Single Quantum Level Electron Turnstile
NASA Astrophysics Data System (ADS)
van Zanten, D. M. T.; Basko, D. M.; Khaymovich, I. M.; Pekola, J. P.; Courtois, H.; Winkelmann, C. B.
2016-04-01
We report on the realization of a single-electron source, where current is transported through a single-level quantum dot (Q ) tunnel coupled to two superconducting leads (S ). When driven with an ac gate voltage, the experiment demonstrates electron turnstile operation. Compared to the more conventional superconductor-normal-metal-superconductor turnstile, our superconductor-quantum-dot-superconductor device presents a number of novel properties, including higher immunity to the unavoidable presence of nonequilibrium quasiparticles in superconducting leads. Moreover, we demonstrate its ability to deliver electrons with a very narrow energy distribution.
Single Quantum Level Electron Turnstile.
van Zanten, D M T; Basko, D M; Khaymovich, I M; Pekola, J P; Courtois, H; Winkelmann, C B
2016-04-22
We report on the realization of a single-electron source, where current is transported through a single-level quantum dot (Q) tunnel coupled to two superconducting leads (S). When driven with an ac gate voltage, the experiment demonstrates electron turnstile operation. Compared to the more conventional superconductor-normal-metal-superconductor turnstile, our superconductor-quantum-dot-superconductor device presents a number of novel properties, including higher immunity to the unavoidable presence of nonequilibrium quasiparticles in superconducting leads. Moreover, we demonstrate its ability to deliver electrons with a very narrow energy distribution. PMID:27152817
Quantum dissonance and deterministic quantum computation with a single qubit
NASA Astrophysics Data System (ADS)
Ali, Mazhar
2014-11-01
Mixed state quantum computation can perform certain tasks which are believed to be efficiently intractable on a classical computer. For a specific model of mixed state quantum computation, namely, deterministic quantum computation with a single qubit (DQC1), recent investigations suggest that quantum correlations other than entanglement might be responsible for the power of DQC1 model. However, strictly speaking, the role of entanglement in this model of computation was not entirely clear. We provide conclusive evidence that there are instances where quantum entanglement is not present in any part of this model, nevertheless we have advantage over classical computation. This establishes the fact that quantum dissonance (a kind of quantum correlations) present in fully separable (FS) states provide power to DQC1 model.
Single-Atom Single-Photon Quantum Interface
NASA Astrophysics Data System (ADS)
Moehring, David; Bochmann, Joerg; Muecke, Martin; Specht, Holger; Weber, Bernhard; Wilk, Tatjana; Rempe, Gerhard
2008-05-01
By combining atom trapping techniques and cavity cooling schemes we are able to trap a single neutral atom inside a high-finesse cavity for several tens of seconds. We show that our coupled atom-cavity system can be used to generate single photons in a controlled way. With our long trapping times and high single-photon production efficiency, the non-classical properties of the emitted light can be shown in the photon correlations of a single atom. In a similar atom-cavity setup, we investigate the interface between atoms and photons by entangling a single atom with a single photon emitted into the cavity and by further mapping the quantum state of the atom onto a second single photon. These schemes are intrinsically deterministic and establish the basic element required to realize a distributed quantum network with individual atoms at rest as quantum memories and single flying photons as quantum messengers. This work was supported by the Deutsche Forschungsgemeinschaft, and the European Union SCALA and CONQUEST programs. D. L. M. acknowledges support from the Alexander von Humboldt Foundation.
Single-qubit optical quantum fingerprinting.
Horn, Rolf T; Babichev, S A; Marzlin, Karl-Peter; Lvovsky, A I; Sanders, Barry C
2005-10-01
We analyze and demonstrate the feasibility and superiority of linear optical single-qubit fingerprinting over its classical counterpart. For one-qubit fingerprinting of two-bit messages, we prepare "tetrahedral" qubit states experimentally and show that they meet the requirements for quantum fingerprinting to exceed the classical capability. We prove that shared entanglement permits 100% reliable quantum fingerprinting, which will outperform classical fingerprinting even with arbitrary amounts of shared randomness. PMID:16241707
Quantum Clock Synchronization with a Single Qudit
Tavakoli, Armin; Cabello, Adán; Żukowski, Marek; Bourennane, Mohamed
2015-01-01
Clock synchronization for nonfaulty processes in multiprocess networks is indispensable for a variety of technologies. A reliable system must be able to resynchronize the nonfaulty processes upon some components failing causing the distribution of incorrect or conflicting information in the network. The task of synchronizing such networks is related to Byzantine agreement (BA), which can classically be solved using recursive algorithms if and only if less than one-third of the processes are faulty. Here we introduce a nonrecursive quantum algorithm, based on a quantum solution of the detectable BA, which achieves clock synchronization in the presence of arbitrary many faulty processes by using only a single quantum system. PMID:25613754
Mechanical analysis of photo-electricity measure equipment shafting in mobile-platform
NASA Astrophysics Data System (ADS)
Jiang, Weiwei; Hu, Hongyi; Tan, Yi; Liu, Ruzhen
2015-02-01
Along with the development of technology, photo-electricity measure equipment has been from ground-fixed to mobile-platform borne, So it is need to mechanical analysis of shafting for adapt movement environment of mobile-platform. First listed three kinds of shafting form, then analysis mechanical station of the foremost component bearing in vertical load, radial load, swing load station, last work out the formulas, which was the theory for the shafting design in mobile-platforms photo-electricity equipment.
Single Ion Quantum Lock-In Amplifier
NASA Astrophysics Data System (ADS)
Kotler, Shlomi; Akerman, Nitzan; Glickman, Yinnon; Keselman, Anna; Ozeri, Roee
2011-05-01
Invented by Dicke, the lock-in measurement is a phase-sensitive detection scheme that can extract a signal with a known carrier frequency from an extremely noisy environment. Here we report on the implementation of a quantum analog to the classical lock- in amplifier. All the lock-in operations: modulation, detection and mixing, are performed via the application of non-commuting quantum operators on the electronic spin state of a single trapped Sr+ ion. We increase its sensitivity to external fields while extending phase coherence by three orders of magnitude, to more than one second. With this technique we measure magnetic fields with sensitivity of 25 pT /√{ Hz } , and light shifts with an uncertainty below 140 mHz after 1320 seconds of averaging. These sensitivities are limited by quantum projection noise and, to our knowledge, are more than two orders of magnitude better than with other single-spin probe technologies. As a first application we perform light shift spectroscopy of a narrow optical quadruple transition. We remark that the quantum lock-in technique is generic and can potentially enhance the sensitivity of any quantum sensor. (http://arxiv.org/abs/1101.4885)
Quantum propagation in single mode fiber
NASA Technical Reports Server (NTRS)
Joneckis, Lance G.; Shapiro, Jeffrey H.
1994-01-01
This paper presents a theory for quantum light propagation in a single-mode fiber which includes the effects of the Kerr nonlinearity, group-velocity dispersion, and linear loss. The theory reproduces the results of classical self-phase modulation, quantum four-wave mixing, and classical solution physics, within their respective regions of validity. It demonstrates the crucial role played by the Kerr-effect material time constant, in limiting the quantum phase shifts caused by the broadband zero-point fluctuations that accompany any quantized input field. Operator moment equations - approximated, numerically, via a terminated cumulant expansion - are used to obtain results for homodyne-measurement noise spectra when dispersion is negligible. More complicated forms of these equations can be used to incorporate dispersion into the noise calculations.
Transform-limited single photons from a single quantum dot
Kuhlmann, Andreas V.; Prechtel, Jonathan H.; Houel, Julien; Ludwig, Arne; Reuter, Dirk; Wieck, Andreas D.; Warburton, Richard J.
2015-01-01
Developing a quantum photonics network requires a source of very-high-fidelity single photons. An outstanding challenge is to produce a transform-limited single-photon emitter to guarantee that single photons emitted far apart in the time domain are truly indistinguishable. This is particularly difficult in the solid-state as the complex environment is the source of noise over a wide bandwidth. A quantum dot is a robust, fast, bright and narrow-linewidth emitter of single photons; layer-by-layer growth and subsequent nano-fabrication allow the electronic and photonic states to be engineered. This represents a set of features not shared by any other emitter but transform-limited linewidths have been elusive. Here, we report transform-limited linewidths measured on second timescales, primarily on the neutral exciton but also on the charged exciton close to saturation. The key feature is control of the nuclear spins, which dominate the exciton dephasing via the Overhauser field. PMID:26348157
Single mode terahertz quantum cascade amplifier
Ren, Y. Wallis, R.; Shah, Y. D.; Jessop, D. S.; Degl'Innocenti, R.; Klimont, A.; Kamboj, V.; Beere, H. E.; Ritchie, D. A.
2014-10-06
A terahertz (THz) optical amplifier based on a 2.9 THz quantum cascade laser (QCL) structure has been demonstrated. By depositing an antireflective coating on the QCL facet, the laser mirror losses are enhanced to fully suppress the lasing action, creating a THz quantum cascade (QC) amplifier. Terahertz radiation amplification has been obtained, by coupling a separate multi-mode THz QCL of the same active region design to the QC amplifier. A bare cavity gain is achieved and shows excellent agreement with the lasing spectrum from the original QCL without the antireflective coating. Furthermore, a maximum optical gain of ∼30 dB with single-mode radiation output is demonstrated.
Single-mode tapered quantum cascade lasers
NASA Astrophysics Data System (ADS)
Rauter, Patrick; Menzel, Stefan; Gokden, B.; K. Goyal, Anish; Wang, Christine A.; Sanchez, Antonio; Turner, George; Capasso, Federico
2013-05-01
We demonstrate tapered quantum cascade lasers monolithically integrated with a distributed Bragg reflector acting as both a wavelength-selective back mirror and a transverse mode filter. Each of the 14 devices operates at a different wavelength between 9.2 and 9.7 μm, where nine devices feature single-mode operation at peak powers between 0.3 and 1.6 W at room temperature. High output power and excellent beam quality with peak brightness values up to 1.6 MW cm-2 sr-1 render these two-terminal devices highly suitable for stand-off spectroscopy applications.
Application of fuzzy evidence theory in a photo-electric measurement system
NASA Astrophysics Data System (ADS)
Song, Jianxun; Xiong, Maotao; Zhang, Jin; Wu, Qinzhang
2009-05-01
The photo-electric measurement system is a kind of high-precision measurement system for trajectory parameters and object identity parameters, and it can acquire the image information of flying objects by CCD camera. Due to subject to some kinds of reasons, the feature information of image is not integrated and imprecise, and it has uncertainty and fuzzy in some degree. The Dempster-Shafer evidence theory is an important approach of uncertainty reasoning. With evidences fused, the uncertainty of the feature information of the object is declined gradually by Dempster combination rule, so it can achieve the aim of object detection and object recognition. The conception of fuzzy mass is expanded in the way of the relation of absolute membership on the basis of normal mass conception. The fuzzy theory is very suitable for the description and processing of uncertainty to evidences in D-S evidence theory, so the Basic Probability Assignment Function (BPAF) of D-S evidence theory can be acquired according to fuzzy theory, and it resolves crucial problem in D-S evidence theory. It is shown that data fusion method of fuzzy evidence theory can deal with uncertainty and the fuzzy of photo-electric measurement system according to the analysis of theory and the result of experimentation, and it has a bright future in photo-electric measurement systems.
Study on the technology of mutual alignment based on the four-quadrant photo electric detector
NASA Astrophysics Data System (ADS)
Hu, Ya-bin; Wang, Miao
2015-11-01
Panoramic stereo cameras and laser radars have their own coordinate system in the dynamic spatial sensing area and they have to determine the position relationship between each other through joint calibration. As using the traditional technology of mutual alignment based on the telescope cross wire is tedious and requires high operating skills, a new method of mutual alignment using lasers and four-quadrant photo electric detectors is provided after analyzing the working principle of four-quadrant photo electric detectors. Firstly make the laser beam irradiate the active area of the four-quadrant photo electric detector through coarse aiming. Then the center of a light spot offset relative to the center of the active area can be obtained according to the output voltage of four quadrants. The pose of two instruments can be adjusted properly to realize mutual alignment. The experimental results indicate that the alignment accuracy of four-quadrant detectors can meet the requirements of mutual alignment, which provides a new idea for joint calibration.
Spectroscopy of Single Free Standing Quantum Wells
Williams, M D; Hollars, C W; Huser, T; Jallow, N; Cochran, A; Bryant, R
2006-03-14
We investigated the interaction of quantum confined exciton states GaAs quantum wells with native surface states. Single molecule photoluminescence (PL) spectroscopy, developed by T. Huser at LLNL was used to probe the unique bare quantum wells in the free standing quantum well structure. The latter was developed by the M. D. Williams at Clark Atlanta University. The goals of the project during this budget cycle were to procure samples containing GaAs free standing QWs, identify suitable regions for PL analysis at Lawrence Livermore, analyze the structures at room temperature and at liquid nitrogen temperatures. The specific regions of interest on the sample structures were identified by scanning electron microscopy at Clark Atlanta prior to transport to LLNL. Previous attempts at other facilities using NSOM, cathodoluminescence, and conventional PL showed little luminescence activity at room temperature from the 200 {angstrom} thick wells. This suggested either excess recombination due to surface states in the quantum well region or insufficient absorption length for photoluminescence. The literature suggested that the effect of the defects could be eliminated by reducing the sample temperature below their associated activation energies. In our previous subcontract work with LLNL, a significant amount of effort was expended to modify the apparatus to allow low temperature measurements. The modifications were not successful and we concluded that in order to do the measurements at low temperature we would need to purchase a commercial optical cryostat to get reliable results. Ms. Rochelle Bryant worked during the summer as an intern at LLNL on the project under the supervision of C. Hollars and in collaboration with T. Huser and found that PL emission could be obtained at room temperature. This was a surprising result as the literature and our experience shows that there is no PL emission from GaAs at room temperature. We speculate that this is due to the small
Universal quantum gates for Single Cooper Pair Box based quantum computing
NASA Technical Reports Server (NTRS)
Echternach, P.; Williams, C. P.; Dultz, S. C.; Braunstein, S.; Dowling, J. P.
2000-01-01
We describe a method for achieving arbitrary 1-qubit gates and controlled-NOT gates within the context of the Single Cooper Pair Box (SCB) approach to quantum computing. Such gates are sufficient to support universal quantum computation.
Single-photon quantum router with multiple output ports.
Yan, Wei-Bin; Fan, Heng
2014-01-01
The routing capability is a requisite in quantum network. Although the quantum routing of signals has been investigated in various systems both in theory and experiment, the general form of quantum routing with many output terminals still needs to be explored. Here we propose a scheme to achieve the multi-channel quantum routing of the single photons in a waveguide-emitter system. The channels are composed by the waveguides and are connected by intermediate two-level emitters. By adjusting the intermediate emitters, the output channels of the input single photons can be controlled. This is demonstrated in the cases of one output channel, two output channels and the generic N output channels. The results show that the multi-channel quantum routing of single photons can be well achieved in the proposed system. This offers a scheme for the experimental realization of general quantum routing of single photons. PMID:24769619
Quantum nanophotonics: Controlling a photon with a single spin
NASA Astrophysics Data System (ADS)
Waks, Edo
The implementation of quantum network and distributive quantum computation replies on strong interactions between stationary matter qubits and flying photons. The spin of a single electron confined in a quantum dot is considered as a promising matter qubit as it possesses microsecond coherence time and allows picosecond timescale control using optical pulses. The quantum dot spin can also interact with a photon by controlling the optical response of a strongly coupled cavity. In this talk I will discuss our recent work on an experimental realization of a spin-photon quantum phase switch using a single spin in a quantum dot strongly coupled to a photonic crystal cavity. We show large modulation of the cavity reflection spectrum by manipulating the spin states of the quantum dot, which enables us to control the quantum state of a reflected photon. We also show the complementary effect where the presence of a single photon switches the quantum state of the spin. The reported spin-photon quantum phase operation can switch spin or photon states in picoseconds timescale, representing an important step towards GHz semiconductor based quantum logic devices on-a-chip and solid-state implementations of quantum networks. Shuo Sun, Hyochul Kim, Glenn Solomon, co-authors.
Quantum interference of independently generated telecom-band single photons
Patel, Monika; Altepeter, Joseph B.; Huang, Yu-Ping; Oza, Neal N.; Kumar, Prem
2014-12-04
We report on high-visibility quantum interference of independently generated telecom O-band (1310 nm) single photons using standard single-mode fibers. The experimental data are shown to agree well with the results of simulations using a comprehensive quantum multimode theory without the need for any fitting parameter.
Single-electron Spin Resonance in a Quadruple Quantum Dot
Otsuka, Tomohiro; Nakajima, Takashi; Delbecq, Matthieu R.; Amaha, Shinichi; Yoneda, Jun; Takeda, Kenta; Allison, Giles; Ito, Takumi; Sugawara, Retsu; Noiri, Akito; Ludwig, Arne; Wieck, Andreas D.; Tarucha, Seigo
2016-01-01
Electron spins in semiconductor quantum dots are good candidates of quantum bits for quantum information processing. Basic operations of the qubit have been realized in recent years: initialization, manipulation of single spins, two qubit entanglement operations, and readout. Now it becomes crucial to demonstrate scalability of this architecture by conducting spin operations on a scaled up system. Here, we demonstrate single-electron spin resonance in a quadruple quantum dot. A few-electron quadruple quantum dot is formed within a magnetic field gradient created by a micro-magnet. We oscillate the wave functions of the electrons in the quantum dots by applying microwave voltages and this induces electron spin resonance. The resonance energies of the four quantum dots are slightly different because of the stray field created by the micro-magnet and therefore frequency-resolved addressable control of each electron spin resonance is possible. PMID:27550534
Single-electron Spin Resonance in a Quadruple Quantum Dot.
Otsuka, Tomohiro; Nakajima, Takashi; Delbecq, Matthieu R; Amaha, Shinichi; Yoneda, Jun; Takeda, Kenta; Allison, Giles; Ito, Takumi; Sugawara, Retsu; Noiri, Akito; Ludwig, Arne; Wieck, Andreas D; Tarucha, Seigo
2016-01-01
Electron spins in semiconductor quantum dots are good candidates of quantum bits for quantum information processing. Basic operations of the qubit have been realized in recent years: initialization, manipulation of single spins, two qubit entanglement operations, and readout. Now it becomes crucial to demonstrate scalability of this architecture by conducting spin operations on a scaled up system. Here, we demonstrate single-electron spin resonance in a quadruple quantum dot. A few-electron quadruple quantum dot is formed within a magnetic field gradient created by a micro-magnet. We oscillate the wave functions of the electrons in the quantum dots by applying microwave voltages and this induces electron spin resonance. The resonance energies of the four quantum dots are slightly different because of the stray field created by the micro-magnet and therefore frequency-resolved addressable control of each electron spin resonance is possible. PMID:27550534
Photon Cascade from a Single Crystal Phase Nanowire Quantum Dot.
Bouwes Bavinck, Maaike; Jöns, Klaus D; Zieliński, Michal; Patriarche, Gilles; Harmand, Jean-Christophe; Akopian, Nika; Zwiller, Val
2016-02-10
We report the first comprehensive experimental and theoretical study of the optical properties of single crystal phase quantum dots in InP nanowires. Crystal phase quantum dots are defined by a transition in the crystallographic lattice between zinc blende and wurtzite segments and therefore offer unprecedented potential to be controlled with atomic layer accuracy without random alloying. We show for the first time that crystal phase quantum dots are a source of pure single-photons and cascaded photon-pairs from type II transitions with excellent optical properties in terms of intensity and line width. We notice that the emission spectra consist often of two peaks close in energy, which we explain with a comprehensive theory showing that the symmetry of the system plays a crucial role for the hole levels forming hybridized orbitals. Our results state that crystal phase quantum dots have promising quantum optical properties for single photon application and quantum optics. PMID:26806321
Dissipation-enabled efficient excitation transfer from a single photon to a single quantum emitter
NASA Astrophysics Data System (ADS)
Trautmann, N.; Alber, G.
2016-05-01
We propose a scheme for triggering a dissipation-dominated highly efficient excitation transfer from a single-photon wave packet to a single quantum emitter. This single-photon-induced optical pumping turns dominant dissipative processes, such as spontaneous photon emission by the emitter or cavity decay, into valuable tools for quantum information processing and quantum communication. It works for an arbitrarily shaped single-photon wave packet with sufficiently small bandwidth provided a matching condition is satisfied which balances the dissipative rates involved. Our scheme does not require additional laser pulses or quantum feedback and does not rely on high finesse optical resonators. In particular, it can be used to enhance significantly the coupling of a single photon to a single quantum emitter implanted in a one-dimensional waveguide or even in a free space scenario. We demonstrate the usefulness of our scheme for building a deterministic quantum memory and a deterministic frequency converter between photonic qubits of different wavelengths.
Nanophotonic quantum phase switch with a single atom.
Tiecke, T G; Thompson, J D; de Leon, N P; Liu, L R; Vuletić, V; Lukin, M D
2014-04-10
By analogy to transistors in classical electronic circuits, quantum optical switches are important elements of quantum circuits and quantum networks. Operated at the fundamental limit where a single quantum of light or matter controls another field or material system, such a switch may enable applications such as long-distance quantum communication, distributed quantum information processing and metrology, and the exploration of novel quantum states of matter. Here, by strongly coupling a photon to a single atom trapped in the near field of a nanoscale photonic crystal cavity, we realize a system in which a single atom switches the phase of a photon and a single photon modifies the atom's phase. We experimentally demonstrate an atom-induced optical phase shift that is nonlinear at the two-photon level, a photon number router that separates individual photons and photon pairs into different output modes, and a single-photon switch in which a single 'gate' photon controls the propagation of a subsequent probe field. These techniques pave the way to integrated quantum nanophotonic networks involving multiple atomic nodes connected by guided light. PMID:24717513
Single-Molecule Tracking in Living Cells Using Single Quantum Dot Applications
Baba, Koichi; Nishida, Kohji
2012-01-01
Revealing the behavior of single molecules in living cells is very useful for understanding cellular events. Quantum dot probes are particularly promising tools for revealing how biological events occur at the single molecule level both in vitro and in vivo. In this review, we will introduce how single quantum dot applications are used for single molecule tracking. We will discuss how single quantum dot tracking has been used in several examples of complex biological processes, including membrane dynamics, neuronal function, selective transport mechanisms of the nuclear pore complex, and in vivo real-time observation. We also briefly discuss the prospects for single molecule tracking using advanced probes. PMID:22896768
Chapter 2 A Single Quantum System
NASA Astrophysics Data System (ADS)
Toschek, Peter E.
The evolution of quantum mechanics has followed the critical analysis of "gedanken" experiments. Many of these concrete speculations can become implemented today in the laboratory--thanks to now available techniques. A key experiment is concerned with the time evolution of a quantum system under repeated or continuing observation. Here, three problems overlap: (1) The microphysical measurement by a macroscopic device, (2) the system's temporal evolution, and (3) the emergence of macroscopic reality out of the microcosmos. A well-known calculation shows the evolution of a quantum system being slowed down, or even obstructed, when the system is merely observed. An experiment designed to demonstrate this "quantum Zeno effect" and performed in the late eighties on an ensemble of identical atomic ions confirmed its quantum description, but turned out inconclusive with respect to the very origin of the impediment of evolution. During the past years, experiments on individual electrodynamically stored and laser-cooled ions have been performed that unequivocally demonstrate the observed system's quantum evolution being impeded. Strategy and results exclude any physical reaction on the measured object, but reveal the effect of the gain of information as put forward by the particular correlation of the ion state with the detected signal. They shed light on the process of measurement as well as on the quantum evolution and allow an epistemological interpretation.
Quantum-dot-spin single-photon interface.
Yilmaz, S T; Fallahi, P; Imamoğlu, A
2010-07-16
Using background-free detection of spin-state-dependent resonance fluorescence from a single-electron charged quantum dot with an efficiency of 0.1%, we realize a classical single spin-photon interface where the detection of a scattered photon with 300 ps time resolution projects the quantum dot spin to a definite spin eigenstate with fidelity exceeding 99%. The bunching of resonantly scattered photons reveals information about electron spin dynamics. High-fidelity fast spin-state initialization heralded by a single photon enables the realization of quantum information processing tasks such as nondeterministic distant spin entanglement. Given that we could suppress the measurement backaction to well below the natural spin-flip rate, realization of a quantum nondemolition measurement of a single spin could be achieved by increasing the fluorescence collection efficiency by a factor exceeding 10 using a photonic nanostructure. PMID:20867763
Optical levitation of a microdroplet containing a single quantum dot.
Minowa, Yosuke; Kawai, Ryoichi; Ashida, Masaaki
2015-03-15
We demonstrate the optical levitation or trapping in helium gas of a single quantum dot (QD) within a liquid droplet. Bright single photon emission from the levitated QD in the droplet was observed for more than 200 s. The observed photon count rates are consistent with the value theoretically estimated from the two-photon-action cross section. This Letter presents the realization of an optically levitated solid-state quantum emitter. PMID:25768143
Signatures of single quantum dots in graphene nanoribbons within the quantum Hall regime.
