013-07-01

    We consider a recently proposed four-level quantum heat engine (QHE) model to analyze the role of quantum coherences in determining the thermodynamic properties of the engine, such as flux, output power, and efficiency. A quantitative analysis of the relative effects of the coherences induced by the two thermal baths is brought out. By taking account of the dissipation in the cavity mode, we define useful work obtained from the QHE and present some analytical results for the optimal values of relative coherences that maximizes flux (hence output power) through the engine. We also analyze the role of quantum effects in inducing population inversion (lasing) between the states coupled to the cavity mode. The universal behavior of the efficiency at maximum power (EMP) is examined. In accordance with earlier theoretical predictions, to leading order, we find that EMP˜ηc/2, where ηc is Carnot efficiency. However, the next higher order coefficient is system dependent and hence nonuniversal.

  1. Heat flux measurements

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Weikle, Donald H.

    1989-01-01

    A new automated, computer controlled heat flux measurement facility is described. Continuous transient and steady-state surface heat flux values varying from about 0.3 to 6 MW/sq m over a temperature range of 100 to 1200 K can be obtained in the facility. An application of this facility is the development of heat flux gauges for continuous fast transient surface heat flux measurement on turbine blades operating in space shuttle main engine turbopumps. The facility is useful for durability testing at fast temperature transients.

  2. Aspects of flux compactification

    NASA Astrophysics Data System (ADS)

    Liu, Tao

    In this thesis, we study three main aspects of flux compactifications: (1) classify supergravity solutions from flux compactification; (2) construct flux-deformed geometry and 4D low-energy theory to describe these flux vacua; and (3) study 4D particle phenomenology and cosmology of flux vacua. In the first part, we review G-structure, the basic tool to study supersymmetric flux solutions, and some typical solutions obtained in heterotic, type IIA and type IIB string theories. Then we present a comprehensive classification of supersymmetric vacua of M-theory compactification on 7D manifolds with general four-form fluxes. We analyze the cases where the resulting four-dimensional vacua have N = 1, 2, 3, 4 supersymmetry and the internal space allows for SU(2)-, SU(3)- or G 2-structures. In particular, we find for N = 2 supersymmetry, that the external space-time is Minkowski and the base manifold of the internal space is conformally Kahler for SU(2) structures, while for SU(3) structures the internal space has to be Einstein-Sasaki and no internal fluxes are allowed. Moreover, we provide a new vacuum with N = 1 supersymmetry and SU(3) structure, where all fluxes are non-zero and the first order differential equations are solved. In the second part, we simply review the methods used to construct one subclass of fluxed-deformed geometry or the so-called "twisted manifold", and the associated 4D effective theory describing these flux vacua. Then by employing (generalized) Scherk-Schwarz reduction, we construct the geometric twisting for Calabi-Yau manifolds of Voisin-Borcea type (K 3 x T2)/ Z2 and study the superpotential in a type IIA orientifold based on this geometry. The twists modify the direct product by fibering the K 3 over T2 while preserving the Z2 involution. As an important application, the Voisin-Borcea class contains T6/( Z2 x Z2 ), the usual setting for intersecting D6 brane model building. Past work in this context considered only those twists inherited

  3. High resolution quantum metrology via quantum interpolation

    NASA Astrophysics Data System (ADS)

    Ajoy, Ashok; Liu, Yixiang; Saha, Kasturi; Marseglia, Luca; Jaskula, Jean-Christophe; Cappellaro, Paola

    2016-05-01

    Nitrogen Vacancy (NV) centers in diamond are a promising platform for quantum metrology - in particular for nanoscale magnetic resonance imaging to determine high resolution structures of single molecules placed outside the diamond. The conventional technique for sensing of external nuclear spins involves monitoring the effects of the target nuclear spins on the NV center coherence under dynamical decoupling (the CPMG/XY8 pulse sequence). However, the nuclear spin affects the NV coherence only at precise free evolution times - and finite timing resolution set by hardware often severely limits the sensitivity and resolution of the method. In this work, we overcome this timing resolution barrier by developing a technique to supersample the metrology signal by effectively implementing a quantum interpolation of the spin system dynamics. This method will enable spin sensing at high magnetic fields and high repetition rate, allowing significant improvements in sensitivity and spectral resolution. We experimentally demonstrate a resolution boost by over a factor of 100 for spin sensing and AC magnetometry. The method is shown to be robust, versatile to sensing normal and spurious signal harmonics, and ultimately limited in resolution only by the number of pulses that can be applied.