Tóvári, Endre; Makk, Péter; Rickhaus, Peter; Schönenberger, Christian; Csonka, Szabolcs
2016-06-01
We report on the observation of periodic conductance oscillations near quantum Hall plateaus in suspended graphene nanoribbons. They are attributed to single quantum dots that are formed in the narrowest part of the ribbon, in the valleys and hills of a disorder potential. In a wide flake with two gates, a double-dot system's signature has been observed. Electrostatic confinement is enabled in single-layer graphene due to the gaps that are formed between the Landau levels, suggesting a way to create gate-defined quantum dots that can be accessed with quantum Hall edge states. PMID:27198562
Certifying single-system steering for quantum-information processing
NASA Astrophysics Data System (ADS)
Li, Che-Ming; Chen, Yueh-Nan; Lambert, Neill; Chiu, Ching-Yi; Nori, Franco
2015-12-01
Einstein-Podolsky-Rosen (EPR) steering describes how different ensembles of quantum states can be remotely prepared by measuring one particle of an entangled pair. Here, we investigate quantum steering for single quantum d -dimensional systems (qudits) and devise efficient conditions to certify the steerability therein, which we find are applicable both to single-system steering and EPR steering. In the single-system case our steering conditions enable the unambiguous ruling out of generic classical means of mimicking steering. Ruling out "false-steering" scenarios has implications for securing channels against both cloning-based individual attack and coherent attacks when implementing quantum key distribution using qudits. We also show that these steering conditions also have applications in quantum computation, in that they can serve as an efficient criterion for the evaluation of quantum logic gates of arbitrary size. Finally, we describe how the nonlocal EPR variant of these conditions also function as tools for identifying faithful one-way quantum computation, secure entanglement-based quantum communication, and genuine multipartite EPR steering.
Single-Photon Superradiance from a Quantum Dot
NASA Astrophysics Data System (ADS)
Tighineanu, Petru; Daveau, Raphaël S.; Lehmann, Tau B.; Beere, Harvey E.; Ritchie, David A.; Lodahl, Peter; Stobbe, Søren
2016-04-01
We report on the observation of single-photon superradiance from an exciton in a semiconductor quantum dot. The confinement by the quantum dot is strong enough for it to mimic a two-level atom, yet sufficiently weak to ensure superradiance. The electrostatic interaction between the electron and the hole comprising the exciton gives rise to an anharmonic spectrum, which we exploit to prepare the superradiant quantum state deterministically with a laser pulse. We observe a fivefold enhancement of the oscillator strength compared to conventional quantum dots. The enhancement is limited by the base temperature of our cryostat and may lead to oscillator strengths above 1000 from a single quantum emitter at optical frequencies.
Single-Photon Superradiance from a Quantum Dot.
Tighineanu, Petru; Daveau, Raphaël S; Lehmann, Tau B; Beere, Harvey E; Ritchie, David A; Lodahl, Peter; Stobbe, Søren
2016-04-22
We report on the observation of single-photon superradiance from an exciton in a semiconductor quantum dot. The confinement by the quantum dot is strong enough for it to mimic a two-level atom, yet sufficiently weak to ensure superradiance. The electrostatic interaction between the electron and the hole comprising the exciton gives rise to an anharmonic spectrum, which we exploit to prepare the superradiant quantum state deterministically with a laser pulse. We observe a fivefold enhancement of the oscillator strength compared to conventional quantum dots. The enhancement is limited by the base temperature of our cryostat and may lead to oscillator strengths above 1000 from a single quantum emitter at optical frequencies. PMID:27152804
Single-Shot Fault-Tolerant Quantum Error Correction
NASA Astrophysics Data System (ADS)
Bombín, Héctor
2015-07-01
Conventional quantum error correcting codes require multiple rounds of measurements to detect errors with enough confidence in fault-tolerant scenarios. Here, I show that for suitable topological codes, a single round of local measurements is enough. This feature is generic and is related to self-correction and confinement phenomena in the corresponding quantum Hamiltonian model. Three-dimensional gauge color codes exhibit this single-shot feature, which also applies to initialization and gauge fixing. Assuming the time for efficient classical computations to be negligible, this yields a topological fault-tolerant quantum computing scheme where all elementary logical operations can be performed in constant time.
Quantum Logic with Cavity Photons From Single Atoms.
Holleczek, Annemarie; Barter, Oliver; Rubenok, Allison; Dilley, Jerome; Nisbet-Jones, Peter B R; Langfahl-Klabes, Gunnar; Marshall, Graham D; Sparrow, Chris; O'Brien, Jeremy L; Poulios, Konstantinos; Kuhn, Axel; Matthews, Jonathan C F
2016-07-01
We demonstrate quantum logic using narrow linewidth photons that are produced with an a priori nonprobabilistic scheme from a single ^{87}Rb atom strongly coupled to a high-finesse cavity. We use a controlled-not gate integrated into a photonic chip to entangle these photons, and we observe nonclassical correlations between photon detection events separated by periods exceeding the travel time across the chip by 3 orders of magnitude. This enables quantum technology that will use the properties of both narrow-band single photon sources and integrated quantum photonics. PMID:27447506
Quantum Logic with Cavity Photons From Single Atoms
NASA Astrophysics Data System (ADS)
Holleczek, Annemarie; Barter, Oliver; Rubenok, Allison; Dilley, Jerome; Nisbet-Jones, Peter B. R.; Langfahl-Klabes, Gunnar; Marshall, Graham D.; Sparrow, Chris; O'Brien, Jeremy L.; Poulios, Konstantinos; Kuhn, Axel; Matthews, Jonathan C. F.
2016-07-01
We demonstrate quantum logic using narrow linewidth photons that are produced with an a priori nonprobabilistic scheme from a single 87Rb atom strongly coupled to a high-finesse cavity. We use a controlled-not gate integrated into a photonic chip to entangle these photons, and we observe nonclassical correlations between photon detection events separated by periods exceeding the travel time across the chip by 3 orders of magnitude. This enables quantum technology that will use the properties of both narrow-band single photon sources and integrated quantum photonics.
Operating single quantum emitters with a compact Stirling cryocooler
NASA Astrophysics Data System (ADS)
Schlehahn, A.; Krüger, L.; Gschrey, M.; Schulze, J.-H.; Rodt, S.; Strittmatter, A.; Heindel, T.; Reitzenstein, S.
2015-01-01
The development of an easy-to-operate light source emitting single photons has become a major driving force in the emerging field of quantum information technology. Here, we report on the application of a compact and user-friendly Stirling cryocooler in the field of nanophotonics. The Stirling cryocooler is used to operate a single quantum emitter constituted of a semiconductor quantum dot (QD) at a base temperature below 30 K. Proper vibration decoupling of the cryocooler and its surrounding enables free-space micro-photoluminescence spectroscopy to identify and analyze different charge-carrier states within a single quantum dot. As an exemplary application in quantum optics, we perform a Hanbury-Brown and Twiss experiment demonstrating a strong suppression of multi-photon emission events with g(2)(0) < 0.04 from this Stirling-cooled single quantum emitter under continuous wave excitation. Comparative experiments performed on the same quantum dot in a liquid helium (LHe)-flow cryostat show almost identical values of g(2)(0) for both configurations at a given temperature. The results of this proof of principle experiment demonstrate that low-vibration Stirling cryocoolers that have so far been considered exotic to the field of nanophotonics are an attractive alternative to expensive closed-cycle cryostats or LHe-flow cryostats, which could pave the way for the development of high-quality table-top non-classical light sources.
Single and Multi-channel Quantum Dragons from Rectangular Nanotubes
NASA Astrophysics Data System (ADS)
Li, Zhou; Novotny, Mark
2015-03-01
Recently quantum dragons have been discovered theoretically. Quantum dragons are nanostructures with correlated disorder that permit energy-independent total quantum transmission of electrons. Hence the electrical conductance G in a two-terminal measurement should be the conductance quantum G0 = 2e2 / h . The single-band tight banding model is used. An example of a single-channel quantum dragon is a rectangular nanotube with disorder along the direction z of the electron propagation. Quantum dragons are obtained by solving the time-independent Schrödinger equation to obtain the electrical transmission calT as a function of the incoming electron energy E. A quantum dragon has calT (E) =1 for all energies. This work generalizes the solution of the time-independent Schrödinger equation to the case of more than one open channel, and applies the method to nanotubes formed from rectangular lattices. One can envision such single-walled rectangular nanotubes for iron starting from free-standing single-atom-thick Fe membranes which have recently been obtained experimentally. Supported in part by NSF Grant DMR-1206233.
Operating single quantum emitters with a compact Stirling cryocooler
Schlehahn, A.; Krüger, L.; Gschrey, M.; Schulze, J.-H.; Rodt, S.; Strittmatter, A.; Heindel, T. Reitzenstein, S.
2015-01-15
The development of an easy-to-operate light source emitting single photons has become a major driving force in the emerging field of quantum information technology. Here, we report on the application of a compact and user-friendly Stirling cryocooler in the field of nanophotonics. The Stirling cryocooler is used to operate a single quantum emitter constituted of a semiconductor quantum dot (QD) at a base temperature below 30 K. Proper vibration decoupling of the cryocooler and its surrounding enables free-space micro-photoluminescence spectroscopy to identify and analyze different charge-carrier states within a single quantum dot. As an exemplary application in quantum optics, we perform a Hanbury-Brown and Twiss experiment demonstrating a strong suppression of multi-photon emission events with g{sup (2)}(0) < 0.04 from this Stirling-cooled single quantum emitter under continuous wave excitation. Comparative experiments performed on the same quantum dot in a liquid helium (LHe)-flow cryostat show almost identical values of g{sup (2)}(0) for both configurations at a given temperature. The results of this proof of principle experiment demonstrate that low-vibration Stirling cryocoolers that have so far been considered exotic to the field of nanophotonics are an attractive alternative to expensive closed-cycle cryostats or LHe-flow cryostats, which could pave the way for the development of high-quality table-top non-classical light sources.
Quantum dot spectroscopy using a single phosphorus donor
NASA Astrophysics Data System (ADS)
Büch, Holger; Fuechsle, Martin; Baker, William; House, Matthew G.; Simmons, Michelle Y.
2015-12-01
Using a deterministic single P donor placed with atomic precision accuracy next to a nanoscale silicon quantum dot, we present a way to analyze the energy spectrum of small quantum dots in silicon by tunnel-coupled transport measurements. The energy-level structure of the quantum dot is observed as resonance features within the transport bias triangles when the donor chemical potential is aligned with states within the quantum dot as confirmed by a numeric rate equation solver SIMON. This technique allows us to independently extract the quantum dot level structure irrespective of the density of states in the leads. Such a method is useful for the investigation of silicon quantum dots in the few-electron regime where the level structure is governed by an intricate interplay between the spin- and the valley-orbit degrees of freedom.
Transient coherent nonlinear spectroscopy of single quantum dots.
Langbein, Wolfgang; Patton, Brian
2007-07-25
We review our recent advances in four-wave mixing spectroscopy of single semiconductor quantum dots using heterodyne spectral interferometry, a novel implementation of transient nonlinear spectroscopy allowing the study of the transient nonlinear polarization emitted from individual electronic transitions in both amplitude and phase. We present experiments on individual excitonic transitions localized in monolayer islands of GaAs/AlAs quantum wells and in self-assembled CdTe/ZnTe quantum dots. We investigate the formation of the photon echo from individual transitions, both with increasing number of transitions in the ensemble, and in the presence of temporal jitter of the energy of a single transition. The detection of amplitude and phase of the signal allows the implementation of a two-dimensional femtosecond spectroscopy, in which mutual coherent coupling of single quantum dot states can observed and quantified. PMID:21483055
Interferometric Quantum-Nondemolition Single-Photon Detectors
NASA Technical Reports Server (NTRS)
Kok, Peter; Lee, Hwang; Dowling, Jonathan
2007-01-01
Two interferometric quantum-nondemolition (QND) devices have been proposed: (1) a polarization-independent device and (2) a polarization-preserving device. The prolarization-independent device works on an input state of up to two photons, whereas the polarization-preserving device works on a superposition of vacuum and single- photon states. The overall function of the device would be to probabilistically generate a unique detector output only when its input electromagnetic mode was populated by a single photon, in which case its output mode would also be populated by a single photon. Like other QND devices, the proposed devices are potentially useful for a variety of applications, including such areas of NASA interest as quantum computing, quantum communication, detection of gravity waves, as well as pedagogical demonstrations of the quantum nature of light. Many protocols in quantum computation and quantum communication require the possibility of detecting a photon without destroying it. The only prior single- photon-detecting QND device is based on quantum electrodynamics in a resonant cavity and, as such, it depends on the photon frequency. Moreover, the prior device can distinguish only between one photon and no photon. The proposed interferometric QND devices would not depend on frequency and could distinguish between (a) one photon and (b) zero or two photons. The first proposed device is depicted schematically in Figure 1. The input electromagnetic mode would be a superposition of a zero-, a one-, and a two-photon quantum state. The overall function of the device would be to probabilistically generate a unique detector output only when its input electromagnetic mode was populated by a single photon, in which case its output mode also would be populated by a single photon.
Quantum dynamics of a single vortex.
Wallraff, A; Lukashenko, A; Lisenfeld, J; Kemp, A; Fistul, M V; Koval, Y; Ustinov, A V
2003-09-11
Vortices occur naturally in a wide range of gases and fluids, from macroscopic to microscopic scales. In Bose-Einstein condensates of dilute atomic gases, superfluid helium and superconductors, the existence of vortices is a consequence of the quantum nature of the system. Quantized vortices of supercurrent are generated by magnetic flux penetrating the material, and play a key role in determining the material properties and the performance of superconductor-based devices. At high temperatures the dynamics of such vortices are essentially classical, while at low temperatures previous experiments have suggested collective quantum dynamics. However, the question of whether vortex tunnelling occurs at low temperatures has been addressed only for large collections of vortices. Here we study the quantum dynamics of an individual vortex in a superconducting Josephson junction. By measuring the statistics of the vortex escape from a controllable pinning potential, we demonstrate the existence of quantized levels of the vortex energy within the trapping potential well and quantum tunnelling of the vortex through the pinning barrier. PMID:12968173
Quantum Overloading Cryptography Using Single-Photon Nonlocality
NASA Astrophysics Data System (ADS)
Tan, Yong-Gang; Cai, Qing-Yu; Shi, Ting-Yun
2007-08-01
Using the single-photon nonlocality, we propose a quantum novel overloading cryptography scheme, in which a single photon carries two bits information in one-way quantum channel. Two commutative modes of the single photon, the polarization mode and the spatial mode, are used to encode secret information. Strict time windows are set to detect the impersonation attack. The spatial mode which denotes the existence of photons is noncommutative with the phase of the photon, so that our scheme is secure against photon-number-splitting attack. Our protocol may be secure against individual attack.
Signatures of single quantum dots in graphene nanoribbons within the quantum Hall regime
NASA Astrophysics Data System (ADS)
Tóvári, Endre; Makk, Péter; Rickhaus, Peter; Schönenberger, Christian; Csonka, Szabolcs
2016-06-01
We report on the observation of periodic conductance oscillations near quantum Hall plateaus in suspended graphene nanoribbons. They are attributed to single quantum dots that are formed in the narrowest part of the ribbon, in the valleys and hills of a disorder potential. In a wide flake with two gates, a double-dot system's signature has been observed. Electrostatic confinement is enabled in single-layer graphene due to the gaps that are formed between the Landau levels, suggesting a way to create gate-defined quantum dots that can be accessed with quantum Hall edge states.We report on the observation of periodic conductance oscillations near quantum Hall plateaus in suspended graphene nanoribbons. They are attributed to single quantum dots that are formed in the narrowest part of the ribbon, in the valleys and hills of a disorder potential. In a wide flake with two gates, a double-dot system's signature has been observed. Electrostatic confinement is enabled in single-layer graphene due to the gaps that are formed between the Landau levels, suggesting a way to create gate-defined quantum dots that can be accessed with quantum Hall edge states. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR00187D
Authenticated multi-user quantum key distribution with single particles
NASA Astrophysics Data System (ADS)
Lin, Song; Wang, Hui; Guo, Gong-De; Ye, Guo-Hua; Du, Hong-Zhen; Liu, Xiao-Fen
2016-03-01
Quantum key distribution (QKD) has been growing rapidly in recent years and becomes one of the hottest issues in quantum information science. During the implementation of QKD on a network, identity authentication has been one main problem. In this paper, an efficient authenticated multi-user quantum key distribution (MQKD) protocol with single particles is proposed. In this protocol, any two users on a quantum network can perform mutual authentication and share a secure session key with the assistance of a semi-honest center. Meanwhile, the particles, which are used as quantum information carriers, are not required to be stored, therefore the proposed protocol is feasible with current technology. Finally, security analysis shows that this protocol is secure in theory.
Process tomography via sequential measurements on a single quantum system
NASA Astrophysics Data System (ADS)
Bassa, Humairah; Goyal, Sandeep K.; Choudhary, Sujit K.; Uys, Hermann; Diósi, Lajos; Konrad, Thomas
2015-09-01
We utilize a discrete (sequential) measurement protocol to investigate quantum process tomography of a single two-level quantum system, with an unknown initial state, undergoing Rabi oscillations. The ignorance of the dynamical parameters is encoded into a continuous-variable classical system which is coupled to the two-level quantum system via a generalized Hamiltonian. This combined estimate of the quantum state and dynamical parameters is updated by using the information obtained from sequential measurements on the quantum system and, after a sufficient waiting period, faithful state monitoring and parameter determination is obtained. Numerical evidence is used to demonstrate the convergence of the state estimate to the true state of the hybrid system.
Operating quantum waveguide circuits with superconducting single-photon detectors
NASA Astrophysics Data System (ADS)
Natarajan, C. M.; Peruzzo, A.; Miki, S.; Sasaki, M.; Wang, Z.; Baek, B.; Nam, S.; Hadfield, R. H.; O'Brien, J. L.
2010-05-01
Advanced quantum information science and technology (QIST) applications place exacting demands on optical components. Quantum waveguide circuits offer a route to scalable QIST on a chip. Superconducting single-photon detectors (SSPDs) provide infrared single-photon sensitivity combined with low dark counts and picosecond timing resolution. In this study, we bring these two technologies together. Using SSPDs we observe a two-photon interference visibility of 92.3±1.0% in a silica-on-silicon waveguide directional coupler at λ =804 nm—higher than that measured with silicon detectors (89.9±0.3%). We further operated controlled-NOT gate and quantum metrology circuits with SSPDs. These demonstrations present a clear path to telecom-wavelength quantum waveguide circuits.
Strong Single-Photon Coupling in Superconducting Quantum Magnetomechanics
NASA Astrophysics Data System (ADS)
Via, Guillem; Kirchmair, Gerhard; Romero-Isart, Oriol
2015-04-01
We show that the inductive coupling between the quantum mechanical motion of a superconducting microcantilever and a flux-dependent microwave quantum circuit can attain the strong single-photon nanomechanical coupling regime with feasible experimental parameters. We propose to use a superconducting strip, which is in the Meissner state, at the tip of a cantilever. A pickup coil collects the flux generated by the sheet currents induced by an external quadrupole magnetic field centered at the strip location. The position-dependent magnetic response of the superconducting strip, enhanced by both diamagnetism and demagnetizing effects, leads to a strong magnetomechanical coupling to quantum circuits.
Generalized Limits for Single-Parameter Quantum Estimation
Boixo, Sergio; Flammia, Steven T.; Caves, Carlton M.; Geremia, JM
2007-03-02
We develop generalized bounds for quantum single-parameter estimation problems for which the coupling to the parameter is described by intrinsic multisystem interactions. For a Hamiltonian with k-system parameter-sensitive terms, the quantum limit scales as 1/N{sup k}, where N is the number of systems. These quantum limits remain valid when the Hamiltonian is augmented by any parameter-independent interaction among the systems and when adaptive measurements via parameter-independent coupling to ancillas are allowed.
Quantum Computation and Quantum Metrology based on Single Electron Spin in Diamond
NASA Astrophysics Data System (ADS)
Du, Jiangfeng
2015-03-01
It is of great challenge to perform the accurate controlling the electron spin qubits in realistic system, due to the noises aroused from the noisy spin bath and the driving field. Firstly, we adopted dynamically corrected gates to realize robust and high-fidelity quantum gates. In this work, the quantum gate's performance was pushed to T1r limit. Then, a new Rabi Oscillations (ROs) resulting from Landau-Zener (LZ) transitions is observed useful to suppress the fluctuations of the driving field. Besides, quantum error correction is experimentally employed to overcome the noise effect in diamonds. Precise quantum control and effectively supressing noise of the environment are of great importance for quantum metrology. We succeeded in sensing and atomic-scale analysis of single nuclear spin clusters in diamond at room temperature, and also have succeed to detect a few nuclear spins with single spin sensitivity.
Quantum Yield of Single Surface Plasmons Generated by a Quantum Dot Coupled with a Silver Nanowire.
Li, Qiang; Wei, Hong; Xu, Hongxing
2015-12-01
The interactions between surface plasmons (SPs) in metal nanostructures and excitons in quantum emitters (QEs) lead to many interesting phenomena and potential applications that are strongly dependent on the quantum yield of SPs. The difficulty in distinguishing all the possible exciton recombination channels hinders the experimental determination of SP quantum yield. Here, we experimentally measured for the first time the quantum yield of single SPs generated by the exciton-plasmon coupling in a system composed of a single quantum dot and a silver nanowire (NW). By utilizing the SP guiding property of the NW, the decay rates of all the exciton recombination channels, i.e., direct free space radiation channel, SP generation channel, and nonradiative damping channel, are quantitatively obtained. It is determined that the optimum emitter-NW coupling distance for the largest SP quantum yield is about 10 nm, resulting from the different distance-dependent decay rates of the three channels. These results are important for manipulating the coupling between plasmonic nanostructures and QEs and developing on-chip quantum plasmonic devices for potential nanophotonic and quantum information applications. PMID:26583200
Superconducting Quantum Interference Single-Electron Transistor
NASA Astrophysics Data System (ADS)
Enrico, Emanuele; Giazotto, Francesco
2016-06-01
We propose the concept of a quantized single-electron source based on the interplay between Coulomb blockade and magnetic flux-controllable superconducting proximity effect. We show that flux dependence of the induced energy gap in the density of states of a nanosized metallic wire can be exploited as an efficient tunable energy barrier which enables charge-pumping configurations with enhanced functionalities. This control parameter strongly affects the charging landscape of a normal metal island with non-negligible Coulombic energy. Under a suitable evolution of a time-dependent magnetic flux the structure behaves like a turnstile for single electrons in a fully electrostatic regime.
Single-Atom Gating of Quantum State Superpositions
Moon, Christopher
2010-04-28
The ultimate miniaturization of electronic devices will likely require local and coherent control of single electronic wavefunctions. Wavefunctions exist within both physical real space and an abstract state space with a simple geometric interpretation: this state space - or Hilbert space - is spanned by mutually orthogonal state vectors corresponding to the quantized degrees of freedom of the real-space system. Measurement of superpositions is akin to accessing the direction of a vector in Hilbert space, determining an angle of rotation equivalent to quantum phase. Here we show that an individual atom inside a designed quantum corral1 can control this angle, producing arbitrary coherent superpositions of spatial quantum states. Using scanning tunnelling microscopy and nanostructures assembled atom-by-atom we demonstrate how single spins and quantum mirages can be harnessed to image the superposition of two electronic states. We also present a straightforward method to determine the atom path enacting phase rotations between any desired state vectors. A single atom thus becomes a real-space handle for an abstract Hilbert space, providing a simple technique for coherent quantum state manipulation at the spatial limit of condensed matter.
Single electron tunneling in double and triple quantum wells
NASA Astrophysics Data System (ADS)
Filikhin, I.; Karoui, A.; Vlahovic, B.
2016-03-01
Electron localization and tunneling in laterally distributed double quantum well (DQW) and triple quantum well (TQW) are studied. Triangular configuration for the TQWs as well as various quantum well (QW) shapes and asymmetry are considered. The effect of adding a third well to a DQW is investigated as a weakly coupled system. InAs/GaAs DQWs and TQWs were modeled using single subband effective mass approach with effective potential simulating the strain effect. Electron localization dynamics in DQW and TQW over the whole spectrum is studied by varying the inter-dot distances. The electron tunneling appeared highly sensitive to small violations of the DQW mirror symmetry. We show that the presence of a third dot increases the tunneling in the DQW. The dependence of the tunneling in quantum dot (QD) arrays on inter-dot distances is also discussed.