  4. Waveform control pulse magnetization for HTS bulk magnet

    NASA Astrophysics Data System (ADS)

    Ida, Tetsuya; Shigeuchi, Koji; Okuda, Sayo; Watasaki, Masahiro; Izumi, Mitsuru

    2016-03-01

    For the past 10 years, we have studied high-temperature superconducting (HTS) bulk magnets for use in electromagnetic rotating machines. If the magnetic field effectively magnetizes the HTS bulk, then the size of the motor and generator can be reduced without a reduction in output. We showed that the melt-textured Gd-Ba-Cu-O HTS bulk effectively traps a high magnetic field using waveform control pulse magnetization (WCPM). WCPM makes it possible to generate any pulsed magnetic field waveform by appropriately changing the duty ratio of the pulse width modulation. By chopping so that the pulsed magnetic field has a period of about 1ms, the WCPM technology enables active control of the rise time and suppresses magnetic flux motion that decreases magnetization efficiency. This method is also useful for any HTS bulk magnet, and the high magnetic flux density is trapped in the HTS bulk by a single pulse magnetic field. We developed a magnetizer that has a feedback system from the penetrated magnetic flux density to realize WCPM. In this research, using only a single pulse magnetic field of WCPM method at 77K, an HTS bulk with a 45mm diameter and 19mm thickness trapped a maximum magnetic field of 1.63T, which is more than 90% of the trapped magnetic flux density by FC magnetization. This result suggests that the pulse magnetizing method can replace the conventional field-cooled method and promote the practical use of HTS magnets for electromagnetic power applications.

  5. Repeated interactions in open quantum systems

    SciTech Connect

    Bruneau, Laurent; Joye, Alain; Merkli, Marco

    2014-07-15

    Analyzing the dynamics of open quantum systems has a long history in mathematics and physics. Depending on the system at hand, basic physical phenomena that one would like to explain are, for example, convergence to equilibrium, the dynamics of quantum coherences (decoherence) and quantum correlations (entanglement), or the emergence of heat and particle fluxes in non-equilibrium situations. From the mathematical physics perspective, one of the main challenges is to derive the irreversible dynamics of the open system, starting from a unitary dynamics of the system and its environment. The repeated interactions systems considered in these notes are models of non-equilibrium quantum statistical mechanics. They are relevant in quantum optics, and more generally, serve as a relatively well treatable approximation of a more difficult quantum dynamics. In particular, the repeated interaction models allow to determine the large time (stationary) asymptotics of quantum systems out of equilibrium.

  6. Quantum Radiation Reaction: From Interference to Incoherence

    NASA Astrophysics Data System (ADS)

    Dinu, Victor; Harvey, Chris; Ilderton, Anton; Marklund, Mattias; Torgrimsson, Greger

    2016-01-01

    We investigate quantum radiation reaction in laser-electron interactions across different energy and intensity regimes. Using a fully quantum approach which also accounts exactly for the effect of the strong laser pulse on the electron motion, we identify in particular a regime in which radiation reaction is dominated by quantum interference. We find signatures of quantum radiation reaction in the electron spectra which have no classical analogue and which cannot be captured by the incoherent approximations typically used in the high-intensity regime. These signatures are measurable with presently available laser and accelerator technology.

  7. Quantum robots and quantum computers

    SciTech Connect

    Benioff, P.

    1998-07-01

    Validation of a presumably universal theory, such as quantum mechanics, requires a quantum mechanical description of systems that carry out theoretical calculations and systems that carry out experiments. The description of quantum computers is under active development. No description of systems to carry out experiments has been given. A small step in this direction is taken here by giving a description of quantum robots as mobile systems with on board quantum computers that interact with different environments. Some properties of these systems are discussed. A specific model based on the literature descriptions of quantum Turing machines is presented.

  8. Quantum hair and quantum gravity

    SciTech Connect

    Coleman, S. ); Krauss, L.M. ); Preskill, J. ); Wilczek, F. )

    1992-01-01

    A black hole may carry quantum numbers that are not associated with massless gauge fields, contrary to the spirit of the 'no-hair' theorems. The 'quantum hair' is invisible in the classical limit, but measurable via quantum interference experiments. Quantum hair alters the temperature of the radiation emitted by a black hole. It also induces non-zero expectation values for fields outside the event horizon; these expectation values are non-perturbative in [Dirac h], and decay exponentially far from the hole. The existence of quantum hair demonstrates that a black hole can have an intricate quantum-mechanical structure that is completely missed by standard semiclassical theory.