Quantum Interference Induced Photon Blockade in a Coupled Single Quantum Dot-Cavity System
Tang, Jing; Geng, Weidong; Xu, Xiulai
2015-01-01
We propose an experimental scheme to implement a strong photon blockade with a single quantum dot coupled to a nanocavity. The photon blockade effect can be tremendously enhanced by driving the cavity and the quantum dot simultaneously with two classical laser fields. This enhancement of photon blockade is ascribed to the quantum interference effect to avoid two-photon excitation of the cavity field. Comparing with Jaynes-Cummings model, the second-order correlation function at zero time delay g(2)(0) in our scheme can be reduced by two orders of magnitude and the system sustains a large intracavity photon number. A red (blue) cavity-light detuning asymmetry for photon quantum statistics with bunching or antibunching characteristics is also observed. The photon blockade effect has a controllable flexibility by tuning the relative phase between the two pumping laser fields and the Rabi coupling strength between the quantum dot and the pumping field. Moreover, the photon blockade scheme based on quantum interference mechanism does not require a strong coupling strength between the cavity and the quantum dot, even with the pure dephasing of the system. This simple proposal provides an effective way for potential applications in solid state quantum computation and quantum information processing. PMID:25783560
Efficient single-photon entanglement concentration for quantum communications
NASA Astrophysics Data System (ADS)
Zhou, Lan; Sheng, Yu-Bo
2014-02-01
We present two entanglement concentration protocols for single-photon entanglement. The first protocol is implemented with linear optics. With the help of the 50:50 beam splitter, variable beam splitter and an auxiliary photon, a less-entangled single-photon state can be concentrated into a maximally single-photon entangled state with some probability. The second protocol is implemented with the cross-Kerr nonlinearity. With the help of the cross-Kerr nonlinearity, the sophisticated single photon detector is not required. Moreover, the second protocol can be reused to get higher success probability. All these advantages may make the protocols useful in the long-distance quantum communication.
Pilot-Wave Quantum Theory with a Single Bohm's Trajectory
NASA Astrophysics Data System (ADS)
Avanzini, Francesco; Fresch, Barbara; Moro, Giorgio J.
2016-05-01
The representation of a quantum system as the spatial configuration of its constituents evolving in time as a trajectory under the action of the wave-function, is the main objective of the de Broglie-Bohm theory (or pilot wave theory). However, its standard formulation is referred to the statistical ensemble of its possible trajectories. The statistical ensemble is introduced in order to establish the exact correspondence (the Born's rule) between the probability density on the spatial configurations and the quantum distribution, that is the squared modulus of the wave-function. In this work we explore the possibility of using the pilot wave theory at the level of a single Bohm's trajectory, that is a single realization of the time dependent configuration which should be representative of a single realization of the quantum system. The pilot wave theory allows a formally self-consistent representation of quantum systems as a single Bohm's trajectory, but in this case there is no room for the Born's rule at least in its standard form. We will show that a correspondence exists between the statistical distribution of configurations along the single Bohm's trajectory and the quantum distribution for a subsystem interacting with the environment in a multicomponent system. To this aim, we present the numerical results of the single Bohm's trajectory description of the model system of six confined planar rotors with random interactions. We find a rather close correspondence between the coordinate distribution of one rotor, the others representing the environment, along its trajectory and the time averaged marginal quantum distribution for the same rotor. This might be considered as the counterpart of the standard Born's rule when the pilot wave theory is applied at the level of single Bohm's trajectory. Furthermore a strongly fluctuating behavior with a fast loss of correlation is found for the evolution of each rotor coordinate. This suggests that a Markov process might
Quantum private query based on single-photon interference
NASA Astrophysics Data System (ADS)
Xu, Sheng-Wei; Sun, Ying; Lin, Song
2016-08-01
Quantum private query (QPQ) has become a research hotspot recently. Specially, the quantum key distribution (QKD)-based QPQ attracts lots of attention because of its practicality. Various such kind of QPQ protocols have been proposed based on different technologies of quantum communications. Single-photon interference is one of such technologies, on which the famous QKD protocol GV95 is just based. In this paper, we propose two QPQ protocols based on single-photon interference. The first one is simpler and easier to realize, and the second one is loss tolerant and flexible, and more practical than the first one. Furthermore, we analyze both the user privacy and the database privacy in the proposed protocols.
Authenticated Quantum Key Distribution with Collective Detection using Single Photons
NASA Astrophysics Data System (ADS)
Huang, Wei; Xu, Bing-Jie; Duan, Ji-Tong; Liu, Bin; Su, Qi; He, Yuan-Hang; Jia, Heng-Yue
2016-05-01
We present two authenticated quantum key distribution (AQKD) protocols by utilizing the idea of collective (eavesdropping) detection. One is a two-party AQKD protocol, the other is a multiparty AQKD protocol with star network topology. In these protocols, the classical channels need not be assumed to be authenticated and the single photons are used as the quantum information carriers. To achieve mutual identity authentication and establish a random key in each of the proposed protocols, only one participant should be capable of preparing and measuring single photons, and the main quantum ability that the rest of the participants should have is just performing certain unitary operations. Security analysis shows that these protocols are free from various kinds of attacks, especially the impersonation attack and the man-in-the-middle (MITM) attack.
Quantum private query based on single-photon interference
NASA Astrophysics Data System (ADS)
Xu, Sheng-Wei; Sun, Ying; Lin, Song
2016-05-01
Quantum private query (QPQ) has become a research hotspot recently. Specially, the quantum key distribution (QKD)-based QPQ attracts lots of attention because of its practicality. Various such kind of QPQ protocols have been proposed based on different technologies of quantum communications. Single-photon interference is one of such technologies, on which the famous QKD protocol GV95 is just based. In this paper, we propose two QPQ protocols based on single-photon interference. The first one is simpler and easier to realize, and the second one is loss tolerant and flexible, and more practical than the first one. Furthermore, we analyze both the user privacy and the database privacy in the proposed protocols.
Simulating quantum Brownian motion with single trapped ions
Maniscalco, S.; Piilo, J.; Intravaia, F.; Petruccione, F.; Messina, A.
2004-05-01
We study the open system dynamics of a harmonic oscillator coupled with an artificially engineered reservoir. We single out the reservoir and system variables governing the passage between Lindblad-type and non-Lindblad-type dynamics of the reduced system's oscillator. We demonstrate the existence of conditions under which virtual exchanges of energy between system and reservoir take place. We propose to use a single trapped ion coupled to engineered reservoirs in order to simulate quantum Brownian motion.
Stamping single wall nanotubes for circuit quantum electrodynamics
Viennot, J. J. Kontos, T.; Palomo, J.
2014-03-17
We report on a dry transfer technique for single wall carbon nanotube devices, which allows to embed them in high finesse microwave cavity. We demonstrate the ground state charge readout and a quality factor of about 3000 down to the single photon regime. This technique allows to make devices such as double quantum dots, which could be instrumental for achieving the strong spin photon coupling. It can easily be extended to generic carbon nanotube based microwave devices.
Single particle density of trapped interacting quantum gases
Bala, Renu; Bosse, J.; Pathak, K. N.
2015-05-15
An expression for single particle density for trapped interacting gases has been obtained in first order of interaction using Green’s function method. Results are easily simplified for homogeneous quantum gases and are found to agree with famous results obtained by Huang-Yang-Luttinger and Lee-Yang.
Experimental realization of a strongly interacting quantum memory
NASA Astrophysics Data System (ADS)
Li, Lin; Kuzmich, Alex
2016-05-01
A quantum memory is a device which enables the storage and retrieval of quantum states of light. Ground atomic states interact only weakly with the environment and with each other, enabling memories with long storage times. However, for scalable generation and distillation of entanglement within distributed quantum information systems, it is desirable to controllably switch on and off interactions between the individual atoms. We realize a strongly interacting quantum memory by coupling the ground state of an ultra-cold atomic gas to a highly excited Rydberg state. The memory is subsequently retrieved into a propagating light field which is measured using the Hanbury Brown-Twiss photo-electric detection. The results reveal memory transformation from an initially prepared coherent state into the state of single excitation.
Complete quantum control of a single quantum dot spin using ultrafast optical pulses.
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
Quantum Information Science with Single Atoms and Photons
NASA Astrophysics Data System (ADS)
Kimble, H. J.
2003-03-01
Cavity quantum electrodynamics (QED) offers powerful possibilities for the deterministic control of atom-photon interactions quantum by quantum [1]. Indeed, modern experiments in cavity QED have achieved the exceptional circumstance of strong coupling, for which single quanta can profoundly impact the dynamics of the atom-cavity system. The diverse accomplishments of this field set the stage for advances into yet broader frontiers in quantum information science for which cavity QED offers unique advantages, including the creation of quantum networks [2]. The primary technical challenge on the road toward such scientific goals is the need to trap and localize atoms within a cavity in a setting suitable for strong coupling. Two separate experiments in our group have achieved significant milestones in this quest, namely the real-time trapping and tracking of single atoms in cavity QED [3-5]. In one experiment, an atom is trapped by an auxiliary field that functions as a far-detuned dipole-force trap (FORT) [3,4], with trap lifetime 3s, which should be compared to the nanosecond time scale for internal dynamics of the atom-cavity system. In a second experiment, we rely upon light forces at the single-photon level to trap a single atom within the cavity mode [5]. As illustrated by the movies available at http://www.its.caltech.edu/ qoptics/atomorbits/, these reconstructions reveal single atoms bound in orbit by the mechanical forces associated with single photons, and realize a new form of microscopy. Over the duration of the observation, the sensitivity is near the standard quantum limit for sensing the motion of a Cesium atom. This work is supported by the NSF, by the Caltech MURI for Quantum Networks administered by the ARO, and by the ONR. 1. For a review, see contributions in the Special Issue of Physica Scripta T76 (1998). 2. J. I. Cirac, S. J. van Enk, P. Zoller, H. J. Kimble, and H. Mabuchi, Physica Scripta T76, 223 (1998). 3. J. Ye, D. W. Vernooy, and H. J
A versatile source of single photons for quantum information processing
NASA Astrophysics Data System (ADS)
Förtsch, Michael; Fürst, Josef U.; Wittmann, Christoffer; Strekalov, Dmitry; Aiello, Andrea; Chekhova, Maria V.; Silberhorn, Christine; Leuchs, Gerd; Marquardt, Christoph
2013-05-01
The generation of high-quality single-photon states with controllable narrow spectral bandwidths and central frequencies is key to facilitate efficient coupling of any atomic system to non-classical light fields. Such an interaction is essential in numerous experiments for fundamental science and applications in quantum communication and information processing, as well as in quantum metrology. Here we implement a fully tunable, narrow-band and efficient single-photon source based on a whispering gallery mode resonator. Our disk-shaped, monolithic and intrinsically stable resonator is made of lithium niobate and supports a cavity-assisted spontaneous parametric down-conversion process. The generated photon pairs are emitted into two highly tunable resonator modes. We verify wavelength tuning over 100 nm of both modes with controllable bandwidth between 7.2 and 13 MHz. Heralding of single photons yields anti-bunching with g(2)(0)<0.2.
A quantum interface between single atoms and nanophotonic structures
NASA Astrophysics Data System (ADS)
Thompson, Jeffrey Douglas
Strong interactions between light and atoms at the single-quantum level are an important ingredient for quantum technologies, as well as for studies of fundamental effects in quantum optics. This thesis describes the development of a novel experimental platform that allows for trapping a single rubidium atom in the evanescent mode of a nano-fabricated optical cavity with sub-wavelength dimensions. By virtue of their small size, these cavities provide extremely large atom-photon coupling strengths and good prospects for scalability and integration into complex quantum optical circuits. Positioning the atom near the nano-structure is accomplished using a scanning optical tweezer dipole trap. As a first application, we have demonstrated a coherent optical switch, where a single gate photon controls the propagation of many subsequent signal photons, with the interaction mediated by the atom and cavity. We have also shown that the optical response of the combined atom-cavity system is nonlinear at the level of one or two photons.
Complete single-horizon quantum corrected black hole spacetime
Peltola, Ari; Kunstatter, Gabor
2009-03-15
We show that a semiclassical polymerization of the interior of Schwarzschild black holes gives rise to a tantalizing candidate for a nonsingular, single-horizon black hole spacetime. The exterior has nonzero quantum stress energy but closely approximates the classical spacetime for macroscopic black holes. The interior exhibits a bounce at a microscopic scale and then expands indefinitely to a Kantowski-Sachs spacetime. Polymerization therefore removes the singularity and produces a scenario reminiscent of past proposals for universe creation via quantum effects inside a black hole.
Single to quadruple quantum dots with tunable tunnel couplings
Takakura, T.; Noiri, A.; Obata, T.; Yoneda, J.; Yoshida, K.; Otsuka, T.; Tarucha, S.
2014-03-17
We prepare a gate-defined quadruple quantum dot to study the gate-tunability of single to quadruple quantum dots with finite inter-dot tunnel couplings. The measured charging energies of various double dots suggest that the dot size is governed by the gate geometry. For the triple and quadruple dots, we study the gate-tunable inter-dot tunnel couplings. For the triple dot, we find that the effective tunnel coupling between side dots significantly depends on the alignment of the center dot potential. These results imply that the present quadruple dot has a gate performance relevant for implementing spin-based four-qubits with controllable exchange couplings.
Quantum Otto engine using a single ion and a single thermal bath
NASA Astrophysics Data System (ADS)
Biswas, Asoka; Chand, Suman
2016-05-01
Quantum heat engines employ a quantum system as the working fluid, that gives rise to large work efficiency, beyond the limit for classical heat engines. Existing proposals for implementing quantum heat engines require that the system interacts with the hot bath and the cold bath (both modelled as a classical system) in an alternative fashion and therefore assumes ability to switch off the interaction with the bath during a certain stage of the heat-cycle. However, it is not possible to decouple a quantum system from its always-on interaction with the bath without use of complex pulse sequences. It is also hard to identify two different baths at two different temperatures in quantum domain, that sequentially interact with the system. Here, we show how to implement a quantum Otto engine without requiring to decouple the bath in a sequential manner. This is done by considering a single thermal bath, coupled to a single trapped ion. The electronic degree of freedom of the ion is chosen as a two-level working fluid while the vibrational degree of freedom plays the role of the cold bath. Measuring the electronic state mimics the release of heat into the cold bath. Thus, our model is fully quantum and exhibits very large work efficiency, asymptotically close to unity.
NASA Astrophysics Data System (ADS)
Vuckovic, Jelena
2009-05-01
Quantum dots in photonic crystals are interesting both as a testbed for fundamental cavity quantum electrodynamics (QED) experiments, as well as a platform for quantum and classical information processing. Quantum dot-photonic crystal cavity QED has been probed both in photoluminescence and coherently, by resonant light scattering from such a system [1]. In the latter case, both intensity and photon statistics of the reflected beam have been analyzed as a function of wavelength, leading to observation of effects such as photon blockade and photon induced tunneling - for the first time in solid state [2]. The system has also been employed to achieve a controlled phase and amplitude modulation between two modes of light at the single photon level [3] - nonlinearity observed so far only in atomic physics systems. These demonstrations lie at the core of a number of proposals for quantum information processing, and could also be employed to build novel devices, such as optical switches controlled at a single photon level. [4pt] [1] Dirk Englund, Andrei Faraon, Ilya Fushman, Nick Stoltz, Pierre Petroff, and Jelena Vuckovic, ``Controlling cavity reflectivity with a single quantum dot," Nature ,ol. 450, No. 7171, pp. 857-861, December 2007[0pt] [2] Andrei Faraon, Ilya Fushman, Dirk Englund, Nick Stoltz, Pierre Petroff, and Jelena Vuckovic, ``Coherent generation of nonclassical light on a chip via photon-induced tunneling and blockade," Nature Physics ,ol. 4, pp. 859 - 863 (2008)[0pt] [3] Ilya Fushman, Dirk Englund, Andrei Faraon, Nick Stoltz, Pierre Petroff, and Jelena Vuckovic, ``Controlled phase shift with a single quantum dot," Science ,ol. 320, number 5877, pp. 769-772 ( 2008)
Secret sharing with a single d -level quantum system
NASA Astrophysics Data System (ADS)
Tavakoli, Armin; Herbauts, Isabelle; Żukowski, Marek; Bourennane, Mohamed
2015-09-01
We give an example of a wide class of problems for which quantum-information protocols based on multisystem entanglement can be mapped into much simpler ones involving one system. Secret sharing is a cryptographic primitive which plays a central role in various secure multiparty computation tasks and management of keys in cryptography. In secret sharing protocols, a classical message is divided into shares given to recipient parties in such a way that some number of parties need to collaborate in order to reconstruct the message. Quantum protocols for the task commonly rely on multipartite GHZ entanglement. We present a multiparty secret sharing protocol which requires only sequential communication of a single quantum d -level system (for any prime d ). It has huge advantages in scalability and can be realized with state-of-the-art technology.
Quantum benchmarks for pure single-mode Gaussian states.
Chiribella, Giulio; Adesso, Gerardo
2014-01-10
Teleportation and storage of continuous variable states of light and atoms are essential building blocks for the realization of large-scale quantum networks. Rigorous validation of these implementations require identifying, and surpassing, benchmarks set by the most effective strategies attainable without the use of quantum resources. Such benchmarks have been established for special families of input states, like coherent states and particular subclasses of squeezed states. Here we solve the longstanding problem of defining quantum benchmarks for general pure Gaussian single-mode states with arbitrary phase, displacement, and squeezing, randomly sampled according to a realistic prior distribution. As a special case, we show that the fidelity benchmark for teleporting squeezed states with totally random phase and squeezing degree is 1/2, equal to the corresponding one for coherent states. We discuss the use of entangled resources to beat the benchmarks in experiments. PMID:24483875
Vacuum Rabi spectra of a single quantum emitter.
Ota, Yasutomo; Ohta, Ryuichi; Kumagai, Naoto; Iwamoto, Satoshi; Arakawa, Yasuhiko
2015-04-10
We report the observation of the vacuum Rabi splitting of a single quantum emitter by measuring its direct spontaneous emission into free space. We use a semiconductor quantum dot inside a photonic crystal nanocavity, in conjunction with an appropriate cavity design and filtering with a polarizer and an aperture, enabling the extraction of the inherently weak emitter's signal. The emitter's vacuum Rabi spectra exhibit clear differences from those measured by detecting the cavity photon leakage. Moreover, we observe an asymmetric vacuum Rabi spectrum induced by interference between the emitter and cavity detection channels. Our observations lay the groundwork for accessing various cavity quantum electrodynamics phenomena that manifest themselves only in the emitter's direct spontaneous emission. PMID:25910123
Single bump, two-color quantum dot camera
NASA Astrophysics Data System (ADS)
Varley, E.; Lenz, M.; Lee, S. J.; Brown, J. S.; Ramirez, D. A.; Stintz, A.; Krishna, S.; Reisinger, Axel; Sundaram, Mani
2007-08-01
The authors report a two-color, colocated quantum dot based imaging system used to take multicolor images using a single focal plane array (FPA). The dots-in-a-well (DWELL) detectors consist of an active region composed of InAs quantum dots embedded in In.15Ga.85As quantum wells. DWELL samples were grown using molecular beam epitaxy and fabricated into 320×256 focal plane arrays with indium bumps. The FPA was then hybridized to an Indigo ISC9705 readout circuit and tested. Calibrated blackbody measurements at a device temperature of 77K yield midwave infrared and long wave infrared noise equivalent difference in temperature of ˜55 and 70mK.
Manipulating single electron spins and coherence in quantum dots
NASA Astrophysics Data System (ADS)
Awschalom, David
2008-05-01
The non-destructive detection of a single electron spin in a quantum dot (QD) is demonstrated using a time- averaged magneto-optical Kerr rotation measurementootnotetextJ. Berezovsky, M. H. Mikkelsen, O. Gywat, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, Science 314, 1916 (2006).. This technique provides a means to directly probe the spin off- resonance, thus minimally disturbing the system. Furthermore, the ability to sequentially initialize, manipulate, and read out the state of a qubit, such as an electron spin in a quantum dot, is necessary for virtually any scheme for quantum information processing. In addition to the time-averaged measurements, we have extended the single dot KR technique into the time domain with pulsed pump and probe lasers, allowing the observation of the coherent evolution of an electron spin stateootnotetextM. H. Mikkelsen, J. Berezovsky, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, Nature Physics 3, 770 (2007).. The dot is formed by interface fluctuations of a GaAs quantum well and embedded in a diode structure to allow controllable gating/charging of the QD. To enhance the small single spin signal, the QD is positioned within a vertical optical cavity. Observations of coherent single spin precession in an applied magnetic field allow a direct measurement of the electron g-factor and transverse spin lifetime. These measurements reveal information about the relevant spin decoherence mechanisms, while also providing a sensitive probe of the local nuclear spin environment. Finally, we have recently eveloped a scheme for high speed all-optical manipulation of the spin state that enables multiple operations within the coherence timeootnotetextJ. Berezovsky, M. H. Mikkelsen, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, accepted for publication (2008).. The results represent progress toward the control and coupling of single spins and photons for quantum information processingootnotetextS. Ghosh, W.H. Wang, F. M. Mendoza, R. C
Realizing quantum advantage without entanglement in single-photon states
NASA Astrophysics Data System (ADS)
Maldonado Trapp, Alejandra; Solano, Pablo; Hu, Anzi; Clark, Charles W.
2016-05-01
Quantum discord expresses quantum correlations beyond those associated with entanglement. Although it has been extensively studied theoretically, quantum discord has yet to become a standard tool in experimental studies of correlation. We propose a class of experiments in which quantum correlations are present in the absence of entanglement, and are best understood in terms of quantum discord.. These utilize X-states of two qubits, which correspond to the polarization and the optical path of a single photon within a Mach-Zehnder interferometer. We show how to produce states with diverse measures of discord and entanglement, including the case of discord without entanglement. With these states we show how a classical random variable K can be encoded by Alice and decoded by Bob. Using our previous results we analytically study the correlations between the spin and path qubits and its relation with the information about K that can be decoded by Bob using local measurements with or without two-qubit gate operations.
Single Motional Quantum Exchange between Independently Trapped Ions
NASA Astrophysics Data System (ADS)
Brown, K. R.; Ospelkaus, C.; Colombe, Y.; Wilson, A. C.; Leibfried, D.; Wineland, D. J.
2011-05-01
The Coulomb coupling of ions in separate potential wells is a key feature of proposals to implement quantum simulation and could enable logic operations to be performed in a multi-zone quantum information processor without the requirement of bringing the ion qubits into the same trapping potential. It might also extend the capabilities of quantum logic spectroscopy to ions that cannot be trapped in the same potential well as the measurement ion, such as oppositely charged ions or even antimatter particles. We report recent results demonstrating tunable coupling of two 9Be+ ions held in trapping potentials separated by 40 μm. The ions are trapped 40 μm above the surface of a microfabricated planar trap with independently tunable axial frequencies of ~4 MHz. The trap is cooled to 4.2 K with a helium bath cryostat to suppress anomalous heating and to extend the lifetime of ions from minutes to days. By preparing approximate motional number states with n=0 and n=1 in the respective wells, and tuning the confining wells into resonance, a single quantum of motion is exchanged between the ions in ~200 μs. Work supported by IARPA, DARPA, ONR, and the NIST Quantum Information Program.
Single and Multi-Channel Carbon-based Quantum Dragons
NASA Astrophysics Data System (ADS)
Inkoom, Godfred; Abdurazakov, Omadillo; Novotny, Mark
2015-03-01
In the coherent regime for electrical conductance measurements, two semi-infinite leads are connected to a finite nanostructure, and the nano-device conductance is calculated using the Landauer formula. Any channel k that has transmission for electrons with energy E, \\calTk (E) =1 contributes the conductance quantum G0 = 2e2 / h . Any nano-device with at least one \\calTk (E) =1 is called a quantum dragon. The transmission probability \\calTk (E) can be obtained from the solution of the time-independent Schrödinger equation. Uniform leads connected to armchair single-walled carbon nanotubes (SWCNTs) have calT (E) =1, while when connected to zigzag SWCNT the calT (E) is less than unity. Appropriately dimerized leads connected to zigzag SWCNTs are quantum dragons, while when connected to armchair SWCNTs calT (E) is less than unity. We have generalized the matrix method and mapping methods of in order to investigate SWCNTs that can be multi-channel quantum dragons. For example, one can use armchair SWCNT leads to connect to an armchair SWCNT to try to produce a multi-channel quantum dragon. Supported in part by NSF Grant DMR-1206233.
Single quantum dot controls a plasmonic cavity's scattering and anisotropy.
Hartsfield, Thomas; Chang, Wei-Shun; Yang, Seung-Cheol; Ma, Tzuhsuan; Shi, Jinwei; Sun, Liuyang; Shvets, Gennady; Link, Stephan; Li, Xiaoqin
2015-10-01
Plasmonic cavities represent a promising platform for controlling light-matter interaction due to their exceptionally small mode volume and high density of photonic states. Using plasmonic cavities for enhancing light's coupling to individual two-level systems, such as single semiconductor quantum dots (QD), is particularly desirable for exploring cavity quantum electrodynamic (QED) effects and using them in quantum information applications. The lack of experimental progress in this area is in part due to the difficulty of precisely placing a QD within nanometers of the plasmonic cavity. Here, we study the simplest plasmonic cavity in the form of a spherical metallic nanoparticle (MNP). By controllably positioning a semiconductor QD in the close proximity of the MNP cavity via atomic force microscope (AFM) manipulation, the scattering spectrum of the MNP is dramatically modified due to Fano interference between the classical plasmonic resonance of the MNP and the quantized exciton resonance in the QD. Moreover, our experiment demonstrates that a single two-level system can render a spherical MNP strongly anisotropic. These findings represent an important step toward realizing quantum plasmonic devices. PMID:26372957
In situ tuning the single photon emission from single quantum dots through hydrostatic pressure
Wu, Xuefei; Dou, Xiuming; Ding, Kun; Zhou, Pengyu; Ni, Haiqiao; Niu, Zhichuan; Jiang, Desheng; Sun, Baoquan
2013-12-16
We demonstrate that exciton emission wavelength in InAs/GaAs quantum dots (QDs) can be shifted up to 160 nm using hydrostatic pressure (0.4–4 GPa) in situ in an optical cryostat through an improved diamond anvil cell driven by piezoelectric actuator. It is confirmed that the high pressure does not destroy the photon anti-bunching properties of single QD emitter. Exciton emission intensity is not obviously weakened under the pressure range of 0–4 GPa. Such a tunable QD single photon emitter enables a flexibly tuned source for quantum optical experiments.
Single-shot optical readout of a quantum bit using cavity quantum electrodynamics
NASA Astrophysics Data System (ADS)
Sun, Shuo; Waks, Edo
2016-07-01
We propose a method to perform single-shot optical readout of a quantum bit (qubit) using cavity quantum electrodynamics. We selectively couple the optical transitions associated with different qubit basis states to the cavity and utilize the change in cavity transmissivity to generate a qubit readout signal composed of many photons. We show that this approach enables single-shot optical readout even when the qubit does not have a good cycling transition, which is required for standard resonance fluorescence measurements. We calculate the probability that the measurement detects the correct qubit state using the example of a quantum-dot spin under various experimental conditions and demonstrate that it can exceed 0.99.
Bidirectional imperfect quantum teleportation with a single Bell state
NASA Astrophysics Data System (ADS)
Kiktenko, E. O.; Popov, A. A.; Fedorov, A. K.
2016-06-01
We present a bidirectional modification of the standard one-qubit teleportation protocol, where both Alice and Bob transfer noisy versions of their qubit states to each other by using single Bell state and auxiliary (trigger) qubits. Three schemes are considered: the first where the actions of parties are governed by two independent quantum random triggers, the second with single random trigger, and the third as a mixture of the first two. We calculate the fidelities of teleportation for all schemes and find a condition on correlation between trigger qubits in the mixed scheme which allows us to overcome the classical fidelity boundary of 2/3. We apply the Choi-Jamiolkowski isomorphism to the quantum channels obtained in order to investigate an interplay between their ability to transfer the information, entanglement-breaking property, and auxiliary classical communication needed to form correlations between trigger qubits. The suggested scheme for bidirectional teleportation can be realized by using current experimental tools.
Single-copy entanglement in critical quantum spin chains
NASA Astrophysics Data System (ADS)
Eisert, J.; Cramer, M.
2005-10-01
We consider the single-copy entanglement as a quantity to assess quantum correlations in the ground state in quantum many-body systems. We show for a large class of models that already on the level of single specimens of spin chains, criticality is accompanied with the possibility of distilling a maximally entangled state of arbitrary dimension from a sufficiently large block deterministically, with local operations and classical communication. These analytical results—which refine previous results on the divergence of block entropy as the rate at which maximally entangled pairs can be distilled from many identically prepared chains—are made quantitative for general isotropic translationally invariant spin chains that can be mapped onto a quasifree fermionic system, and for the anisotropic XY model. For the XX model, we provide the asymptotic scaling of ˜(1/6)log2(L) , and contrast it with the block entropy.
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.
NASA Astrophysics Data System (ADS)
Lukishova, Svetlana G.; Liapis, Andreas C.; Bissell, Luke J.; Gehring, George M.; Winkler, Justin M.; Boyd, Robert W.
2015-03-01
We present here our results on using liquid crystals in experiments with nonclassical light sources: (1) single-photon sources exhibiting antibunching (separation of all photons in time), which are key components for secure quantum communication systems, and (2) entangled photon source with photons exhibiting quantum interference in a Hong-Ou- Mandel interferometer. In the first part, cholesteric liquid crystal hosts were used to create definite circular polarization of antibunched photons emitted by nanocrystal quantum dots. If the photon has unknown polarization, filtering it through a polarizer to produce the desired polarization for quantum key distribution with bits based on polarization states of photons will reduce by half the efficiency of a quantum cryptography system. In the first part, we also provide our results on observation of a circular polarized microcavity resonance in nanocrystal quantum dot fluorescence in a 1-D chiral photonic bandgap cholesteric liquid crystal microcavity. In the second part of this paper with indistinguishable, time-entangled photons, we demonstrate our experimental results on simulating quantum-mechanical barrier tunnelling phenomena. A Hong-Ou-Mandel dip (quantum interference effect) is shifted when a phase change was introduced on the way of one of entangled photons in pair (one arm of the interferometer) by inserting in this arm an electrically controlled planar-aligned nematic liquid crystal layer between two prisms in the conditions close to a frustrated total internal reflection. By applying different AC-voltages to the planar-aligned nematic layer and changing its refractive index, we can obtain various conditions for incident photon propagation - from total reflection to total transmission. Measuring changes of tunnelling times of photon through this structure with femtosecond resolution permitted us to answer some unresolved questions in quantum-mechanical barrier tunnelling phenomena.
Single cell magnetic imaging using a quantum diamond microscope
Park, H.; Weissleder, R.; Yacoby, A.; Lukin, M. D.; Lee, H.; Walsworth, R. L.; Connolly, C. B.
2015-01-01
We apply a quantum diamond microscope to detection and imaging of immunomagnetically labeled cells. This instrument uses nitrogen-vacancy (NV) centers in diamond for correlated magnetic and fluorescence imaging. Our device provides single-cell resolution and two orders of magnitude larger field of view (~1 mm2) than previous NV imaging technologies, enabling practical applications. To illustrate, we quantify cancer biomarkers expressed by rare tumor cells in a large population of healthy cells. PMID:26098019
On the general constraints in single qubit quantum process tomography
Bhandari, Ramesh; Peters, Nicholas A.
2016-05-18
In this study, we briefly review single-qubit quantum process tomography for trace-preserving and nontrace-preserving processes, and derive explicit forms of the general constraints for fitting experimental data. These forms provide additional insight into the structure of the process matrix. We illustrate this with several examples, including a discussion of qubit leakage error models and the intuition which can be gained from their process matrices.
Cryptanalysis of quantum secret sharing with d -level single particles
NASA Astrophysics Data System (ADS)
Lin, Song; Guo, Gong-De; Xu, Yong-Zhen; Sun, Ying; Liu, Xiao-Fen
2016-06-01
In a recent paper [V. Karimipour and M. Asoudeh, Phys. Rev. A 92, 030301(R) (2015)], 10.1103/PhysRevA.92.030301, a multiparty quantum secret-sharing protocol based on d -level single particles was proposed. We discussed the security of this protocol and found that it is not secure for any one dishonest participant who can recover the secret without the aid of other participants.
On the general constraints in single qubit quantum process tomography
Bhandari, Ramesh; Peters, Nicholas A.
2016-01-01
We briefly review single-qubit quantum process tomography for trace-preserving and nontrace-preserving processes, and derive explicit forms of the general constraints for fitting experimental data. These forms provide additional insight into the structure of the process matrix. We illustrate this with several examples, including a discussion of qubit leakage error models and the intuition which can be gained from their process matrices. PMID:27188691
On the general constraints in single qubit quantum process tomography
NASA Astrophysics Data System (ADS)
Bhandari, Ramesh; Peters, Nicholas A.
2016-05-01
We briefly review single-qubit quantum process tomography for trace-preserving and nontrace-preserving processes, and derive explicit forms of the general constraints for fitting experimental data. These forms provide additional insight into the structure of the process matrix. We illustrate this with several examples, including a discussion of qubit leakage error models and the intuition which can be gained from their process matrices.
Quantum memory in a single nucleus in silicon
NASA Astrophysics Data System (ADS)
Freer, Solomon; Simmons, Stephanie; Laucht, Arne; Muhonen, Juha; Dehollain, Juan Pablo; Kalra, Rachpon; Hudson, Fay; Dzurak, Andrew; Itoh, Kohei; McCallum, Jeffrey; Jamieson, David; Morello, Andrea
2015-03-01
Long coherence times and fast manipulation are two desirable qualities of a qubit that for many systems are mutually incompatible. Storing quantum information in an ancillary qubit, i.e. a `quantum memory', is a strategy to address this issue. It is a advantageous property of donor impurities in silicon to have qubits of both qualities in a single lattice site. Here we demonstrate storage and retrieval of quantum information from a single donor electron spin to its host phosphorus nucleus in isotopically-enriched 28Si. We demonstrate a high fidelity memory process characterised via both state and process tomography. We use dynamical decoupling sequences during the nuclear storage to extend the memory time, and demonstrate storage and retrieval of a single qubit of information multiple times before decay. These results underline the inherent versatility and high fidelity of our two qubit system. Funded by the Australian Research Council (CE11E000127) and the U.S. Army Research Office (W911NF-13-1-0024).
Coupling single quantum dots to plasmonic nanocones: optical properties.
Meixner, Alfred J; Jäger, Regina; Jäger, Sebastian; Bräuer, Annika; Scherzinger, Kerstin; Fulmes, Julia; Krockhaus, Sven zur Oven; Gollmer, Dominik A; Kern, Dieter P; Fleischer, Monika
2015-01-01
Coupling a single quantum emitter, such as a fluorescent molecule or a quantum dot (QD), to a plasmonic nanostructure is an important issue in nano-optics and nano-spectroscopy, relevant for a wide range of applications, including tip-enhanced near-field optical microscopy, plasmon enhanced molecular sensing and spectroscopy, and nanophotonic amplifiers or nanolasers, to mention only a few. While the field enhancement of a sharp nanoantenna increasing the excitation rate of a very closely positioned single molecule or QD has been well investigated, the detailed physical mechanisms involved in the emission of a photon from such a system are, by far, less investigated. In one of our ongoing research projects, we try to address these issues by constructing and spectroscopically analysing geometrically simple hybrid heterostructures consisting of sharp gold cones with single quantum dots attached to the very tip apex. An important goal of this work is to tune the longitudinal plasmon resonance by adjusting the cones' geometry to the emission maximum of the core-shell CdSe/ZnS QDs at nominally 650 nm. Luminescence spectra of the bare cones, pure QDs and hybrid systems were distinguished successfully. In the next steps we will further investigate, experimentally and theoretically, the optical properties of the coupled systems in more detail, such as the fluorescence spectra, blinking statistics, and the current results on the fluorescence lifetimes, and compare them with uncoupled QDs to obtain a clearer picture of the radiative and non-radiative processes. PMID:26404008
Blinking suppression of single quantum dots in agarose gel
Ko, H. C.; Yuan, C. T.; Tang, Jau; Lin, S. H.
2010-01-04
Fluorescence blinking is commonly observed in single molecule/particle spectroscopy, but it is an undesirable feature in many applications. We demonstrated that single CdSe/ZnS quantum dots in agarose gel exhibited suppressed blinking behavior. In addition, the long-time exponential bending tail of the power-law blinking statistics was found to be influenced by agarose gel concentration. We suggest that electron transfer from the light state to the dark state might be blocked due to electrostatic surrounding of gel with inherent negatively charged fibers.
Electrically driven single photon emission from a CdSe/ZnSSe single quantum dot at 200 K
Quitsch, Wolf; Kümmell, Tilmar; Bacher, Gerd; Gust, Arne; Kruse, Carsten; Hommel, Detlef
2014-09-01
High temperature operation of an electrically driven single photon emitter based on a single epitaxial quantum dot is reported. CdSe/ZnSSe/MgS quantum dots are embedded into a p-i-n diode architecture providing almost background free excitonic and biexcitonic electroluminescence from individual quantum dots through apertures in the top contacts. Clear antibunching with g{sup 2}(τ = 0) = 0.28 ± 0.20 can be tracked up to T = 200 K, representing the highest temperature for electrically triggered single photon emission from a single quantum dot device.
Multisublevel Magnetoquantum Conductance in Single and Coupled Double Quantum Wires
Lyo, Sungkwun Ken; Huang, Danhong
2001-09-15
We study the ballistic and diffusive magnetoquantum transport using a typical quantum point contact geometry for single and tunnel-coupled double wires that are wide (less than or similar to1 mum) in one perpendicular direction with densely populated sublevels and extremely confined in the other perpendicular (i.e., growth) direction. A general analytic solution to the Boltzmann equation is presented for multisublevel elastic scattering at low temperatures. The solution is employed to study interesting magnetic-field dependent behavior of the conductance such as a large enhancement and quantum oscillations of the conductance for various structures and field orientations. These phenomena originate from the following field-induced properties: magnetic confinement, displacement of the initial- and final-state wave functions for scattering, variation of the Fermi velocities, mass enhancement, depopulation of the sublevels and anticrossing (in double quantum wires). The magnetoconductance is strikingly different in long diffusive (or rough. dirty) wires from the quantized conductance in short ballistic (or clean) wires. Numerical results obtained for the rectangular confinement potentials in the growth direction are satisfactorily interpreted in terms of the analytic solutions based on harmonic confinement potentials. Some of the predicted features of the field-dependent diffusive and quantized conductances are consistent with recent data from GaAs/AlxGa1-xAs double quantum wires.
Individual single-wall carbon nanotubes as quantum wires
NASA Astrophysics Data System (ADS)
Tans, Sander J.; Devoret, Michel H.; Dai, Hongjie; Thess, Andreas; Smalley, Richard E.; Geerligs, L. J.; Dekker, Cees
1997-04-01
Carbon nanotubes have been regarded since their discovery1 as potential molecular quantum wires. In the case of multi-wall nanotubes, where many tubes are arranged in a coaxial fashion, the electrical properties of individual tubes have been shown to vary strongly from tube to tube2,3, and to be characterized by disorder and localization4. Single-wall nanotubes5,6 (SWNTs) have recently been obtained with high yields and structural uniformity7. Particular varieties of these highly symmetric structures have been predicted to be metallic, with electrical conduction occurring through only two electronic modes8-10. Because of the structural symmetry and stiffness of SWNTs, their molecular wavefunctions may extend over the entire tube. Here we report electrical transport measurements on individual single-wall nanotubes that confirm these theoretical predictions. We find that SWNTs indeed act as genuine quantum wires. Electrical conduction seems to occur through well separated, discrete electron states that are quantum-mechanically coherent over long distance, that is at least from contact to contact (140nm). Data in a magnetic field indicate shifting of these states due to the Zeeman effect.
Quantum contextual phenomena observed in single-neutron interferometer experiments
Hasegawa, Yuji; Rauch, Helmut
2006-01-04
Neutron optical experiments are presented, which exhibit quantum contextual phenomena. Entanglement is achieved not between particles, but between degrees of freedom, in this case, for a single-particle. Appropriate combinations of the direction of spin analysis and the position of the phase shifter allow an experimental verification of the violation of a Bell-like inequality. Our experiments manifest the fact that manipulation of the wavefunction in one Hilbert space influences the result of the measurement in the other Hilbert space: manipulation without touch{exclamation_point} Next, we report another experiment which exhibits other peculiarity of quantum contextuality, e.g., originally intended to show a Kochen-Specker-like phenomenon. We have introduced inequalities for quantitative analysis of the experiments. The value obtained in the experiments clearly showed violations of prediction by non-contextual theory. Finally, we have accomplished a tomographic determination of entangled quantum state in single-neutrons. There, characteristics of the Bell-sate are confirmed: four poles for the real part of the density matrix are clearly seen.
Single Electron in Systems of Two and Three Quantum Dots
NASA Astrophysics Data System (ADS)
Filikhin, Igor; Vlahovic, Branislav
We consider the single electron confinement states in the system of two and three quantum dots (QDs). The InAs/GaAs QDs are modeled as laterally distributed dots, using single sub-band effective mass approach with effective potential simulating the strain effect. Electron localization in double quantum dots (DQDs) and in triple quantum dots (TQDs) is studied over the entire electron energy spectrum by varying the geometry parameters of these QDs arrays. It is shown that a small violation of the DQD shape symmetry drastically affects tunneling. This effect also appears as a numerical instability in calculations of spectral distribution of localized/delocalized electron states for small variations of the input parameters of numerical procedure. The effect of adding a third dot to a DQD is investigated. We show that the presence of a third dot increases the tunneling in the initial DQD. The spectral distribution of localized/delocalized states appears sensitive to the violation of the mirror symmetry of TQDs. This work was supported by the NSF (HRD-1345219).
Information-holding quantum router of single photons using natural atom
NASA Astrophysics Data System (ADS)
Yan, Guo-An; Cai, Qing-Yu; Chen, Ai-Xi
2016-04-01
In a quantum network, a quantum router can play a key role that involves exchanging quantum information (quantum states) among different parties. In this paper, we propose a single-photon quantum router by using a four-level atom that is embedded in quantum multi-channels, which are composed of coupled-resonator waveguides. Single photons can be guided from one quantum channel to another by controlling an on-demand classical field. The fidelity of the routing atom recovers to a maximum after a time evolution cycle of the system; thus, the fidelity of the information-carrying single photon reaches unit at the same time. For the first time, we demonstrate that quantum information carried by single photons can be perfectly held after a quantum router.
Wei, Hai-Rui; Deng, Fu-Guo
2014-01-13
We present some compact quantum circuits for a deterministic quantum computing on electron-spin qubits assisted by quantum dots inside single-side optical microcavities, including the CNOT, Toffoli, and Fredkin gates. They are constructed by exploiting the giant optical Faraday rotation induced by a single-electron spin in a quantum dot inside a single-side optical microcavity as a result of cavity quantum electrodynamics. Our universal quantum gates have some advantages. First, all the gates are accomplished with a success probability of 100% in principle. Second, our schemes require no additional electron-spin qubits and they are achieved by some input-output processes of a single photon. Third, our circuits for these gates are simple and economic. Moreover, our devices for these gates work in both the weak coupling and the strong coupling regimes, and they are feasible in experiment. PMID:24515020
Addressing single trapped ions for Rydberg quantum logic
NASA Astrophysics Data System (ADS)
Bachor, P.; Feldker, T.; Walz, J.; Schmidt-Kaler, F.
2016-08-01
We demonstrate the excitation of ions to the Rydberg state 22F by vacuum ultraviolet radiation at a wavelength of 123 nm combined with the coherent manipulation of the optical qubit transition in {}40{{Ca}}+. With a tightly focused beam at 729 nm wavelength we coherently excite a single ion from a linear string into the metastable 3{D}5/2 state before a VUV pulse excites it to the Rydberg state. In combination with ion shuttling in the trap, we extend this approach to the addressed excitation of multiple ions. The coherent initialization as well as the addressed Rydberg excitation are key prerequisites for more complex applications of Rydberg ions in quantum simulation or quantum information processing.
Single-quantum dot imaging with a photon counting camera
Michalet, X.; Colyer, R. A.; Antelman, J.; Siegmund, O.H.W.; Tremsin, A.; Vallerga, J.V.; Weiss, S.
2010-01-01
The expanding spectrum of applications of single-molecule fluorescence imaging ranges from fundamental in vitro studies of biomolecular activity to tracking of receptors in live cells. The success of these assays has relied on progresses in organic and non-organic fluorescent probe developments as well as improvements in the sensitivity of light detectors. We describe a new type of detector developed with the specific goal of ultra-sensitive single-molecule imaging. It is a wide-field, photon-counting detector providing high temporal and high spatial resolution information for each incoming photon. It can be used as a standard low-light level camera, but also allows access to a lot more information, such as fluorescence lifetime and spatio-temporal correlations. We illustrate the single-molecule imaging performance of our current prototype using quantum dots and discuss on-going and future developments of this detector. PMID:19689323
Quantum-Sequencing: Fast electronic single DNA molecule sequencing
NASA Astrophysics Data System (ADS)
Casamada Ribot, Josep; Chatterjee, Anushree; Nagpal, Prashant
2014-03-01
A major goal of third-generation sequencing technologies is to develop a fast, reliable, enzyme-free, high-throughput and cost-effective, single-molecule sequencing method. Here, we present the first demonstration of unique ``electronic fingerprint'' of all nucleotides (A, G, T, C), with single-molecule DNA sequencing, using Quantum-tunneling Sequencing (Q-Seq) at room temperature. We show that the electronic state of the nucleobases shift depending on the pH, with most distinct states identified at acidic pH. We also demonstrate identification of single nucleotide modifications (methylation here). Using these unique electronic fingerprints (or tunneling data), we report a partial sequence of beta lactamase (bla) gene, which encodes resistance to beta-lactam antibiotics, with over 95% success rate. These results highlight the potential of Q-Seq as a robust technique for next-generation sequencing.
Quantum Probability Cancellation Due to a Single-Photon State
NASA Technical Reports Server (NTRS)
Ou, Z. Y.
1996-01-01
When an N-photon state enters a lossless symmetric beamsplitter from one input port, the photon distribution for the two output ports has the form of Bernouli Binormial, with highest probability at equal partition (N/2 at one outport and N/2 at the other). However, injection of a single photon state at the other input port can dramatically change the photon distribution at the outputs, resulting in zero probability at equal partition. Such a strong deviation from classical particle theory stems from quantum probability amplitude cancellation. The effect persists even if the N-photon state is replaced by an arbitrary state of light. A special case is the coherent state which corresponds to homodyne detection of a single photon state and can lead to the measurement of the wave function of a single photon state.
Tunable single-mode slot waveguide quantum cascade lasers
Meng, Bo; Tao, Jin; Quan Zeng, Yong; Wu, Sheng; Jie Wang, Qi
2014-05-19
We report experimental demonstration of tunable, monolithic, single-mode quantum cascade lasers (QCLs) at ∼10 μm with a two-section etched slot structure. A single-mode tuning range of 77 cm{sup −1} (785 nm), corresponding to ∼7.8% of the relative tuning range, was realized with a ∼20 dB side mode suppression ratio within the whole tuning range. Compared with integrated distributed feedback QCLs, our devices have the advantages of easy fabrication and a broader tuning range. Further theoretical analyses and numerical simulations show that it is possible to achieve a broad continuous tuning range by optimizing the slot structures. The proposed slot-waveguide design could provide an alternative but simple approach to the existing tuning schemes for realizing broadly continuous tunable single-mode QCLs.
Quantum Dot Platform for Single-Cell Molecular Profiling
NASA Astrophysics Data System (ADS)
Zrazhevskiy, Pavel S.
In-depth understanding of the nature of cell physiology and ability to diagnose and control the progression of pathological processes heavily rely on untangling the complexity of intracellular molecular mechanisms and pathways. Therefore, comprehensive molecular profiling of individual cells within the context of their natural tissue or cell culture microenvironment is essential. In principle, this goal can be achieved by tagging each molecular target with a unique reporter probe and detecting its localization with high sensitivity at sub-cellular resolution, primarily via microscopy-based imaging. Yet, neither widely used conventional methods nor more advanced nanoparticle-based techniques have been able to address this task up to date. High multiplexing potential of fluorescent probes is heavily restrained by the inability to uniquely match probes with corresponding molecular targets. This issue is especially relevant for quantum dot probes---while simultaneous spectral imaging of up to 10 different probes is possible, only few can be used concurrently for staining with existing methods. To fully utilize multiplexing potential of quantum dots, it is necessary to design a new staining platform featuring unique assignment of each target to a corresponding quantum dot probe. This dissertation presents two complementary versatile approaches towards achieving comprehensive single-cell molecular profiling and describes engineering of quantum dot probes specifically tailored for each staining method. Analysis of expanded molecular profiles is achieved through augmenting parallel multiplexing capacity with performing several staining cycles on the same specimen in sequential manner. In contrast to other methods utilizing quantum dots or other nanoparticles, which often involve sophisticated probe synthesis, the platform technology presented here takes advantage of simple covalent bioconjugation and non-covalent self-assembly mechanisms for straightforward probe
Schaibley, J R; Burgers, A P; McCracken, G A; Duan, L-M; Berman, P R; Steel, D G; Bracker, A S; Gammon, D; Sham, L J
2013-04-19
The electron spin state of a singly charged semiconductor quantum dot has been shown to form a suitable single qubit for quantum computing architectures with fast gate times. A key challenge in realizing a useful quantum dot quantum computing architecture lies in demonstrating the ability to scale the system to many qubits. In this Letter, we report an all optical experimental demonstration of quantum entanglement between a single electron spin confined to a single charged semiconductor quantum dot and the polarization state of a photon spontaneously emitted from the quantum dot's excited state. We obtain a lower bound on the fidelity of entanglement of 0.59±0.04, which is 84% of the maximum achievable given the timing resolution of available single photon detectors. In future applications, such as measurement-based spin-spin entanglement which does not require sub-nanosecond timing resolution, we estimate that this system would enable near ideal performance. The inferred (usable) entanglement generation rate is 3×10(3) s(-1). This spin-photon entanglement is the first step to a scalable quantum dot quantum computing architecture relying on photon (flying) qubits to mediate entanglement between distant nodes of a quantum dot network. PMID:23679636
Blok, M S; Kalb, N; Reiserer, A; Taminiau, T H; Hanson, R
2015-01-01
Single defect centers in diamond have emerged as a powerful platform for quantum optics experiments and quantum information processing tasks. Connecting spatially separated nodes via optical photons into a quantum network will enable distributed quantum computing and long-range quantum communication. Initial experiments on trapped atoms and ions as well as defects in diamond have demonstrated entanglement between two nodes over several meters. To realize multi-node networks, additional quantum bit systems that store quantum states while new entanglement links are established are highly desirable. Such memories allow for entanglement distillation, purification and quantum repeater protocols that extend the size, speed and distance of the network. However, to be effective, the memory must be robust against the entanglement generation protocol, which typically must be repeated many times. Here we evaluate the prospects of using carbon nuclear spins in diamond as quantum memories that are compatible with quantum networks based on single nitrogen vacancy (NV) defects in diamond. We present a theoretical framework to describe the dephasing of the nuclear spins under repeated generation of NV spin-photon entanglement and show that quantum states can be stored during hundreds of repetitions using typical experimental coupling parameters. This result demonstrates that nuclear spins with weak hyperfine couplings are promising quantum memories for quantum networks. PMID:26411802
Erber, T.; Hammerling, P.; Hockney, G.; Porrati, M.; Putterman, S.