  9. Quantum Darwinism

    SciTech Connect

    Zurek, Wojciech H

    2008-01-01

    Quantum Darwinism - proliferation, in the environment, of multiple records of selected states of the system (its information-theoretic progeny) - explains how quantum fragility of individual state can lead to classical robustness of their multitude.

  10. Quantum Orbifolds

    NASA Astrophysics Data System (ADS)

    Harju, Antti J.

    2016-06-01

    This is a study of orbifold-quotients of quantum groups (quantum orbifolds {Θ } rightrightarrows Gq). These structures have been studied extensively in the case of the quantum S U 2 group. A generalized theory of quantum orbifolds over compact simple and simply connected quantum groups is developed. Associated with a quantum orbifold there is an invariant subalgebra and a crossed product algebra. For each spin quantum orbifold, there is a unitary equivalence class of Dirac spectral triples over the invariant subalgebra, and for each effective spin quantum orbifold associated with a finite group action, there is a unitary equivalence class of Dirac spectral triples over the crossed product algebra. A Hopf-equivariant Fredholm index problem is studied as an application.

  11. Quantum memristors

    DOE PAGESBeta

    Pfeiffer, P.; Egusquiza, I. L.; Di Ventra, M.; Sanz, M.; Solano, E.

    2016-07-06

    Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantummore » regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. As a result, the proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems.« less

  12. Video Meteor Fluxes

    NASA Technical Reports Server (NTRS)

    Campbell-Brown, M. D.; Braid, D.

    2011-01-01

    The flux of meteoroids, or number of meteoroids per unit area per unit time, is critical for calibrating models of meteoroid stream formation and for estimating the hazard to spacecraft from shower and sporadic meteors. Although observations of meteors in the millimetre to centimetre size range are common, flux measurements (particularly for sporadic meteors, which make up the majority of meteoroid flux) are less so. It is necessary to know the collecting area and collection time for a given set of observations, and to correct for observing biases and the sensitivity of the system. Previous measurements of sporadic fluxes are summarized in Figure 1; the values are given as a total number of meteoroids striking the earth in one year to a given limiting mass. The Gr n et al. (1985) flux model is included in the figure for reference. Fluxes for sporadic meteoroids impacting the Earth have been calculated for objects in the centimeter size range using Super-Schmidt observations (Hawkins & Upton, 1958); this study used about 300 meteors, and used only the physical area of overlap of the cameras at 90 km to calculate the flux, corrected for angular speed of meteors, since a large angular speed reduces the maximum brightness of the meteor on the film, and radiant elevation, which takes into account the geometric reduction in flux when the meteors are not perpendicular to the horizontal. They bring up corrections for both partial trails (which tends to increase the collecting area) and incomplete overlap at heights other than 90 km (which tends to decrease it) as effects that will affect the flux, but estimated that the two effects cancelled one another. Halliday et al. (1984) calculated the flux of meteorite-dropping fireballs with fragment masses greater than 50 g, over the physical area of sky accessible to the MORP fireball cameras, counting only observations in clear weather. In the micron size range, LDEF measurements of small craters on spacecraft have been used to

  13. Effect of Orbital Angular Momentum on Nondiffracting Ultrashort Optical Pulses

    NASA Astrophysics Data System (ADS)

    Ornigotti, Marco; Conti, Claudio; Szameit, Alexander

    2015-09-01

    We introduce a new class of nondiffracting optical pulses possessing orbital angular momentum. By generalizing the X -wave solution of the Maxwell equation, we discover the coupling between angular momentum and the temporal degrees of freedom of ultrashort pulses. The spatial twist of propagation invariant light pulse turns out to be directly related to the number of optical cycles. Our results may trigger the development of novel multilevel classical and quantum transmission channels free of dispersion and diffraction. They may also find application in the manipulation of nanostructured objects by ultrashort pulses and for novel approaches to the spatiotemporal measurements in ultrafast photonics.

  14. Effect of Orbital Angular Momentum on Nondiffracting Ultrashort Optical Pulses.

    PubMed

    Ornigotti, Marco; Conti, Claudio; Szameit, Alexander

    2015-09-01

    We introduce a new class of nondiffracting optical pulses possessing orbital angular momentum. By generalizing the X-wave solution of the Maxwell equation, we discover the coupling between angular momentum and the temporal degrees of freedom of ultrashort pulses. The spatial twist of propagation invariant light pulse turns out to be directly related to the number of optical cycles. Our results may trigger the development of novel multilevel classical and quantum transmission channels free of dispersion and diffraction. They may also find application in the manipulation of nanostructured objects by ultrashort pulses and for novel approaches to the spatiotemporal measurements in ultrafast photonics. PMID:26382668