1989-03-01
When a single trapped /sup 198/Hg/sup +/ ion is illuminated by two lasers,each tuned to an approximate transition, the resulting fluorescence switches/ital on/ and /ital off/ in a series of pulses resembling a bistable telegraph.This intermittent fluorescence can also be obtained by optical pumpingwith a single laser. Quantum jumps between successive atomic levels may betraced directly with multiple-resonance fluorescence. Atomic transition ratesand photon antibunching distributions can be inferred from the pulse statisticsand compared with quantum theory. Stochastic tests also indicate that thequantum telegraphs are good random number generators. During periods whenthe fluorescence is switched /ital off/, the radiationless atomic currentsthat generate the telegraph signals can be adjusted by varying the laserillumination: if this coherent evolution of the wave functions is sustainedover sufficiently long time intervals, novel /ital interactive/ precisionmeasurements, near the limits of the time-energy uncertainty relations, arepossible./copyright/ 1989 Academic Press, Inc.
Pseudomorphic Single-Quantum-Well Lasers Emit At 980 Nm
NASA Technical Reports Server (NTRS)
Larsson, Anders; Forouhar, Siamak; Cody, Jeffrey G.; Lang, Robert J.; Andrekson, Peter A.
1992-01-01
Narrow-stripe semiconductor lasers emitting at 980 nm include pseudomorphic In0.2Ga0.8As/GaAs/AlxGa1-xAs graded-index-of-refraction, separate-confinement-heterostructure single quantum well(GRINSCH SQW) with overlaid ridge waveguide. 980 nm chosen as one that yields most efficient pumping because there is no absorption in excited states at this wavelength. Suitable for pumping Er(Sup3+)-doped optical-fiber amplifiers in optical-fiber communication systems and optical phased-array ranging systems.
Optimised quantum hacking of superconducting nanowire single-photon detectors
NASA Astrophysics Data System (ADS)
Tanner, Michael G.; Makarov, Vadim; Hadfield, Robert H.
2014-03-01
We explore bright-light control of superconducting nanowire single-photon detectors (SNSPDs) in the shunted configuration (a practical measure to avoid latching). In an experiment, we simulate an illumination pattern the SNSPD would receive in a typical quantum key distribution system under hacking attack. We show that it effectively blinds and controls the SNSPD. The transient blinding illumination lasts for a fraction of a microsecond and produces several deterministic fake clicks during this time. This attack does not lead to elevated timing jitter in the spoofed output pulse, and hence does not introduce significant errors. Five different SNSPD chip designs were tested. We consider possible countermeasures to this attack.
Efficient teleportation between remote single-atom quantum memories.
Nölleke, Christian; Neuzner, Andreas; Reiserer, Andreas; Hahn, Carolin; Rempe, Gerhard; Ritter, Stephan
2013-04-01
We demonstrate teleportation of quantum bits between two single atoms in distant laboratories. Using a time-resolved photonic Bell-state measurement, we achieve a teleportation fidelity of (88.0 ± 1.5)%, largely determined by our entanglement fidelity. The low photon collection efficiency in free space is overcome by trapping each atom in an optical cavity. The resulting success probability of 0.1% is almost 5 orders of magnitude larger than in previous experiments with remote material qubits. It is mainly limited by photon propagation and detection losses and can be enhanced with a cavity-based deterministic Bell-state measurement. PMID:25166964
Multi-group dynamic quantum secret sharing with single photons
NASA Astrophysics Data System (ADS)
Liu, Hongwei; Ma, Haiqiang; Wei, Kejin; Yang, Xiuqing; Qu, Wenxiu; Dou, Tianqi; Chen, Yitian; Li, Ruixue; Zhu, Wu
2016-07-01
In this letter, we propose a novel scheme for the realization of single-photon dynamic quantum secret sharing between a boss and three dynamic agent groups. In our system, the boss can not only choose one of these three groups to share the secret with, but also can share two sets of independent keys with two groups without redistribution. Furthermore, the security of communication is enhanced by using a control mode. Compared with previous schemes, our scheme is more flexible and will contribute to a practical application.
Optimised quantum hacking of superconducting nanowire single-photon detectors.
Tanner, Michael G; Makarov, Vadim; Hadfield, Robert H
2014-03-24
We explore bright-light control of superconducting nanowire single-photon detectors (SNSPDs) in the shunted configuration (a practical measure to avoid latching). In an experiment, we simulate an illumination pattern the SNSPD would receive in a typical quantum key distribution system under hacking attack. We show that it effectively blinds and controls the SNSPD. The transient blinding illumination lasts for a fraction of a microsecond and produces several deterministic fake clicks during this time. This attack does not lead to elevated timing jitter in the spoofed output pulse, and hence does not introduce significant errors. Five different SNSPD chip designs were tested. We consider possible countermeasures to this attack. PMID:24664022
Nanoscale optical positioning of single quantum dots for bright and pure single-photon emission
Sapienza, Luca; Davanço, Marcelo; Badolato, Antonio; Srinivasan, Kartik
2015-01-01
Self-assembled, epitaxially grown InAs/GaAs quantum dots (QDs) are promising semiconductor quantum emitters that can be integrated on a chip for a variety of photonic quantum information science applications. However, self-assembled growth results in an essentially random in-plane spatial distribution of QDs, presenting a challenge in creating devices that exploit the strong interaction of single QDs with highly confined optical modes. Here, we present a photoluminescence imaging approach for locating single QDs with respect to alignment features with an average position uncertainty <30 nm (<10 nm when using a solid-immersion lens), which represents an enabling technology for the creation of optimized single QD devices. To that end, we create QD single-photon sources, based on a circular Bragg grating geometry, that simultaneously exhibit high collection efficiency (48%±5% into a 0.4 numerical aperture lens, close to the theoretically predicted value of 50%), low multiphoton probability (g(2)(0) <1%), and a significant Purcell enhancement factor (≈3). PMID:26211442
Nanoscale optical positioning of single quantum dots for bright and pure single-photon emission
NASA Astrophysics Data System (ADS)
Sapienza, Luca; Davanço, Marcelo; Badolato, Antonio; Srinivasan, Kartik
2015-07-01
Self-assembled, epitaxially grown InAs/GaAs quantum dots (QDs) are promising semiconductor quantum emitters that can be integrated on a chip for a variety of photonic quantum information science applications. However, self-assembled growth results in an essentially random in-plane spatial distribution of QDs, presenting a challenge in creating devices that exploit the strong interaction of single QDs with highly confined optical modes. Here, we present a photoluminescence imaging approach for locating single QDs with respect to alignment features with an average position uncertainty <30 nm (<10 nm when using a solid-immersion lens), which represents an enabling technology for the creation of optimized single QD devices. To that end, we create QD single-photon sources, based on a circular Bragg grating geometry, that simultaneously exhibit high collection efficiency (48%+/-5% into a 0.4 numerical aperture lens, close to the theoretically predicted value of 50%), low multiphoton probability (g(2)(0) <1%), and a significant Purcell enhancement factor (~3).
Photonic Quantum Logic with Narrowband Light from Single Atoms
NASA Astrophysics Data System (ADS)
Rubenok, Allison; Holleczek, Annemarie; Barter, Oliver; Dilley, Jerome; Nisbet-Jones, Peter B. R.; Langfahl-Klabes, Gunnar; Kuhn, Axel; Sparrow, Chris; Marshall, Graham D.; O'Brien, Jeremy L.; Poulios, Konstantinos; Matthews, Jonathan C. F.
Atom-cavity sources of narrowband photons are a promising candidate for the future development of quantum technologies. Likewise, integrated photonic circuits have established themselves as a fore-running contender in quantum computing, security, and communication. Here we report on recent achievements to interface these two technologies: Atom-cavity sources coupled to integrated photonic circuits. Using narrow linewidth photons emitted from a single 87 Rb atom strongly coupled to a high-finesse cavity we demonstrate the successful operation of an integrated control-not gate. Furthermore, we are able to verify the generation of post-selected entanglement upon successful operation of the gate. We are able to see non-classical correlations in detection events that are up to three orders of magnitude farther apart than the time needed for light to travel across the chip. Our hybrid approach will facilitate the future development of technologies that benefit from the advantages of both integrated quantum circuits and atom-cavity photon sources. Now at: National Physics Laboratory.
Quantum control and engineering of single spins in diamond
NASA Astrophysics Data System (ADS)
Toyli, David M.
The past two decades have seen intensive research efforts aimed at creating quantum technologies that leverage phenomena such as coherence and entanglement to achieve device functionalities surpassing those attainable with classical physics. While the range of applications for quantum devices is typically limited by their cryogenic operating temperatures, in recent years point defects in semiconductors have emerged as potential candidates for room temperature quantum technologies. In particular, the nitrogen vacancy (NV) center in diamond has gained prominence for the ability to measure and control its spin under ambient conditions and for its potential applications in magnetic sensing. Here we describe experiments that probe the thermal limits to the measurement and control of single NV centers to identify the origin of the system's unique temperature dependence and that define novel thermal sensing applications for single spins. We demonstrate the optical measurement and coherent control of the spin at temperatures exceeding 600 K and show that its addressability is eventually limited by thermal quenching of the optical spin readout. These measurements provide important information for the electronic structure responsible for the optical spin initialization and readout processes and, moreover, suggest that the coherence of the NV center's spin states could be harnessed for thermometry applications. To that end, we develop novel quantum control techniques that selectively probe thermally induced shifts in the spin resonance frequencies while minimizing the defect's interactions with nearby nuclear spins. We use these techniques to extend the NV center's spin coherence for thermometry by 45-fold to achieve thermal sensitivities approaching 10 mK Hz-1/2 . We show the versatility of these techniques by performing measurements in a range of magnetic environments and at temperatures as high as 500 K. Together with diamond's ideal thermal, mechanical, and chemical
Zeros in single-channel transmission through double quantum dots.
Rotter, I; Sadreev, A F
2005-04-01
By using a simple model we consider single-channel transmission through a double quantum dot that consists of two single dots coupled by a wire of finite length L . Each of the two single dots is characterized by a few energy levels only, and the wire is assumed to have only one level whose energy depends on the length L . The transmission is described by using S matrix theory and the effective non-Hermitian Hamilton operator H(eff) of the system. The decay widths of the eigenstates of H(eff) depend strongly on energy. The model explains the origin of the transmission zeros of the double dot that is considered by us. Mostly, they are caused by (destructive) interferences between neighboring levels and are of first order. When, however, both single dots are identical and their transmission zeros are of first order, those of the double dot are of second order. First-order transmission zeros cause phase jumps of the transmission amplitude by pi, while there are no phase jumps related to second-order transmission zeros. In this latter case, a phase jump occurs due to the fact that the width of one of the states vanishes when crossing the energy of the transmission zero. The parameter dependence of the widths of the resonance states is determined by the spectral properties of the two single dots. PMID:15903767
The braided single-stage protocol for quantum secure communication
NASA Astrophysics Data System (ADS)
Darunkar, Bhagyashri; Verma, Pramode K.
2014-05-01
This paper presents the concept and implementation of a Braided Single-stage Protocol for quantum secure communication. The braided single-stage protocol is a multi-photon tolerant secure protocol. This multi-photon tolerant protocol has been implemented in the laboratory using free-space optics technology. The proposed protocol capitalizes on strengths of the three-stage protocol and extends it with a new concept of braiding. This protocol overcomes the limitations associated with the three-stage protocol in the following ways: It uses the transmission channel only once as opposed to three times in the three-stage protocol, and it is invulnerable to man-in-the-middle attack. This paper also presents the error analysis resulting from the misalignment of the devices in the implementation. The experimental results validate the efficient use of transmission resources and improvement in the data transfer rate.
Photon pair source via two coupling single quantum emitters
NASA Astrophysics Data System (ADS)
Peng, Yong-Gang; Zheng, Yu-Jun
2015-10-01
We study the two coupling two-level single molecules driven by an external field as a photon pair source. The probability of emitting two photons, P2, is employed to describe the photon pair source quality in a short time, and the correlation coefficient RAB is employed to describe the photon pair source quality in a long time limit. The results demonstrate that the coupling single quantum emitters can be considered as a stable photon pair source. Project supported by the National Natural Science Foundation of China (Grand Nos. 91021009, 21073110, and 11374191), the Natural Science Foundation of Shandong Province, China (Grant No. ZR2013AQ020), the Postdoctoral Science Foundation of China (Grant No. 2013M531584), the Doctoral Program of Higher Education of China (Grant Nos. 20130131110005 and 20130131120006), and the Taishan Scholarship Project of Shandong Province, China.
Tunable Raman photons in singly charged p -doped quantum dots
NASA Astrophysics Data System (ADS)
Carreño, F.; Antón, M. A.
2016-03-01
The obtention of spontaneous Raman photons is analyzed in singly charged p -doped quantum dots in the absence of an external magnetic field. The use of a far detuned single driving laser allows one to obtain a Raman photon line which exhibits a subnatural linewidth, and whose center can be tuned by changing the detuning and/or the Rabi frequency of the driving field. The Raman photons are produced along the undriven transition and they arise from a weak interaction of the trion states with the nuclear spins. The operating point for the gate voltage of the heterostructure can also be used to modify the linewidth and the peak value of the fluorescent signal.
Single-particle spectroscopic measurements of fluorescent graphene quantum dots.
Xu, Qinfeng; Zhou, Qi; Hua, Zheng; Xue, Qi; Zhang, Chunfeng; Wang, Xiaoyong; Pan, Dengyu; Xiao, Min
2013-12-23
We have performed the first single-particle spectroscopic measurements on individual graphene quantum dots (GQDs) and revealed several intriguing fluorescent phenomena that are otherwise hidden in the optical studies of ensemble GQDs. First, despite noticeable differences in the size and the number of layers from particle to particle, all of the GQDs studied possess almost the same spectral lineshapes and peak positions. Second, GQDs with more layers are normally brighter emitters but are associated with shorter fluorescent lifetimes. Third, the fluorescent spectrum of GQDs was red-shifted upon being aged in air, possibly due to the water desorption effect. Finally, the missing emission of single photons and stable fluorescence without any intermittent behavior were observed from individual GQDs. PMID:24251867
Single donor electronics and quantum functionalities with advanced CMOS technology
NASA Astrophysics Data System (ADS)
Jehl, Xavier; Niquet, Yann-Michel; Sanquer, Marc
2016-03-01
Recent progresses in quantum dots technology allow fundamental studies of single donors in various semiconductor nanostructures. For the prospect of applications figures of merits such as scalability, tunability, and operation at relatively large temperature are of prime importance. Beyond the case of actual dopant atoms in a host crystal, similar arguments hold for small enough quantum dots which behave as artificial atoms, for instance for single spin control and manipulation. In this context, this experimental review focuses on the silicon-on-insulator devices produced within microelectronics facilities with only very minor modifications to the current industrial CMOS process and tools. This is required for scalability and enabled by shallow trench or mesa isolation. It also paves the way for real integration with conventional circuits, as illustrated by a nanoscale device coupled to a CMOS circuit producing a radio-frequency drive on-chip. At the device level we emphasize the central role of electrostatics in etched silicon nanowire transistors, which allows to understand the characteristics in the full range from zero to room temperature.
Construction of a single atom trap for quantum information protocols
NASA Astrophysics Data System (ADS)
Shea, Margaret E.; Baker, Paul M.; Gauthier, Daniel J.; Duke Physics Department Team
2016-05-01
The field of quantum information science addresses outstanding problems such as achieving fundamentally secure communication and solving computationally hard problems. Great progress has been made in the field, particularly using photons coupled to ions and super conducting qubits. Neutral atoms are also interesting for these applications and though the technology for control of neutrals lags behind that of trapped ions, they offer some key advantages: primarily coupling to optical frequencies closer to the telecom band than trapped ions or superconducting qubits. Here we report progress on constructing a single atom trap for 87 Rb. This system is a promising platform for studying the technical problems facing neutral atom quantum computing. For example, most protocols destroy the trap when reading out the neutral atom's state; we will investigate an alternative non-destructive state detection scheme. We detail the experimental systems involved and the challenges addressed in trapping a single atom. All of our hardware components are off the shelf and relatively inexpensive. Unlike many other systems, we place a high numerical aperture lens inside our vacuum system to increase photon collection efficiency. We gratefully acknowledge the financial support of the ARO through Grant # W911NF1520047.
Entanglement-secured single-qubit quantum secret sharing
Scherpelz, P.; Resch, R.; Berryrieser, D.; Lynn, T. W.
2011-09-15
In single-qubit quantum secret sharing, a secret is shared between N parties via manipulation and measurement of one qubit at a time. Each qubit is sent to all N parties in sequence; the secret is encoded in the first participant's preparation of the qubit state and the subsequent participants' choices of state rotation or measurement basis. We present a protocol for single-qubit quantum secret sharing using polarization entanglement of photon pairs produced in type-I spontaneous parametric downconversion. We investigate the protocol's security against eavesdropping attack under common experimental conditions: a lossy channel for photon transmission, and imperfect preparation of the initial qubit state. A protocol which exploits entanglement between photons, rather than simply polarization correlation, is more robustly secure. We implement the entanglement-based secret-sharing protocol with 87% secret-sharing fidelity, limited by the purity of the entangled state produced by our present apparatus. We demonstrate a photon-number splitting eavesdropping attack, which achieves no success against the entanglement-based protocol while showing the predicted rate of success against a correlation-based protocol.
Single donor electronics and quantum functionalities with advanced CMOS technology.
Jehl, Xavier; Niquet, Yann-Michel; Sanquer, Marc
2016-03-16
Recent progresses in quantum dots technology allow fundamental studies of single donors in various semiconductor nanostructures. For the prospect of applications figures of merits such as scalability, tunability, and operation at relatively large temperature are of prime importance. Beyond the case of actual dopant atoms in a host crystal, similar arguments hold for small enough quantum dots which behave as artificial atoms, for instance for single spin control and manipulation. In this context, this experimental review focuses on the silicon-on-insulator devices produced within microelectronics facilities with only very minor modifications to the current industrial CMOS process and tools. This is required for scalability and enabled by shallow trench or mesa isolation. It also paves the way for real integration with conventional circuits, as illustrated by a nanoscale device coupled to a CMOS circuit producing a radio-frequency drive on-chip. At the device level we emphasize the central role of electrostatics in etched silicon nanowire transistors, which allows to understand the characteristics in the full range from zero to room temperature. PMID:26871255
Quantum dot device tunable from single to triple dot system
Rogge, M. C.; Haug, R. J.; Pierz, K.
2013-12-04
We present a lateral quantum dot device which has a tunable number of quantum dots. Depending on easily tunable gate voltages, one, two or three quantum dots are found. They are investigated in transport and charge detection.
Single-copy entanglement in a gapped quantum spin chain.
Hadley, Christopher
2008-05-01
The single-copy entanglement of a given many-body quantum system is defined [J. Eisert and M. Cramer, Phys. Rev. A 72, 042112 (2005)10.1103/PhysRevA.72.042112] as the maximal entanglement deterministically distillable from a bipartition of a single specimen of that system. For critical (gapless) spin chains, it was recently shown that this is exactly half the von Neumann entropy [R. Orús, J. I. Latorre, J. Eisert, and M. Cramer, Phys. Rev. A 73, 060303(R) (2006)], itself defined as the entanglement distillable in the asymptotic limit-i.e., given an infinite number of copies of the system. It is an open question as to what the equivalent behavior for gapped systems is. In this Letter, I show that for the paradigmatic spin-S Affleck-Kennedy-Lieb-Tasaki chain (the archetypal gapped chain), the single-copy entanglement is equal to the von Neumann entropy; i.e., all the entanglement present may be distilled from a single specimen. PMID:18518329
Single atom detection in ultracold quantum gases: a review of current progress.
Ott, Herwig
2016-05-01
The recent advances in single atom detection and manipulation in experiments with ultracold quantum gases are reviewed. The discussion starts with the basic principles of trapping, cooling and detecting single ions and atoms. The realization of single atom detection in ultracold quantum gases is presented in detail and the employed methods, which are based on light scattering, electron scattering, field ionization and direct neutral particle detection are discussed. The microscopic coherent manipulation of single atoms in a quantum gas is also covered. Various examples are given in order to highlight the power of these approaches to study many-body quantum systems. PMID:27093632
Single atom detection in ultracold quantum gases: a review of current progress
NASA Astrophysics Data System (ADS)
Ott, Herwig
2016-05-01
The recent advances in single atom detection and manipulation in experiments with ultracold quantum gases are reviewed. The discussion starts with the basic principles of trapping, cooling and detecting single ions and atoms. The realization of single atom detection in ultracold quantum gases is presented in detail and the employed methods, which are based on light scattering, electron scattering, field ionization and direct neutral particle detection are discussed. The microscopic coherent manipulation of single atoms in a quantum gas is also covered. Various examples are given in order to highlight the power of these approaches to study many-body quantum systems.
NASA Astrophysics Data System (ADS)
Castelletto, S. A.; Scholten, R. E.
2008-03-01
Single photon counting, based on single photon sources and detectors, is a key ingredient for certain applications aiming at new quantum information technologies. Quantum cryptography, quantum radiometry, distributed quantum computing, as well as adjacent technologies such as biomedical and astronomical imaging, and low power classical communication also rely on single-photon technology. This paper reviews the present status of single photon sources and related counting measurement techniques, based on correlated (or heralded) photons in parametric down-conversion, and their possible impact on the above mentioned technologies, as well as an assessment for photon standards in the future.
Three coupled qubits in a single superconducting quantum circuit
NASA Astrophysics Data System (ADS)
Chand, Madhavi; Kundu, Suman; Nehra, N.; Raj, Cosmic; Roy, Tanay; Ranadive, A.; Patankar, Meghan P.; Vijay, R.
We propose a new design for a 3-qubit system in the 3D circuit QED architecture. Our design exploits the geometrical symmetry of a single superconducting circuit with three degrees of freedom to generate three coupled qubits. However, only one of these is strongly coupled to the environment while the other two are protected from the Purcell effect. Nevertheless, all three qubits can be measured using the standard dispersive technique. We will present preliminary data on this circuit showing evidence of three distinct qubits that retain the essential properties of a 3D transmon, namely insensitivity to charge noise, sufficient anharmonicity and good coherence times. We will also characterize the coupling of the three qubits to each other, to the environment and to a neighboring transmon qubit. Finally, we will compare our design to previous multi-qubit circuits and discuss possible applications in quantum computing and quantum simulations. Funding: Department of Atomic Energy, Govt. of India; Department of Science and Technology, Govt. of India.
Protocols for a quantum network based on single photons
NASA Astrophysics Data System (ADS)
Blum, Susanne; O'Brien, Christopher; Reich, Daniel; Lauk, Nikolai; Koch, Christiane; Fleischhauer, Michael; Morigi, Giovanna
2015-03-01
Two protocols for interfacing single optical photons with individual qubits are theoretically discussed. The first is a protocol which allows one to interface a single optical photon with a superconducting qubit. It makes use of a a spin ensemble, where the individual emitters possess both an optical and a magnetic dipole transition. Reversible frequency conversion is realized by combining optical photon storage, for instance by means of EIT, with the controlled switching on and off the coupling of the magnetic dipole transition with a microwave cavity, which in turn couples to a superconducting qubit. We test various strategies and compare their efficiencies in terms of robustness and transfer time. The second protocol aims at achieving perfect absorption of a photon by a single trapped atom, or solid-state emitter, by means of optimal control theory. We make use of the Krotov algorithm for the purpose of identifying pulses driving the atom, that maximize the efficiency and fidelity of absorption in the setup of. These protocols contribute to the development of a toolbox for quantum networks using hybrid platforms.
Quantum dot imaging platform for single-cell molecular profiling
NASA Astrophysics Data System (ADS)
Zrazhevskiy, Pavel; Gao, Xiaohu
2013-03-01
Study of normal cell physiology and disease pathogenesis heavily relies on untangling the complexity of intracellular molecular mechanisms and pathways. To achieve this goal, comprehensive molecular profiling of individual cells within the context of microenvironment is required. Here we report the development of a multicolour multicycle in situ imaging technology capable of creating detailed quantitative molecular profiles for individual cells at the resolution of optical imaging. A library of stoichiometric fluorescent probes is prepared by linking target-specific antibodies to a universal quantum dot-based platform via protein A in a quick and simple procedure. Surprisingly, despite the potential for multivalent binding between protein A and antibody and the intermediate affinity of this non-covalent bond, fully assembled probes do not aggregate or exchange antibodies, facilitating highly multiplexed parallel staining. This single-cell molecular profiling technology is expected to open new opportunities in systems biology, gene expression studies, signalling pathway analysis and molecular diagnostics.
Quantum wire hybridized with a single-level impurity.
Lerner, Igor V; Yudson, Vladimir I; Yurkevich, Igor V
2008-06-27
We have studied low-temperature properties of interacting electrons in a one-dimensional quantum wire (Luttinger liquid) side-hybridized with a single-level impurity. The hybridization induces a backscattering of electrons in the wire which strongly affects its low-energy properties. Using a one-loop renormalization group approach valid for a weak electron-electron interaction, we have calculated a transmission coefficient through the wire, T(epsilon), and a local density of states, nu(epsilon) at low energies epsilon. In particular, we have found that the antiresonance in T(epsilon) has a generalized Breit-Wigner shape with the effective width Gamma(epsilon) which diverges at the Fermi level. PMID:18643692
Harsij, Zeynab Mirza, Behrouz
2014-12-15
A helicity entangled tripartite state is considered in which the degree of entanglement is preserved in non-inertial frames. It is shown that Quantum Entanglement remains observer independent. As another measure of quantum correlation, Quantum Discord has been investigated. It is explicitly shown that acceleration has no effect on the degree of quantum correlation for the bipartite and tripartite helicity entangled states. Geometric Quantum Discord as a Hilbert–Schmidt distance is computed for helicity entangled states. It is shown that living in non-inertial frames does not make any influence on this distance, either. In addition, the analysis has been extended beyond single mode approximation to show that acceleration does not have any impact on the quantum features in the limit beyond the single mode. As an interesting result, while the density matrix depends on the right and left Unruh modes, the Negativity as a measure of Quantum Entanglement remains constant. Also, Quantum Discord does not change beyond single mode approximation. - Highlights: • The helicity entangled states here are observer independent in non-inertial frames. • It is explicitly shown that Quantum Discord for these states is observer independent. • Geometric Quantum Discord is also not affected by acceleration increase. • Extending to beyond single mode does not change the degree of entanglement. • Beyond single mode approximation the degree of Quantum Discord is also preserved.
Quantum Optical Control of Single Spins in Diamond
NASA Astrophysics Data System (ADS)
Yale, Christopher Gordon
The nitrogen-vacancy (NV) center in diamond has garnered great interest over the past decade as its electronic spin shows promise as a quantum bit (qubit) and nanoscale sensor. Consisting of a substitutional nitrogen adjacent to a vacant site within the carbon lattice of diamond, this defect exhibits millisecond-long spin coherence times extending beyond room temperature, spin-dependent optical addressability, coupling to intrinsic and nearby nuclear spins, and it can be controlled and manipulated through electrical, magnetic, and optical means. In particular, at cryogenic temperatures (T < 25 K), the NV center's excited state becomes sharp and optically resolvable, providing a solid-state quantum optical testbed. In this thesis, I describe several experiments that explore this quantum optical interface to facilitate the development of a photonic network of single spins linked and controlled by light. We begin by exploring how electric fields tune the orbital levels within the NV center through the DC Stark effect, finding a surprising photo-induced field that aids in the ability to tune multiple NV centers' optical transitions to degeneracy. We then develop techniques to fully control the spin state of the NV center by coupling through a lambda system, an energy configuration consisting of two lower levels coupled to one of higher energy. When a lambda system is optically driven, the spin becomes trapped in a dark state, or the eigenstate of the system that is not coupled to the light fields through destructive interference, forming the basis for the various types of control demonstrated. We demonstrate arbitrary-basis initialization and readout of the spin state through coherent population trapping, as well as the ability to rotate about any arbitrary basis through stimulated Raman transitions. Combining these techniques, we measure the NV center's spin coherence through a completely optical measurement. We then extend these lambda system techniques to
Single Electron Charging and Quantum Effects in Semiconductor Nanostructures
NASA Astrophysics Data System (ADS)
Foxman, Ethan Bradley
1993-01-01
We present an experimental study of a small region (~0.3 times 0.3 mum^2) of two-dimensional electron gas in a GaAs/rm Al_{x}Ga_{1-x}As heterostructure. The small electron gas is coupled to electrical leads through tunnel barriers formed by negatively biased Schottky gates on the surface of the heterostructure. Electron transport is studied as a function of gate voltage, magnetic field, temperature, bias voltage and tunneling barrier height. We observe a rich interplay between single electron charging and quantum effects. The conductance of such systems was known to consist of a series of nearly periodic conductance peaks.^{1,2} We further investigate this behavior and show that our observations are consistent with a model that synthesizes classical single electron charging and a discrete tunneling density of states.^{3,4}. We investigate the nature and origin of this tunneling density of states. The spectrum of states is determined through current-voltage measurements and low-bias conductance measurements. The tunneling density of states is mapped as a function of gate voltage and magnetic field. In the latter case, we show that our observations can be understood through a self-consistent model of single electron charging in the quantum Hall regime.^5. Lastly, we report conductance measurements in the regime where the conductance across the tunnel barriers separating the small electron gas from its leads becomes of order e^2/h. We observe that in this regime single electron charging effects are quenched. This effect is shown to arise from an increased capacitance across one of the barriers and from the increased lifetime broadening of states in the small electron gas. ^6 (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.) ftn^1J. H. F. Scott -Thomas, S. B. Field, M. A. Kastner, H. I. Smith, and D. A. Antoniadis, Phys. Rev. Lett. 62, 583 (1989). ^2U. Meirav, M. A. Kastner, and S. J. Wind
Lukishova, S.G.; Knox, R.P.; Freivald, P.; McNamara, A.; Boyd, R.W.; Stroud, Jr., C.R.; Schmid, A.W.; Marshall, K.L.
2006-08-18
This paper describes a new application for liquid crystals: quantum information technology. A deterministically polarized single-photon source that efficiently produces photons exhibiting antibunching is a pivotal hardware element in absolutely secure quantum communication. Planar-aligned nematic liquid crystal hosts deterministically align the single dye molecules which produce deterministically polarized single (antibunched) photons. In addition, 1-D photonic bandgap cholesteric liquid crystals will increase single-photon source efficiency. The experiments and challenges in the observation of deterministically polarized fluorescence from single dye molecules in planar-aligned glassy nematic-liquid-crystal oligomer as well as photon antibunching in glassy cholesteric oligomer are described for the first time.
Compact Quantum Dots for Single-molecule Imaging
Smith, Andrew M.; Nie, Shuming
2012-01-01
Single-molecule imaging is an important tool for understanding the mechanisms of biomolecular function and for visualizing the spatial and temporal heterogeneity of molecular behaviors that underlie cellular biology 1-4. To image an individual molecule of interest, it is typically conjugated to a fluorescent tag (dye, protein, bead, or quantum dot) and observed with epifluorescence or total internal reflection fluorescence (TIRF) microscopy. While dyes and fluorescent proteins have been the mainstay of fluorescence imaging for decades, their fluorescence is unstable under high photon fluxes necessary to observe individual molecules, yielding only a few seconds of observation before complete loss of signal. Latex beads and dye-labeled beads provide improved signal stability but at the expense of drastically larger hydrodynamic size, which can deleteriously alter the diffusion and behavior of the molecule under study. Quantum dots (QDs) offer a balance between these two problematic regimes. These nanoparticles are composed of semiconductor materials and can be engineered with a hydrodynamically compact size with exceptional resistance to photodegradation 5. Thus in recent years QDs have been instrumental in enabling long-term observation of complex macromolecular behavior on the single molecule level. However these particles have still been found to exhibit impaired diffusion in crowded molecular environments such as the cellular cytoplasm and the neuronal synaptic cleft, where their sizes are still too large 4,6,7. Recently we have engineered the cores and surface coatings of QDs for minimized hydrodynamic size, while balancing offsets to colloidal stability, photostability, brightness, and nonspecific binding that have hindered the utility of compact QDs in the past 8,9. The goal of this article is to demonstrate the synthesis, modification, and characterization of these optimized nanocrystals, composed of an alloyed HgxCd1-xSe core coated with an insulating CdyZn1
NASA Astrophysics Data System (ADS)
Zhu, Chang-Hua; Cao, Xin; Quan, Dong-Xiao; Pei, Chang-Xing
2014-08-01
Linear optical quantum Fredkin gate can be applied to quantum computing and quantum multi-user communication networks. In the existing linear optical scheme, two single photon detectors (SPDs) are used to herald the success of the quantum Fredkin gate while they have no photon count. But analysis results show that for non-perfect SPD, the lower the detector efficiency, the higher the heralded success rate by this scheme is. We propose an improved linear optical quantum Fredkin gate by designing a new heralding scheme with an auxiliary qubit and only one SPD, in which the higher the detection efficiency of the heralding detector, the higher the success rate of the gate is. The new heralding scheme can also work efficiently under a non-ideal single photon source. Based on this quantum Fredkin gate, large-scale quantum switching networks can be built. As an example, a quantum Beneš network is shown in which only one SPD is used.
Quantum computing over long time scales in a singly charged quantum dot
NASA Astrophysics Data System (ADS)
Sun, Bo
In this thesis, we will study the continuous wave optical spectroscopy of self-assembled quantum dots (SAQDs), focusing on the use of these dots toward quantum computing and information processing applications. Probing the strong field interaction between an intense optical pump beam and a neutral quantum dot will reveal Autler-Townes splitting and Mollow absorption spectrum. The presence of these two phenomenon confirm the isolated nature of the exciton trapped in the quantum dot and the suppression of many-body physics due to exciton confinement. This curbs the decoherence caused by exciton-exciton interactions in higher dimensional heterostructures. After confirming the atom-like nature of the SAQD, we then charge the SAQD with a single electron and use the electron spin as our qubit. By applying a magnetic field perpendicular to the sample growth direction, we turn on the spin flip Raman transitions and create two lambda (Λ) systems that can be used to coherently manipulate the spin. A single laser resonant with one of the transitions can quickly initialize the spin state via optical pumping while two lasers, one on each leg of the lambda, can initialize the spin into an arbitrary superposition state through coherent population trapping. The developed dark state spectroscopy is then used to demonstrate interaction between the optically generated hole spin with the background nuclear spins. This hole assisted dynamic nuclear polarization creates a feedback mechanism which locks the nuclear field to the laser detunings and suppresses nuclear spin fluctuations. We use dark state spectroscopy to measure a two orders of magnitude increase of the electron spin coherence time, a result of the narrowing of the nuclear field distribution. Furthermore, we find that this nuclear spin narrowing can persist in the dark, without laser interaction, for well over 1s even in the presence of a fluctuating electron charge and electron spin polarization. We have opened the door
Single-dot optical emission from ultralow density well-isolated InP quantum dots
Ugur, A.; Hatami, F.; Masselink, W. T.; Vamivakas, A. N.; Lombez, L.; Atatuere, M.
2008-10-06
We demonstrate a straightforward way to obtain single well-isolated quantum dots emitting in the visible part of the spectrum and characterize the optical emission from single quantum dots using this method. Self-assembled InP quantum dots are grown using gas-source molecular-beam epitaxy over a wide range of InP deposition rates, using an ultralow growth rate of about 0.01 atomic monolayers/s, a quantum-dot density of 1 dot/{mu}m{sup 2} is realized. The resulting isolated InP quantum dots embedded in an InGaP matrix are individually characterized without the need for lithographical patterning and masks on the substrate. Such low-density quantum dots show excitonic emission at around 670 nm with a linewidth limited by instrument resolution. This system is applicable as a single-photon source for applications such as quantum cryptography.
Single InAs quantum dot coupled to different 'environments' in one wafer for quantum photonics
Yu, Ying; Shang, Xiang-Jun; Li, Mi-Feng; Zha, Guo-Wei; Xu, Jian-Xing; Wang, Li-Juan; Wang, Guo-Wei; Ni, Hai-Qiao; Dou, Xiuming; Sun, Baoquan; Niu, Zhi-Chuan
2013-05-20
Self assembled small InAs quantum dots (SQDs) were formed in various densities and environments using gradient InAs deposition on a non-rotating GaAs substrate. Two SQD environments (SQD I and SQD II) were characterized. SQD I featured SQDs surrounded by large QDs, and SQD II featured individual SQDs in the wetting layer (WL). Micro-photoluminescence of single QDs embedded in a cavity under various excitation powers and electric fields gave insight into carrier transport processes. Potential fluctuations of the WL in SQD II, induced by charge redistribution, show promise for charge-tunable QD devices; SQD I shows higher luminescence intensity as a single-photon source.
Quantum Random Access Codes Using Single d -Level Systems
NASA Astrophysics Data System (ADS)
Tavakoli, Armin; Hameedi, Alley; Marques, Breno; Bourennane, Mohamed
2015-05-01
Random access codes (RACs) are used by a party to, with limited communication, access an arbitrary subset of information held by another party. Quantum resources are known to enable RACs that break classical limitations. Here, we study quantum and classical RACs with high-level communication. We derive average performances of classical RACs and present families of high-level quantum RACs. Our results show that high-level quantum systems can significantly increase the advantage of quantum RACs over their classical counterparts. We demonstrate our findings in an experimental realization of a quantum RAC with four-level communication.
Quantum fluctuations and coherence in high-precision single-electron capture.
Kashcheyevs, Vyacheslavs; Timoshenko, Janis
2012-11-21
The phase of a single quantum state is undefined unless the history of its creation provides a reference point. Thus, quantum interference may seem hardly relevant for the design of deterministic single-electron sources which strive to isolate individual charge carriers quickly and completely. We provide a counterexample by analyzing the nonadiabatic separation of a localized quantum state from a Fermi sea due to a closing tunnel barrier. We identify the relevant energy scales and suggest ways to separate the contributions of quantum nonadiabatic excitation and back tunneling to the rare noncapture events. In the optimal regime of balanced decay and nonadiabaticity, our simple electron trap turns into a single-lead Landau-Zener back tunneling interferometer, revealing the dynamical phase accumulated between the particle capture and leakage. The predicted "quantum beats in back tunneling" may turn the error of a single-electron source into a valuable signal revealing essentially nonadiabatic energy scales of a dynamic quantum dot. PMID:23215606
Single Molecule Analysis of Serotonin Transporter Regulation Using Quantum Dots
NASA Astrophysics Data System (ADS)
Chang, Jerry; Tomlinson, Ian; Warnement, Michael; Ustione, Alessandro; Carneiro, Ana; Piston, David; Blakely, Randy; Rosenthal, Sandra
2011-03-01
For the first time, we implement a novel, single molecule approach to define the localization and mobility of the brain's major target of widely prescribed antidepressant medications, the serotonin transporter (SERT). SERT labeled with single quantum dot (Qdot) revealed unsuspected features of transporter mobility with cholesterol-enriched membrane microdomains (often referred to as ``lipid rafts'') and cytoskeleton network linked to transporter activation. We document two pools of surface SERT proteins defined by their lateral mobility, one that exhibits relatively free diffusion in the plasma membrane and a second that displays significantly restricted mobility and localizes to cholesterol-enriched microdomains. Diffusion model prediction and instantaneous velocity analysis indicated that stimuli that act through p38 MAPK-dependent signaling pathways to activate SERT trigger rapid SERT movements within membrane microdomains. Cytoskeleton disruption showed that SERT lateral mobility behaves a membrane raft-constrained, cytoskeleton-associated manner. Our results identify an unsuspected aspect of neurotransmitter transporter regulation that we propose reflects the dissociation of inhibitory, SERT-associated cytoskeletal anchors.
Quantum dots for quantitative imaging: from single molecules to tissue.
Vu, Tania Q; Lam, Wai Yan; Hatch, Ellen W; Lidke, Diane S
2015-04-01
Since their introduction to biological imaging, quantum dots (QDs) have progressed from a little known, but attractive, technology to one that has gained broad application in many areas of biology. The versatile properties of these fluorescent nanoparticles have allowed investigators to conduct biological studies with extended spatiotemporal capabilities that were previously not possible. In this review, we focus on QD applications that provide enhanced quantitative information concerning protein dynamics and localization, including single particle tracking and immunohistochemistry, and finish by examining the prospects of upcoming applications, such as correlative light and electron microscopy and super-resolution. Advances in single molecule imaging, including multi-color and three-dimensional QD tracking, have provided new insights into the mechanisms of cell signaling and protein trafficking. New forms of QD tracking in vivo have allowed the observation of biological processes at molecular level resolution in the physiological context of the whole animal. Further methodological development of multiplexed QD-based immunohistochemistry assays should enable more quantitative analysis of key proteins in tissue samples. These advances highlight the unique quantitative data sets that QDs can provide to further our understanding of biological and disease processes. PMID:25620410
A triple quantum dot in a single-wall carbon nanotube.
Grove-Rasmussen, K; Jørgensen, H I; Hayashi, T; Lindelof, P E; Fujisawa, T
2008-04-01
A top-gated single-wall carbon nanotube is used to define three coupled quantum dots in series between two electrodes. The additional electron number on each quantum dot is controlled by top-gate voltages allowing for current measurements of single, double, and triple quantum dot stability diagrams. Simulations using a capacitor model including tunnel coupling between neighboring dots captures the observed behavior with good agreement. Furthermore, anticrossings between indirectly coupled levels and higher order cotunneling are discussed. PMID:18314966
Electrically pumped single-photon emission at room temperature from a single InGaN/GaN quantum dot
Deshpande, Saniya; Frost, Thomas; Hazari, Arnab; Bhattacharya, Pallab
2014-10-06
We demonstrate a semiconductor quantum dot based electrically pumped single-photon source operating at room temperature. Single photons emitted in the red spectral range from single In{sub 0.4}Ga{sub 0.6}N/GaN quantum dots exhibit a second-order correlation value g{sup (2)}(0) of 0.29, and fast recombination lifetime ∼1.3 ±0.3 ns at room temperature. The single-photon source can be driven at an excitation repetition rate of 200 MHz.
Relaxation time mapping of single quantum dots and substrate background fluorescence
NASA Astrophysics Data System (ADS)
Pshenay-Severin, E.; Mukhin, I.; Fasold, S.; Geiss, R.; Steinbrück, A.; Grange, R.; Chipouline, A.; Pertsch, T.
2015-08-01
We experimentally investigated the role of background signal in time resolved photoluminescence experiments with single quantum dots on substrates. We show that the background fluorescence signal from thin gold films fabricated by electron-beam evaporation and from Al2O3 layers fabricated by atomic layer deposition have to be taken into consideration in experiments on the single photon level. Though all investigated components can be distinguished by their photoluminescence decay rates, the presence of the background signal prevents the observation of photon antibunching from single quantum dots. Moreover, a single quantum dot acts as a hot spot enabling the plasmon supported fluorescence enhancement of gold.
On-chip interference of single photons from an embedded quantum dot and an external laser
NASA Astrophysics Data System (ADS)
Prtljaga, N.; Bentham, C.; O'Hara, J.; Royall, B.; Clarke, E.; Wilson, L. R.; Skolnick, M. S.; Fox, A. M.
2016-06-01
In this work, we demonstrate the on-chip two-photon interference between single photons emitted by a single self-assembled InGaAs quantum dot and an external laser. The quantum dot is embedded within one arm of an air-clad directional coupler which acts as a beam-splitter for incoming light. Photons originating from an attenuated external laser are coupled to the second arm of the beam-splitter and then combined with the quantum dot photons, giving rise to two-photon quantum interference between dissimilar sources. We verify the occurrence of on-chip Hong-Ou-Mandel interference by cross-correlating the optical signal from the separate output ports of the directional coupler. This experimental approach allows us to use a classical light source (laser) to assess in a single step the overall device performance in the quantum regime and probe quantum dot photon indistinguishability on application realistic time scales.
Single-photon non-linear optics with a quantum dot in a waveguide.
Javadi, A; Söllner, I; Arcari, M; Hansen, S Lindskov; Midolo, L; Mahmoodian, S; Kiršanskė, G; Pregnolato, T; Lee, E H; Song, J D; Stobbe, S; Lodahl, P
2015-01-01
Strong non-linear interactions between photons enable logic operations for both classical and quantum-information technology. Unfortunately, non-linear interactions are usually feeble and therefore all-optical logic gates tend to be inefficient. A quantum emitter deterministically coupled to a propagating mode fundamentally changes the situation, since each photon inevitably interacts with the emitter, and highly correlated many-photon states may be created. Here we show that a single quantum dot in a photonic-crystal waveguide can be used as a giant non-linearity sensitive at the single-photon level. The non-linear response is revealed from the intensity and quantum statistics of the scattered photons, and contains contributions from an entangled photon-photon bound state. The quantum non-linearity will find immediate applications for deterministic Bell-state measurements and single-photon transistors and paves the way to scalable waveguide-based photonic quantum-computing architectures. PMID:26492951
Proposal for a telecom quantum repeater with single atoms in optical cavities
NASA Astrophysics Data System (ADS)
Uphoff, Manuel; Brekenfeld, Manuel; Niemietz, Dominik; Ritter, Stephan; Rempe, Gerhard
2016-05-01
Quantum repeaters hold the promise to enable long-distance quantum communication via entanglement generation over arbitrary distances. Single atoms in optical cavities have been shown to be ideally suited for the experimental realization of many tasks in quantum communication. To utilize these systems for a quantum repeater, it would be desirable to operate them at telecom wavelengths. We propose to use a cascaded scheme employing transitions at telecom wavelengths between excited states of alkali atoms for entanglement generation between a single photon at telecom wavelength and a single atom at the crossing point of two cavity modes. A cavity-assisted quantum gate can be used for entanglement swapping. We estimate the performance of these systems using numerical simulations based on experimental parameters obtained for CO2 laser-machined fiber cavities in our laboratory. Finally, we show that a quantum repeater employing the aforementioned scheme and current technology could outperform corresponding schemes based on direct transmission.
Single-photon non-linear optics with a quantum dot in a waveguide
Javadi, A.; Söllner, I.; Arcari, M.; Hansen, S. Lindskov; Midolo, L.; Mahmoodian, S.; Kiršanskė, G; Pregnolato, T.; Lee, E. H.; Song, J. D.; Stobbe, S.; Lodahl, P.
2015-01-01
Strong non-linear interactions between photons enable logic operations for both classical and quantum-information technology. Unfortunately, non-linear interactions are usually feeble and therefore all-optical logic gates tend to be inefficient. A quantum emitter deterministically coupled to a propagating mode fundamentally changes the situation, since each photon inevitably interacts with the emitter, and highly correlated many-photon states may be created. Here we show that a single quantum dot in a photonic-crystal waveguide can be used as a giant non-linearity sensitive at the single-photon level. The non-linear response is revealed from the intensity and quantum statistics of the scattered photons, and contains contributions from an entangled photon–photon bound state. The quantum non-linearity will find immediate applications for deterministic Bell-state measurements and single-photon transistors and paves the way to scalable waveguide-based photonic quantum-computing architectures. PMID:26492951
Quantum detector tomography of a single-photon frequency upconversion detection system.
Ma, Jianhui; Chen, Xiuliang; Hu, Huiqin; Pan, Haifeng; Wu, E; Zeng, Heping
2016-09-01
We experimentally presented a full quantum detector tomography of a synchronously pumped infrared single-photon frequency upconversion detector. A maximum detection efficiency of 37.6% was achieved at the telecom wavelength of 1558 nm with a background noise about 1.0 × 10^{-3} counts/pulse. The corresponding internal quantum conversion efficiency reached as high as 84.4%. The detector was then systematically characterized at different pump powers to investigate the quantum decoherence behavior. Here the reconstructed positive operator valued measure elements were equivalently illustrated with the Wigner function formalism, where the quantum feature of the detector is manifested by the presence of negative values of the Wigner function. In our experiment, pronounced negativities were attained due to the high detection efficiency and low background noise, explicitly showing the quantum feature of the detector. Such quantum detector could be useful in optical quantum state engineering, quantum information processing and communication. PMID:27607700
Quantum proofs can be verified using only single-qubit measurements
NASA Astrophysics Data System (ADS)
Morimae, Tomoyuki; Nagaj, Daniel; Schuch, Norbert
2016-02-01
Quantum Merlin Arthur (QMA) is the class of problems which, though potentially hard to solve, have a quantum solution that can be verified efficiently using a quantum computer. It thus forms a natural quantum version of the classical complexity class NP (and its probabilistic variant MA, Merlin-Arthur games), where the verifier has only classical computational resources. In this paper, we study what happens when we restrict the quantum resources of the verifier to the bare minimum: individual measurements on single qubits received as they come, one by one. We find that despite this grave restriction, it is still possible to soundly verify any problem in QMA for the verifier with the minimum quantum resources possible, without using any quantum memory or multiqubit operations. We provide two independent proofs of this fact, based on measurement-based quantum computation and the local Hamiltonian problem. The former construction also applies to QMA1, i.e., QMA with one-sided error.