  15. Theory of pulsed Reaction Yield Detected Magnetic Resonance.

    PubMed

    Nasibulov, Egor A; Kulik, Leonid V; Kaptein, Robert; Ivanov, Konstantin L

    2012-10-14

    We propose pulse sequences for Reaction Yield Detected Magnetic Resonance (RYDMR), which are based on refocusing the zero-quantum coherences in radical pairs by non-selective microwave pulses and using the population of a radical pair singlet spin state as an observable. The new experiments are analogues of existing EPR experiments such as the primary echo, Carr-Purcell, ESEEM, stimulated echo and Mims ENDOR. All pulse sequences are supported by analytical results and numerical calculations. The pulse sequences can be used for more efficient and highly detailed characterization of intermediates of chemical reactions and charge carriers in organic semiconductors. PMID:22930135

  16. LCLS Spectral Flux Viewer

    Energy Science and Technology Software Center (ESTSC)

    2005-10-25

    This application (FluxViewer) is a tool for displaying spectral flux data for the Linac Coherent Light Source (LCLS). This tool allows the user to view sliced spatial and energy distributions of the photons selected for specific energies and positions transverse to the beam axis.

  17. Long pulse production from short pulses

    DOEpatents

    Toeppen, J.S.

    1994-08-02

    A method of producing a long output pulse from a short pump pulse is disclosed, using an elongated amplified fiber having a doped core that provides an amplifying medium for light of one color when driven into an excited state by light of a shorter wavelength and a surrounding cladding. A seed beam of the longer wavelength is injected into the core at one end of the fiber and a pump pulse of the shorter wavelength is injected into the cladding at the other end of the fiber. The counter-propagating seed beam and pump pulse will produce an amplified output pulse having a time duration equal to twice the transit time of the pump pulse through the fiber plus the length of the pump pulse. 3 figs.

  18. Long pulse production from short pulses

    DOEpatents

    Toeppen, John S.

    1994-01-01

    A method of producing a long output pulse (SA) from a short pump pulse (P), using an elongated amplified fiber (11) having a doped core (12) that provides an amplifying medium for light of one color when driven into an excited state by light of a shorter wavelength and a surrounding cladding 13. A seed beam (S) of the longer wavelength is injected into the core (12) at one end of the fiber (11) and a pump pulse (P) of the shorter wavelength is injected into the cladding (13) at the other end of the fiber (11). The counter-propagating seed beam (S) and pump pulse (P) will produce an amplified output pulse (SA) having a time duration equal to twice the transit time of the pump pulse (P) through the fiber (11) plus the length of the pump pulse (P).

  19. Entanglement-assisted electron microscopy based on a flux qubit

    SciTech Connect

    Okamoto, Hiroshi; Nagatani, Yukinori

    2014-02-10

    A notorious problem in high-resolution biological electron microscopy is radiation damage caused by probe electrons. Hence, acquisition of data with minimal number of electrons is of critical importance. Quantum approaches may represent the only way to improve the resolution in this context, but all proposed schemes to date demand delicate control of the electron beam in highly unconventional electron optics. Here we propose a scheme that involves a flux qubit based on a radio-frequency superconducting quantum interference device, inserted in a transmission electron microscope. The scheme significantly improves the prospect of realizing a quantum-enhanced electron microscope for radiation-sensitive specimens.

  20. Kicking atoms with finite duration pulses

    NASA Astrophysics Data System (ADS)

    Fekete, Julia; Chai, Shijie; Daszuta, Boris; Andersen, Mikkel F.

    2016-05-01

    The atom optics delta-kicked particle is a paradigmatic system for experimental studies of quantum chaos and classical-quantum correspondence. It consists of a cloud of laser cooled atoms exposed to a periodically pulsed standing wave of far off-resonant laser light. A purely quantum phenomena in such systems are quantum resonances which transfers the atoms into a coherent superposition of largely separated momentum states. Using such large momentum transfer ``beamsplitters'' in atom interferometers may have applications in high precision metrology. The growth in momentum separation cannot be maintained indefinitely due to finite laser power. The largest momentum transfer is achieved by violating the usual delta-kick assumption. Therefore we explore the behavior of the atom optics kicked particle with finite pulse duration. We have developed a semi-classical model which shows good agreement with the full quantum description as well as our experiments. Furthermore we have found a simple scaling law that helps to identify optimal parameters for an atom interferometer. We verify this by measurements of the ``Talbot time'' (a measurement of h/m) which together with other well-known constants constitute a measurement of the fine structure constant.