NASA Astrophysics Data System (ADS)
Cultrera, Alessandro; Amato, Giampiero; Boarino, Luca; Lamberti, Carlo
2014-08-01
We developed an integrated system for photo-electrical characterization of materials for sensing applications in strictly controlled environment conditions. The peculiar aspect of this setup is the capability of a fine-tuned gas dosage and a fast dynamic chamber pressure control, coupled with current and voltage sensing within a modified cryostat. To illustrate the capabilities of our system we have characterised both p+-type mesoporous silicon (meso-PS) membranes and nano-crystalline mesoporous titanium dioxide (nc-TiO2) films. In particular, as a main topic is presented a well-resolved characterization of mesoporous silicon electrical conductivity changes induced by presence of ethanol. At low pore filling level adsorbate-shunted conduction is avoided, while dielectric screening effects on frozen doping centres are observable. Beside we presented observation of mesoporous titanium dioxide photo-conductivity as a function of different gas pressure reporting opposite effects of relatively low- and high-pressure regimes. High reproducibility provided by the system is discussed as a final remark.
Hoang, Thang B; Akselrod, Gleb M; Mikkelsen, Maiken H
2016-01-13
Efficient and bright single photon sources at room temperature are critical components for quantum information systems such as quantum key distribution, quantum state teleportation, and quantum computation. However, the intrinsic radiative lifetime of quantum emitters is typically ∼10 ns, which severely limits the maximum single photon emission rate and thus entanglement rates. Here, we demonstrate the regime of ultrafast spontaneous emission (∼10 ps) from a single quantum emitter coupled to a plasmonic nanocavity at room temperature. The nanocavity integrated with a single colloidal semiconductor quantum dot produces a 540-fold decrease in the emission lifetime and a simultaneous 1900-fold increase in the total emission intensity. At the same time, the nanocavity acts as a highly efficient optical antenna directing the emission into a single lobe normal to the surface. This plasmonic platform is a versatile geometry into which a variety of other quantum emitters, such as crystal color centers, can be integrated for directional, room-temperature single photon emission rates exceeding 80 GHz. PMID:26606001
Tracking single viruses infecting their host cells using quantum dots.
Liu, Shu-Lin; Wang, Zhi-Gang; Zhang, Zhi-Ling; Pang, Dai-Wen
2016-03-01
Single-virus tracking (SVT) technique, which uses microscopy to monitor the behaviors of viruses, is a vital tool to study the real-time and in situ infection dynamics and virus-related interactions in live cells. To make SVT a more versatile tool in biological research, the researchers have developed a quantum dot (QD)-based SVT technique, which can be utilized for long-term and highly sensitive tracking in live cells. In this review, we describe the development of a QD-based SVT technique and its biological applications. We first discuss the advantage of QDs as tags in the SVT field by comparing the conventional tags, and then focus on the implementation of QD-based SVT experiments, including the QD labeling strategy, instrumentation, and image analysis method. Next, we elaborate the recent advances of QD-based SVT in the biological field, and mainly emphasize the representative examples to show how to use this technique to acquire more meaningful biological information. PMID:26695711
Quantum transport through single and multilayer icosahedral fullerenes
NASA Astrophysics Data System (ADS)
Lovey, Daniel A.; Romero, Rodolfo H.
2013-10-01
We use a tight-binding Hamiltonian and Green functions methods to calculate the quantum transmission through single-wall fullerenes and bilayered and trilayered onions of icosahedral symmetry attached to metallic leads. The electronic structure of the onion-like fullerenes takes into account the curvature and finite size of the fullerenes layers as well as the strength of the intershell interactions depending on to the number of interacting atom pairs belonging to adjacent shells. Misalignment of the symmetry axes of the concentric iscosahedral shells produces breaking of the level degeneracies of the individual shells, giving rise some narrow quasi-continuum bands instead of the localized discrete peaks of the individual fullerenes. As a result, the transmission function for non symmetrical onions is rapidly varying functions of the Fermi energy. Furthermore, we found that most of the features of the transmission through the onions are due to the electronic structure of the outer shell with additional Fano-like antiresonances arising from coupling with or between the inner shells.
Quantum non-Gaussianity of frequency up-converted single photons.
Baune, Christoph; Schönbeck, Axel; Samblowski, Aiko; Fiurášek, Jaromír; Schnabel, Roman
2014-09-22
Nonclassical states of light are an important resource in today's quantum communication and metrology protocols. Quantum up-conversion of nonclassical states is a promising approach to overcome frequency differences between disparate subsystems within a quantum information network. Here, we present the generation of heralded narrowband single photons at 1550 nm via cavity enhanced spontaneous parametric down-conversion (SPDC) and their subsequent up-conversion to 532 nm. Quantum non-Gaussianity (QNG), which is an important feature for applications in quantum information science, was experimentally certified for the first time in frequency up-converted states. PMID:25321750
Effect of quantum collapse on the distribution of work in driven single molecules.
Chernyak, Vladimir; Mukamel, Shaul
2004-07-23
Two sources of quantum deviations from Jarzynski's celebrated classical relation between the free energy change and the distribution of work are analyzed using an exactly solvable harmonic model: Quantum dynamics retains the Gaussian profile of the distribution and merely gives rise to analytic corrections in variant Planck's over 2pi, whereas quantum measurements (wave function collapse) induce extended power-law tails which fundamentally alter the distribution. These results may be observed in quantum information processing and in experiments involving mechanically or optically driven single quantum objects. PMID:15323799
Single-photon-level quantum image memory based on cold atomic ensembles
Ding, Dong-Sheng; Zhou, Zhi-Yuan; Shi, Bao-Sen; Guo, Guang-Can
2013-01-01
A quantum memory is a key component for quantum networks, which will enable the distribution of quantum information. Its successful development requires storage of single-photon light. Encoding photons with spatial shape through higher-dimensional states significantly increases their information-carrying capability and network capacity. However, constructing such quantum memories is challenging. Here we report the first experimental realization of a true single-photon-carrying orbital angular momentum stored via electromagnetically induced transparency in a cold atomic ensemble. Our experiments show that the non-classical pair correlation between trigger photon and retrieved photon is retained, and the spatial structure of input and retrieved photons exhibits strong similarity. More importantly, we demonstrate that single-photon coherence is preserved during storage. The ability to store spatial structure at the single-photon level opens the possibility for high-dimensional quantum memories. PMID:24084711
Single-photon-level quantum image memory based on cold atomic ensembles
NASA Astrophysics Data System (ADS)
Ding, Dong-Sheng; Zhou, Zhi-Yuan; Shi, Bao-Sen; Guo, Guang-Can
2013-10-01
A quantum memory is a key component for quantum networks, which will enable the distribution of quantum information. Its successful development requires storage of single-photon light. Encoding photons with spatial shape through higher-dimensional states significantly increases their information-carrying capability and network capacity. However, constructing such quantum memories is challenging. Here we report the first experimental realization of a true single-photon-carrying orbital angular momentum stored via electromagnetically induced transparency in a cold atomic ensemble. Our experiments show that the non-classical pair correlation between trigger photon and retrieved photon is retained, and the spatial structure of input and retrieved photons exhibits strong similarity. More importantly, we demonstrate that single-photon coherence is preserved during storage. The ability to store spatial structure at the single-photon level opens the possibility for high-dimensional quantum memories.
Single photon emission from site-controlled InGaN/GaN quantum dots
Zhang, Lei; Hill, Tyler A.; Deng, Hui; Teng, Chu-Hsiang; Lee, Leung-Kway; Ku, Pei-Cheng
2013-11-04
Single photon emission was observed from site-controlled InGaN/GaN quantum dots. The single-photon nature of the emission was verified by the second-order correlation function up to 90 K, the highest temperature to date for site-controlled quantum dots. Micro-photoluminescence study on individual quantum dots showed linearly polarized single exciton emission with a lifetime of a few nanoseconds. The dimensions of these quantum dots were well controlled to the precision of state-of-the-art fabrication technologies, as reflected in the uniformity of their optical properties. The yield of optically active quantum dots was greater than 90%, among which 13%–25% exhibited single photon emission at 10 K.
Semiconductor Quantum Rods as Single Molecule FluorescentBiological Labels
Fu, Aihua; Gu, Weiwei; Boussert, Benjamine; Koski, Kristie; Gerion, Daniele; Manna, Liberato; Le Gros, Mark; Larabell, Carolyn; Alivisatos, A. Paul
2006-05-29
In recent years, semiconductor quantum dots have beenapplied with great advantage in a wide range of biological imagingapplications. The continuing developments in the synthesis of nanoscalematerials and specifically in the area of colloidal semiconductornanocrystals have created an opportunity to generate a next generation ofbiological labels with complementary or in some cases enhanced propertiescompared to colloidal quantum dots. In this paper, we report thedevelopment of rod shaped semiconductor nanocrystals (quantum rods) asnew fluorescent biological labels. We have engineered biocompatiblequantum rods by surface silanization and have applied them fornon-specific cell tracking as well as specific cellular targeting. Theproperties of quantum rods as demonstrated here are enhanced sensitivityand greater resistance for degradation as compared to quantum dots.Quantum rods have many potential applications as biological labels insituations where their properties offer advantages over quantumdots.
NASA Astrophysics Data System (ADS)
Shimizu, Kaoru; Imoto, Nobuyuki
2000-11-01
We propose a single-photon interferometer which provides cryptographic quantum communication equivalent to that obtained using a pair of polarization entangled photon twins as a carrier [Phys. Rev. A 60, 157 (1999)]. Instead of manipulating and measuring the internal states of entangled photon twins, cryptographic quantum communication is possible by manipulating a single photon in an extended interferometer. The use of the single-photon interferometer offers significant experimental advantages compared to our previous approach.
Storage of multiple single-photon pulses emitted from a quantum dot in a solid-state quantum memory
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
Single qudit realization of the Deutsch algorithm using superconducting many-level quantum circuits
NASA Astrophysics Data System (ADS)
Kiktenko, E. O.; Fedorov, A. K.; Strakhov, A. A.; Man'ko, V. I.
2015-07-01
Design of a large-scale quantum computer has paramount importance for science and technologies. We investigate a scheme for realization of quantum algorithms using noncomposite quantum systems, i.e., systems without subsystems. In this framework, n artificially allocated "subsystems" play a role of qubits in n-qubits quantum algorithms. With focus on two-qubit quantum algorithms, we demonstrate a realization of the universal set of gates using a d = 5 single qudit state. Manipulation with an ancillary level in the systems allows effective implementation of operators from U(4) group via operators from SU(5) group. Using a possible experimental realization of such systems through anharmonic superconducting many-level quantum circuits, we present a blueprint for a single qudit realization of the Deutsch algorithm, which generalizes previously studied realization based on the virtual spin representation (Kessel et al., 2002 [9]).
Single-photon router: Implementation of Information-Holding of Quantum States
NASA Astrophysics Data System (ADS)
Yan, Guo-an; Lu, Hua; Chen, Ai-xi
2016-07-01
The quantum router is an indispensable element in the future quantum network. In this study, by calculating the fidelity of the atom, we show that the quantum router proposed by J. Lu et al. (Phys. Rev. A 89, 013805, 2014) achieves quantum information-holding. After the single photon passes through the atom, the fidelity of the atom decreases from the maximum value after a period of time and rises to the maximum value of 1. Even upon changing the size of the classical field, this phenomenon will not disappear, only undergo a cycle change. This means such a single-photon quantum router can be applied experimentally since quantum state can be perfectly held after the routing.
Single-photon router: Implementation of Information-Holding of Quantum States
NASA Astrophysics Data System (ADS)
Yan, Guo-an; Lu, Hua; Chen, Ai-xi
2016-03-01
The quantum router is an indispensable element in the future quantum network. In this study, by calculating the fidelity of the atom, we show that the quantum router proposed by J. Lu et al. (Phys. Rev. A 89, 013805, 2014) achieves quantum information-holding. After the single photon passes through the atom, the fidelity of the atom decreases from the maximum value after a period of time and rises to the maximum value of 1. Even upon changing the size of the classical field, this phenomenon will not disappear, only undergo a cycle change. This means such a single-photon quantum router can be applied experimentally since quantum state can be perfectly held after the routing.
Quantum dot circuits: Single-electron switch and few-electron quantum dots
NASA Astrophysics Data System (ADS)
Chan, Ian Hin-Yun
A strongly capacitively-coupled parallel double quantum dot was studied as a single-electron switch. The double dot was fabricated in a two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure. An electrically-floating coupling gate increased capacitive-coupling between the dots, while an etched trench prevented tunnel-coupling between them. Split Coulomb blockade peaks were observed in each dot, and the Coulomb blockade conductance of the double dot formed a hexagonal pattern characteristic of coupled dots. A fractional peak splitting f = 0.34 was measured, which corresponds to a fractional capacitive-coupling alpha ≡ CINT/CSigma = 0.20. This is an order of magnitude larger than reported for similar lateral quantum dots, and shows that the coupling gate works. The strong capacitive-coupling in our device allowed the charge state of one dot to strongly influence the conductance of the other dot and enabled it to work as a single-electron switch. By moving in a combination of gate voltages, electrons are induced in one dot (the "trigger" dot) only. In response to the change in the charge state, the conductance of the other dot (the "switched" dot) is turned on and off. The abruptness of the conductance switching in gate voltage (the switching lineshape) is determined by how well charge is quantized on the trigger dot, and was found to follow tanh and arctan forms for (respectively) good and poor charge quantization in the trigger dot. A few-electron tunnel-coupled series double dot was studied for possible application to quantum computing. The device was fabricated in a square-well 2DEG in a GaAs/AlGaAs heterostructure. The dots were emptied of electrons in order to define the absolute number of electrons in the dot. Finite bias Coulomb blockade measurements on each dot showed that the last Coulomb blockade diamonds did not close and thus that both dots could be emptied. A three-dimensional conductance measurement of one dot in the one sidegate and the
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.
Nonperturbative quantum solutions to resonant four-wave mixing of two single-photon wave packets
Johnsson, Mattias; Fleischhauer, Michael
2003-08-01
We analyze both analytically and numerically the resonant four-wave mixing of two co-propagating single-photon wave packets. We present analytic expressions for the two-photon wave function, and show that quantum solutions exist which display a shape-preserving oscillatory exchange of excitations between the modes. Potential applications including quantum-information processing are discussed.
The Heteronuclear Single-Quantum Correlation (HSQC) Experiment: Vectors versus Product Operators
ERIC Educational Resources Information Center
de la Vega-Herna´ndez, Karen; Antuch, Manuel
2015-01-01
A vectorial representation of the full sequence of events occurring during the 2D-NMR heteronuclear single-quantum correlation (HSQC) experiment is presented. The proposed vectorial representation conveys an understanding of the magnetization evolution during the HSQC pulse sequence for those who have little or no quantum mechanical background.…
White Electroluminescent Lighting Device Based on a Single Quantum Dot Emitter.
Kim, Jong-Hoon; Jo, Dae-Yeon; Lee, Ki-Heon; Jang, Eun-Pyo; Han, Chang-Yeol; Jo, Jung-Ho; Yang, Heesun
2016-07-01
Using a single emitter of Cu-Ga-S/ZnS quantum dots, all-solution-processed white electroluminescent lighting device that not only exhibits the record quantities of 1007 cd m(-2) in luminance and 1.9% in external quantum efficiency but also possesses satisfactorily high color rendering indices of 83-88 is demonstrated. PMID:27135303
Ultrafast single photon emitting quantum photonic structures based on a nano-obelisk
Kim, Je-Hyung; Ko, Young-Ho; Gong, Su-Hyun; Ko, Suk-Min; Cho, Yong-Hoon
2013-01-01
A key issue in a single photon source is fast and efficient generation of a single photon flux with high light extraction efficiency. Significant progress toward high-efficiency single photon sources has been demonstrated by semiconductor quantum dots, especially using narrow bandgap materials. Meanwhile, there are many obstacles, which restrict the use of wide bandgap semiconductor quantum dots as practical single photon sources in ultraviolet-visible region, despite offering free space communication and miniaturized quantum information circuits. Here we demonstrate a single InGaN quantum dot embedded in an obelisk-shaped GaN nanostructure. The nano-obelisk plays an important role in eliminating dislocations, increasing light extraction, and minimizing a built-in electric field. Based on the nano-obelisks, we observed nonconventional narrow quantum dot emission and positive biexciton binding energy, which are signatures of negligible built-in field in single InGaN quantum dots. This results in efficient and ultrafast single photon generation in the violet color region. PMID:23828558
Correlation spectroscopy of excitons and biexcitons on a single quantum dot
Zwiller, Valery; Jonsson, Per; Blom, Hans; Jeppesen, Soeren; Pistol, Mats-Erik; Samuelson, Lars; Katznelson, A.A.; Kotelnikov, E.Yu.; Evtikhiev, Vadim; Bjoerk, Gunnar
2002-11-01
We report the observation of antibunched emission from single self-assembled InAs quantum dots under various conditions. We have measured the correlation function of the photon emission pertaining to single emission lines from single quantum dots under continuous and pulsed laser excitation, as well as under continuous white light excitation. The measurements were performed under different excitation intensities at liquid helium temperatures on two samples with distinct structures. At higher temperatures (30 K), an antibunching dip was still observed. We have also observed antibunching on a second emission line in the quantum dot spectrum, attributed to the biexciton, demonstrating the possibility of generating photon pairs with a single quantum dot. Polarization correlations on the biexciton and exciton line were also measured in an attempt to generate entangled photon pairs.
Cavity-based quantum networks with single atoms and optical photons
NASA Astrophysics Data System (ADS)
Reiserer, Andreas; Rempe, Gerhard
2015-10-01
Distributed quantum networks will allow users to perform tasks and to interact in ways which are not possible with present-day technology. Their implementation is a key challenge for quantum science and requires the development of stationary quantum nodes that can send and receive as well as store and process quantum information locally. The nodes are connected by quantum channels for flying information carriers, i.e., photons. These channels serve both to directly exchange quantum information between nodes and to distribute entanglement over the whole network. In order to scale such networks to many particles and long distances, an efficient interface between the nodes and the channels is required. This article describes the cavity-based approach to this goal, with an emphasis on experimental systems in which single atoms are trapped in and coupled to optical resonators. Besides being conceptually appealing, this approach is promising for quantum networks on larger scales, as it gives access to long qubit coherence times and high light-matter coupling efficiencies. Thus, it allows one to generate entangled photons on the push of a button, to reversibly map the quantum state of a photon onto an atom, to transfer and teleport quantum states between remote atoms, to entangle distant atoms, to detect optical photons nondestructively, to perform entangling quantum gates between an atom and one or several photons, and even provides a route toward efficient heralded quantum memories for future repeaters. The presented general protocols and the identification of key parameters are applicable to other experimental systems.
Oettl, Anton; Ritter, Stephan; Koehl, Michael; Esslinger, Tilman
2006-06-15
We present and characterize an experimental system in which we achieve the integration of an ultrahigh finesse optical cavity with a Bose-Einstein condensate (BEC). The conceptually novel design of the apparatus for the production of BECs features nested vacuum chambers and an in vacuo magnetic transport configuration. It grants large scale spatial access to the BEC for samples and probes via a modular and exchangeable ''science platform.'' We are able to produce {sup 87}Rb condensates of 5x10{sup 6} atoms and to output couple continuous atom lasers. The cavity is mounted on the science platform on top of a vibration isolation system. The optical cavity works in the strong coupling regime of cavity quantum electrodynamics and serves as a quantum optical detector for single atoms. This system enables us to study atom optics on a single particle level and to further develop the field of quantum atom optics. We describe the technological modules and the operation of the combined BEC cavity apparatus. Its performance is characterized by single atom detection measurements for thermal and quantum degenerate atomic beams. The atom laser provides a fast and controllable supply of atoms coupling with the cavity mode and allows for an efficient study of atom field interactions in the strong coupling regime. Moreover, the high detection efficiency for quantum degenerate atoms distinguishes the cavity as a sensitive and weakly invasive probe for cold atomic clouds.
Quantum teleportation of multiple degrees of freedom of a single photon.
Wang, Xi-Lin; Cai, Xin-Dong; Su, Zu-En; Chen, Ming-Cheng; Wu, Dian; Li, Li; Liu, Nai-Le; Lu, Chao-Yang; Pan, Jian-Wei
2015-02-26
Quantum teleportation provides a 'disembodied' way to transfer quantum states from one object to another at a distant location, assisted by previously shared entangled states and a classical communication channel. As well as being of fundamental interest, teleportation has been recognized as an important element in long-distance quantum communication, distributed quantum networks and measurement-based quantum computation. There have been numerous demonstrations of teleportation in different physical systems such as photons, atoms, ions, electrons and superconducting circuits. All the previous experiments were limited to the teleportation of one degree of freedom only. However, a single quantum particle can naturally possess various degrees of freedom--internal and external--and with coherent coupling among them. A fundamental open challenge is to teleport multiple degrees of freedom simultaneously, which is necessary to describe a quantum particle fully and, therefore, to teleport it intact. Here we demonstrate quantum teleportation of the composite quantum states of a single photon encoded in both spin and orbital angular momentum. We use photon pairs entangled in both degrees of freedom (that is, hyper-entangled) as the quantum channel for teleportation, and develop a method to project and discriminate hyper-entangled Bell states by exploiting probabilistic quantum non-demolition measurement, which can be extended to more degrees of freedom. We verify the teleportation for both spin-orbit product states and hybrid entangled states, and achieve a teleportation fidelity ranging from 0.57 to 0.68, above the classical limit. Our work is a step towards the teleportation of more complex quantum systems, and demonstrates an increase in our technical control of scalable quantum technologies. PMID:25719668
Quantum teleportation of multiple degrees of freedom of a single photon
NASA Astrophysics Data System (ADS)
Wang, Xi-Lin; Cai, Xin-Dong; Su, Zu-En; Chen, Ming-Cheng; Wu, Dian; Li, Li; Liu, Nai-Le; Lu, Chao-Yang; Pan, Jian-Wei
2015-02-01
Quantum teleportation provides a `disembodied' way to transfer quantum states from one object to another at a distant location, assisted by previously shared entangled states and a classical communication channel. As well as being of fundamental interest, teleportation has been recognized as an important element in long-distance quantum communication, distributed quantum networks and measurement-based quantum computation. There have been numerous demonstrations of teleportation in different physical systems such as photons, atoms, ions, electrons and superconducting circuits. All the previous experiments were limited to the teleportation of one degree of freedom only. However, a single quantum particle can naturally possess various degrees of freedom--internal and external--and with coherent coupling among them. A fundamental open challenge is to teleport multiple degrees of freedom simultaneously, which is necessary to describe a quantum particle fully and, therefore, to teleport it intact. Here we demonstrate quantum teleportation of the composite quantum states of a single photon encoded in both spin and orbital angular momentum. We use photon pairs entangled in both degrees of freedom (that is, hyper-entangled) as the quantum channel for teleportation, and develop a method to project and discriminate hyper-entangled Bell states by exploiting probabilistic quantum non-demolition measurement, which can be extended to more degrees of freedom. We verify the teleportation for both spin-orbit product states and hybrid entangled states, and achieve a teleportation fidelity ranging from 0.57 to 0.68, above the classical limit. Our work is a step towards the teleportation of more complex quantum systems, and demonstrates an increase in our technical control of scalable quantum technologies.
Heralded Storage of a Photonic Quantum Bit in a Single Atom
NASA Astrophysics Data System (ADS)
Kalb, Norbert; Reiserer, Andreas; Ritter, Stephan; Rempe, Gerhard
2015-06-01
Combining techniques of cavity quantum electrodynamics, quantum measurement, and quantum feedback, we have realized the heralded transfer of a polarization qubit from a photon onto a single atom with 39% efficiency and 86% fidelity. The reverse process, namely, qubit transfer from the atom onto a given photon, is demonstrated with 88% fidelity and an estimated efficiency of up to 69%. In contrast to previous work based on two-photon interference, our scheme is robust against photon arrival-time jitter and achieves much higher efficiencies. Thus, it constitutes a key step toward the implementation of a long-distance quantum network.
Injection of a single electron from static to moving quantum dots.
Bertrand, Benoit; Hermelin, Sylvain; Mortemousque, Pierre-André; Takada, Shintaro; Yamamoto, Michihisa; Tarucha, Seigo; Ludwig, Arne; Wieck, Andreas D; Bäuerle, Christopher; Meunier, Tristan
2016-05-27
We study the injection mechanism of a single electron from a static quantum dot into a moving quantum dot. The moving quantum dots are created with surface acoustic waves (SAWs) in a long depleted channel. We demonstrate that the injection process is characterized by an activation law with a threshold that depends on the SAW amplitude and on the dot-channel potential gradient. By sufficiently increasing the SAW modulation amplitude, we can reach a regime where the transfer has unity probability and is potentially adiabatic. This study points to the relevant regime to use moving dots in quantum information protocols. PMID:27087057
Quantum Ion-Acoustic Oscillations in Single-Walled Carbon Nanotubes
NASA Astrophysics Data System (ADS)
Khan, S. A.; Iqbal, Z.; Wazir, Z.; Aman-ur-Rehman
2016-05-01
Quantum ion-acoustic oscillations in single-walled carbon nanotubes are studied by employing a quantum hydrodynamics model. The dispersion equation is obtained by Fourier transformation, which exhibits the existence of quantum ion-acoustic wave affected by change of density balance due to presence of positive or negative heavy species as stationary ion clusters and wave potential at equilibrium. The numerical results are presented, and the role of quantum degeneracy, nanotube geometry, electron exchange-correlation effects, and concentration and polarity of heavy species on wave dispersion is pointed out for typical systems of interest.
Distinct quantum states can be compatible with a single state of reality.
Lewis, Peter G; Jennings, David; Barrett, Jonathan; Rudolph, Terry
2012-10-12
Perhaps the quantum state represents information about reality, and not reality directly. Wave function collapse is then possibly no more mysterious than a Bayesian update of a probability distribution given new data. We consider models for quantum systems with measurement outcomes determined by an underlying physical state of the system but where several quantum states are consistent with a single underlying state-i.e., probability distributions for distinct quantum states overlap. Significantly, we demonstrate by example that additional assumptions are always necessary to rule out such a model. PMID:23102280
Interference with a quantum dot single-photon source and a laser at telecom wavelength
Felle, M.; Huwer, J. Stevenson, R. M.; Skiba-Szymanska, J.; Ward, M. B.; Shields, A. J.; Farrer, I.; Ritchie, D. A.; Penty, R. V.
2015-09-28
The interference of photons emitted by dissimilar sources is an essential requirement for a wide range of photonic quantum information applications. Many of these applications are in quantum communications and need to operate at standard telecommunication wavelengths to minimize the impact of photon losses and be compatible with existing infrastructure. Here, we demonstrate for the first time the quantum interference of telecom-wavelength photons from an InAs/GaAs quantum dot single-photon source and a laser; an important step towards such applications. The results are in good agreement with a theoretical model, indicating a high degree of indistinguishability for the interfering photons.
Injection of a single electron from static to moving quantum dots
NASA Astrophysics Data System (ADS)
Bertrand, Benoit; Hermelin, Sylvain; Mortemousque, Pierre-André; Takada, Shintaro; Yamamoto, Michihisa; Tarucha, Seigo; Ludwig, Arne; Wieck, Andreas D.; Bäuerle, Christopher; Meunier, Tristan
2016-05-01
We study the injection mechanism of a single electron from a static quantum dot into a moving quantum dot. The moving quantum dots are created with surface acoustic waves (SAWs) in a long depleted channel. We demonstrate that the injection process is characterized by an activation law with a threshold that depends on the SAW amplitude and on the dot-channel potential gradient. By sufficiently increasing the SAW modulation amplitude, we can reach a regime where the transfer has unity probability and is potentially adiabatic. This study points to the relevant regime to use moving dots in quantum information protocols.
Heralded Storage of a Photonic Quantum Bit in a Single Atom.
Kalb, Norbert; Reiserer, Andreas; Ritter, Stephan; Rempe, Gerhard
2015-06-01
Combining techniques of cavity quantum electrodynamics, quantum measurement, and quantum feedback, we have realized the heralded transfer of a polarization qubit from a photon onto a single atom with 39% efficiency and 86% fidelity. The reverse process, namely, qubit transfer from the atom onto a given photon, is demonstrated with 88% fidelity and an estimated efficiency of up to 69%. In contrast to previous work based on two-photon interference, our scheme is robust against photon arrival-time jitter and achieves much higher efficiencies. Thus, it constitutes a key step toward the implementation of a long-distance quantum network. PMID:26196608
Lippen, T. van; Noetzel, R.; Hamhuis, G.J.; Wolter, J.H.
2005-02-15
An ordered lattice of lateral InAs quantum dot (QD) molecules is created by self-organized anisotropic strain engineering of an (In,Ga)As/GaAs superlattice (SL) template on GaAs(311)B by molecular-beam epitaxy, constituting a Turing pattern in solid state. The SL template and InAs QD growth conditions, such as the number of SL periods, growth temperatures, amount and composition of deposited (In,Ga)As, and insertion of Al-containing layers, are studied in detail for an optimized QD ordering within and among the InAs QD molecules on the SL template nodes, which is evaluated by atomic force microscopy. The average number of InAs QDs within the molecules is controlled by the thickness of the upper GaAs separation layer on the SL template and the (In,Ga)As growth temperature in the SL. The strain-correlated growth in SL template formation and QD ordering is directly confirmed by high-resolution x-ray diffraction. Ordered arrays of single InAs QDs on the SL template nodes are realized for elevated SL template and InAs QD growth temperatures together with the insertion of a second InAs QD layer. The InAs QD molecules exhibit strong photoluminescence (PL) emission up to room temperature. Temperature-dependent PL measurements exhibit an unusual behavior of the full width at half maximum, indicating carrier redistribution solely within the QD molecules.
Two-message quantum-Arthur-Merlin game with single-qubit measurements
NASA Astrophysics Data System (ADS)
Morimae, Tomoyuki
2016-06-01
We show that the class quantum-Arthur-Merlin (QAM) does not change even if the verifier's ability is restricted to only single-qubit measurements. To show the result, we use the idea of measurement-based quantum computing: the verifier, who can do only single-qubit measurements, can test the graph state sent from the prover and use it for his measurement-based quantum computing. Inspired by this construction, we also introduce a problem which we call stabilizer state optimization, and show that it is QMA-complete.
Quantum Router for Single Photons Carrying Spin and Orbital Angular Momentum
NASA Astrophysics Data System (ADS)
Chen, Yuanyuan; Jiang, Dong; Xie, Ling; Chen, Lijun
2016-06-01
Quantum router is an essential element in the quantum network. Here, we present a fully quantum router based on interaction free measurement and quantum dots. The signal photonic qubit can be routed to different output ports according to one control electronic qubit. Besides, our scheme is an interferometric method capable of routing single photons carrying either spin angular momentum (SAM) or orbital angular momentum (OAM), or simultaneously carrying SAM and OAM. Then we describe a cascaded multi-level quantum router to construct a one-to-many quantum router. Subsequently we analyze the success probability by using a tunable controlled phase gate. The implementation issues are also discussed to show that this scheme is feasible.
Quantum Router for Single Photons Carrying Spin and Orbital Angular Momentum.
Chen, Yuanyuan; Jiang, Dong; Xie, Ling; Chen, Lijun
2016-01-01
Quantum router is an essential element in the quantum network. Here, we present a fully quantum router based on interaction free measurement and quantum dots. The signal photonic qubit can be routed to different output ports according to one control electronic qubit. Besides, our scheme is an interferometric method capable of routing single photons carrying either spin angular momentum (SAM) or orbital angular momentum (OAM), or simultaneously carrying SAM and OAM. Then we describe a cascaded multi-level quantum router to construct a one-to-many quantum router. Subsequently we analyze the success probability by using a tunable controlled phase gate. The implementation issues are also discussed to show that this scheme is feasible. PMID:27256772
Quantum Router for Single Photons Carrying Spin and Orbital Angular Momentum
Chen, Yuanyuan; Jiang, Dong; Xie, Ling; Chen, Lijun
2016-01-01
Quantum router is an essential element in the quantum network. Here, we present a fully quantum router based on interaction free measurement and quantum dots. The signal photonic qubit can be routed to different output ports according to one control electronic qubit. Besides, our scheme is an interferometric method capable of routing single photons carrying either spin angular momentum (SAM) or orbital angular momentum (OAM), or simultaneously carrying SAM and OAM. Then we describe a cascaded multi-level quantum router to construct a one-to-many quantum router. Subsequently we analyze the success probability by using a tunable controlled phase gate. The implementation issues are also discussed to show that this scheme is feasible. PMID:27256772
Toward Real-time quantum imaging with a single pixel camera
Lawrie, Benjamin J; Pooser, Raphael C
2013-01-01
We present a workbench for the study of real-time quantum imaging by measuring the frame-by-frame quantum noise reduction of multi-spatial-mode twin beams generated by four wave mixing in Rb vapor. Exploiting the multiple spatial modes of this squeezed light source, we utilize spatial light modulators to selectively transmit macropixels of quantum correlated modes from each of the twin beams to a high quantum efficiency balanced detector. In low-light-level imaging applications, the ability to measure the quantum correlations between individual spatial modes and macropixels of spatial modes with a single pixel camera will facilitate compressive quantum imaging with sensitivity below the photon shot noise limit.
Quantum-state purity of heralded single photons produced from frequency-anticorrelated biphotons
NASA Astrophysics Data System (ADS)
Du, Shengwang
2015-10-01
We analyze the quantum-state purity of heralded single photons produced from frequency-anticorrelated biphotons. We find that the quantum-state purity in the time-frequency domain depends strongly on the response time uncertainty of the trigger-photon detector that heralds the generation of its paired photon. If the trigger response time is much shorter than the two-photon coherence time, the time-frequency quantum-state purity of heralded single photons approaches unity and the heralded single photon is in a nearly pure state. If the trigger response time is much longer than the two-photon coherence time, the heralded photon is then projected onto a mixed state. Making use of the time-frequency entanglement, heralded single photons with a well-defined temporal wave function or a frequency superposition state can be produced and engineered. This time-frequency entanglement allows for shaping heralded single photons through nonlocal spectral modulation.
Single photons on-demand from light-hole excitons in strain-engineered quantum dots.
Zhang, Jiaxiang; Huo, Yongheng; Rastelli, Armando; Zopf, Michael; Höfer, Bianca; Chen, Yan; Ding, Fei; Schmidt, Oliver G
2015-01-14
We demonstrate for the first time on-demand and wavelength-tunable single-photon emission from light-hole (LH) excitons in strain engineered GaAs quantum dots (QDs). The LH photon emission from tensile-strained GaAs QDs is systematically investigated with polarization-resolved, power-dependent photoluminescence spectroscopy, and photon-correlation measurements. By integrating QD-containing nanomembranes onto a piezo-actuator and driving single QDs with picosecond laser pulses, we achieve triggered and wavelength-tunable LH single-photon emission. Fourier transform spectroscopy is also performed, from which the coherence time of the LH single-photon emission is studied. We envision that this new type of LH exciton-based single-photon source (SPS) can be applied to realize an all-semiconductor based quantum interface in distributed quantum networks [Phys. Rev. Lett. 2008, 100, 096602]. PMID:25471544
Observation of Dressed Excitonic States in a Single Quantum Dot
NASA Astrophysics Data System (ADS)
Jundt, Gregor; Robledo, Lucio; Högele, Alexander; Fält, Stefan; Imamoǧlu, Atac
2008-05-01
We report the observation of dressed states of a quantum dot. The optically excited exciton and biexciton states of the quantum dot are coupled by a strong laser field and the resulting spectral signatures are measured using differential transmission of a probe field. We demonstrate that the anisotropic electron-hole exchange interaction induced splitting between the x- and y-polarized excitonic states can be completely erased by using the ac-Stark effect induced by the coupling field, without causing any appreciable broadening of the spectral lines. We also show that by varying the polarization and strength of a resonant coupling field, we can effectively change the polarization axis of the quantum dot.
Overcoming lossy channel bounds using a single quantum repeater node
NASA Astrophysics Data System (ADS)
Luong, D.; Jiang, L.; Kim, J.; Lütkenhaus, N.
2016-04-01
We propose a scheme for performing quantum key distribution (QKD) which has the potential to beat schemes based on the direct transmission of photons between the communicating parties. In our proposal, the communicating parties exchange photons with two quantum memories placed between them. This is a very simple quantum repeater scheme and can be implemented with currently available technology. Ideally, its secret key rate scales as the square root of the transmittivity of the optical channel, which is superior to QKD schemes based on direct transmission because key rates for the latter scale at best linearly with transmittivity. Taking into account various imperfections in each component of our setup, we present parameter regimes in which our protocol outperforms protocols based on direct transmission.
Nonlinear waves and coherent structures in the quantum single-wave model
Tzenov, Stephan I.; Marinov, Kiril B.
2011-10-15
Starting from the von Neumann-Maxwell equations for the Wigner quasi-probability distribution and for the self-consistent electric field, the quantum analog of the classical single-wave model has been derived. The linear stability of the quantum single-wave model has been studied, and periodic in time patterns have been found both analytically and numerically. In addition, some features of quantum chaos have been detected in the unstable region in parameter space. Further, a class of standing-wave solutions of the quantum single-wave model has also been found, which have been observed to behave as stable solitary-wave structures. The analytical results have been finally compared to the exact system dynamics obtained by solving the corresponding equations in Schrodinger representation numerically.
Theoertical investigation of quantum waveform shaping for single photon emitters.
Pedrotti, Leno M; Agha, Imad
2016-07-25
We investigate a new technique for quantum-compatible waveform shaping that extends the time lens method, and relies only on phase operations. Under realistic experimental conditions, we show that it is possible to both temporally compress and shape optical waveforms in the nanosecond to tens of picoseconds range, which is generally difficult to achieve using standard dispersive pulse-shaping techniques. PMID:27464122
Making Ternary Quantum Dots From Single-Source Precursors
NASA Technical Reports Server (NTRS)
Bailey, Sheila; Banger, Kulbinder; Castro, Stephanie; Hepp, Aloysius
2007-01-01
A process has been devised for making ternary (specifically, CuInS2) nanocrystals for use as quantum dots (QDs) in a contemplated next generation of high-efficiency solar photovoltaic cells. The process parameters can be chosen to tailor the sizes (and, thus, the absorption and emission spectra) of the QDs.
Single-hidden-layer feed-forward quantum neural network based on Grover learning.
Liu, Cheng-Yi; Chen, Chein; Chang, Ching-Ter; Shih, Lun-Min
2013-09-01
In this paper, a novel single-hidden-layer feed-forward quantum neural network model is proposed based on some concepts and principles in the quantum theory. By combining the quantum mechanism with the feed-forward neural network, we defined quantum hidden neurons and connected quantum weights, and used them as the fundamental information processing unit in a single-hidden-layer feed-forward neural network. The quantum neurons make a wide range of nonlinear functions serve as the activation functions in the hidden layer of the network, and the Grover searching algorithm outstands the optimal parameter setting iteratively and thus makes very efficient neural network learning possible. The quantum neuron and weights, along with a Grover searching algorithm based learning, result in a novel and efficient neural network characteristic of reduced network, high efficient training and prospect application in future. Some simulations are taken to investigate the performance of the proposed quantum network and the result show that it can achieve accurate learning. PMID:23545155
An integrated quantum repeater at telecom wavelength with single atoms in optical fiber cavities
NASA Astrophysics Data System (ADS)
Uphoff, Manuel; Brekenfeld, Manuel; Rempe, Gerhard; Ritter, Stephan
2016-03-01
Quantum repeaters promise to enable quantum networks over global distances by circumventing the exponential decrease in success probability inherent in direct photon transmission. We propose a realistic, functionally integrated quantum-repeater implementation based on single atoms in optical cavities. Entanglement is directly generated between the single-atom quantum memory and a photon at telecom wavelength. The latter is collected with high efficiency and adjustable temporal and spectral properties into a spatially well-defined cavity mode. It is heralded by a near-infrared photon emitted from a second, orthogonal cavity. Entanglement between two remote quantum memories can be generated via an optical Bell-state measurement, while we propose entanglement swapping based on a highly efficient, cavity-assisted atom-atom gate. Our quantum-repeater scheme eliminates any requirement for wavelength conversion such that only a single system is needed at each node. We investigate a particular implementation with rubidium and realistic parameters for Fabry-Perot cavities based on hbox {CO}_2 laser-machined optical fibers. We show that the scheme enables the implementation of a rather simple quantum repeater that outperforms direct entanglement generation over large distances and does not require any improvements in technology beyond the state of the art.
A quantum phase switch between a single solid-state spin and a photon.
Sun, Shuo; Kim, Hyochul; Solomon, Glenn S; Waks, Edo
2016-06-01
Interactions between single spins and photons are essential for quantum networks and distributed quantum computation. Achieving spin-photon interactions in a solid-state device could enable compact chip-integrated quantum circuits operating at gigahertz bandwidths. Many theoretical works have suggested using spins embedded in nanophotonic structures to attain this high-speed interface. These proposals implement a quantum switch where the spin flips the state of the photon and a photon flips the spin state. However, such a switch has not yet been realized using a solid-state spin system. Here, we report an experimental realization of a spin-photon quantum switch using a single solid-state spin embedded in a nanophotonic cavity. We show that the spin state strongly modulates the polarization of a reflected photon, and a single reflected photon coherently rotates the spin state. These strong spin-photon interactions open up a promising direction for solid-state implementations of high-speed quantum networks and on-chip quantum information processors using nanophotonic devices. PMID:26854569
A quantum phase switch between a single solid-state spin and a photon
NASA Astrophysics Data System (ADS)
Sun, Shuo; Kim, Hyochul; Solomon, Glenn S.; Waks, Edo
2016-06-01
Interactions between single spins and photons are essential for quantum networks and distributed quantum computation. Achieving spin–photon interactions in a solid-state device could enable compact chip-integrated quantum circuits operating at gigahertz bandwidths. Many theoretical works have suggested using spins embedded in nanophotonic structures to attain this high-speed interface. These proposals implement a quantum switch where the spin flips the state of the photon and a photon flips the spin state. However, such a switch has not yet been realized using a solid-state spin system. Here, we report an experimental realization of a spin–photon quantum switch using a single solid-state spin embedded in a nanophotonic cavity. We show that the spin state strongly modulates the polarization of a reflected photon, and a single reflected photon coherently rotates the spin state. These strong spin–photon interactions open up a promising direction for solid-state implementations of high-speed quantum networks and on-chip quantum information processors using nanophotonic devices.
Red, green, and blue lasing enabled by single-exciton gain in colloidal quantum dot films
Nurmikko, Arto V.; Dang, Cuong
2016-06-21
The methods and materials described herein contemplate the use films of colloidal quantum dots as a gain medium in a vertical-cavity surface-emitting laser. The present disclosure demonstrates a laser with single-exciton gain in the red, green, and blue wavelengths. Leveraging this nanocomposite gain, the results realize a significant step toward full-color single-material lasers.
Photoluminescence intermittency from single quantum dots to organic molecules: emerging themes.
Riley, Erin A; Hess, Chelsea M; Reid, Philip J
2012-01-01
Recent experimental and theoretical studies of photoluminescence intermittency (PI) or "blinking" exhibited by single core/shell quantum dots and single organic luminophores are reviewed. For quantum dots, a discussion of early models describing the origin of PI in these materials and recent challenges to these models are presented. For organic luminophores the role of electron transfer, proton transfer and other photophysical processes in PI are discussed. Finally, new experimental and data analysis methods are outlined that promise to be instrumental in future discoveries regarding the origin(s) of PI exhibited by single emitters. PMID:23202909
Elliptical quantum dots as on-demand single photons sources with deterministic polarization states
Teng, Chu-Hsiang; Demory, Brandon; Ku, Pei-Cheng; Zhang, Lei; Hill, Tyler A.; Deng, Hui
2015-11-09
In quantum information, control of the single photon's polarization is essential. Here, we demonstrate single photon generation in a pre-programmed and deterministic polarization state, on a chip-scale platform, utilizing site-controlled elliptical quantum dots (QDs) synthesized by a top-down approach. The polarization from the QD emission is found to be linear with a high degree of linear polarization and parallel to the long axis of the ellipse. Single photon emission with orthogonal polarizations is achieved, and the dependence of the degree of linear polarization on the QD geometry is analyzed.
Photoluminescence Intermittency from Single Quantum Dots to Organic Molecules: Emerging Themes
Riley, Erin A.; Hess, Chelsea M.; Reid, Philip J.
2012-01-01
Recent experimental and theoretical studies of photoluminescence intermittency (PI) or “blinking” exhibited by single core/shell quantum dots and single organic luminophores are reviewed. For quantum dots, a discussion of early models describing the origin of PI in these materials and recent challenges to these models are presented. For organic luminophores the role of electron transfer, proton transfer and other photophysical processes in PI are discussed. Finally, new experimental and data analysis methods are outlined that promise to be instrumental in future discoveries regarding the origin(s) of PI exhibited by single emitters. PMID:23202909
Elliptical quantum dots as on-demand single photons sources with deterministic polarization states
NASA Astrophysics Data System (ADS)
Teng, Chu-Hsiang; Zhang, Lei; Hill, Tyler A.; Demory, Brandon; Deng, Hui; Ku, Pei-Cheng
2015-11-01
In quantum information, control of the single photon's polarization is essential. Here, we demonstrate single photon generation in a pre-programmed and deterministic polarization state, on a chip-scale platform, utilizing site-controlled elliptical quantum dots (QDs) synthesized by a top-down approach. The polarization from the QD emission is found to be linear with a high degree of linear polarization and parallel to the long axis of the ellipse. Single photon emission with orthogonal polarizations is achieved, and the dependence of the degree of linear polarization on the QD geometry is analyzed.
Distinct Quantum States Can Be Compatible with a Single State of Reality
NASA Astrophysics Data System (ADS)
Lewis, Peter; Jennings, David; Barrett, Jonathan; Rudolph, Terry
2013-03-01
Perhaps the quantum state represents information available to some agent or experimenter about reality, and not reality directly. This view is attractive because if quantum states represent only information, then wave function collapse is possibly no more mysterious than a Bayesian update of a probability distribution given new data. Several other ``puzzling'' features of quantum theory also follow naturally given this view. In order to explore this idea rigorously, we consider models for quantum systems with probabilities for measurement outcomes determined by some underlying physical state of the system, where the underlying state is not necessarily described by quantum theory. In our model, quantum states correspond to probability distributions over the underlying states so that the Born rule is recovered. More specifically, we consider models for quantum systems where several quantum states are consistent with a single underlying state-i.e., probability distributions for distinct quantum states overlap. Recent work shows that such a model is impossible (e.g. the PBR theorem (Nat. Phys. 8, p.474)). Significantly, our example demonstrates that non-trivial assumptions (beyond those required for a well-defined realistic model) are necessary for the PBR theorem and those like it. This work was supported by the Engineering and Physical Sciences Research Council, Leverhulme Foundation and The Royal Commission for the Exhibition of 1851
Single-photon emission from cubic GaN quantum dots
Kako, Satoshi; Holmes, Mark; Sergent, Sylvain; Bürger, Matthias; As, Donat J.; Arakawa, Yasuhiko
2014-01-06
We report the demonstration of single-photon emission from cubic GaN/AlN quantum dots grown by molecular beam epitaxy. We have observed spectrally clean and isolated emission peaks from these quantum dots. Clear single-photon emission was detected by analyzing one such peak at 4 K. The estimated g{sup (2)}[0] value is 0.25, which becomes 0.05 when corrected for background and detector dark counts. We have also observed the single-photon nature of the emission up to 100 K (g{sup (2)}[0] = 0.47). These results indicate that cubic GaN quantum dots are possible candidates for high-temperature operating UV single-photon sources with the possibility of integration into photonic nanostructures.
Detection of single quantum dots in model organisms with sheet illumination microscopy
Friedrich, Mike; Nozadze, Revaz; Gan, Qiang; Zelman-Femiak, Monika; Ermolayev, Vladimir; Wagner, Toni U.; Harms, Gregory S.
2009-12-18
Single-molecule detection and tracking is important for observing biomolecule interactions in the microenvironment. Here we report selective plane illumination microscopy (SPIM) with single-molecule detection in living organisms, which enables fast imaging and single-molecule tracking and optical penetration beyond 300 {mu}m. We detected single nanocrystals in Drosophila larvae and zebrafish embryo. We also report our first tracking of single quantum dots during zebrafish development, which displays a transition from flow to confined motion prior to the blastula stage. The new SPIM setup represents a new technique, which enables fast single-molecule imaging and tracking in living systems.
A quantum gate between a flying optical photon and a single trapped atom.
Reiserer, Andreas; Kalb, Norbert; Rempe, Gerhard; Ritter, Stephan
2014-04-10
The steady increase in control over individual quantum systems supports the promotion of a quantum technology that could provide functionalities beyond those of any classical device. Two particularly promising applications have been explored during the past decade: photon-based quantum communication, which guarantees unbreakable encryption but which still has to be scaled to high rates over large distances, and quantum computation, which will fundamentally enhance computability if it can be scaled to a large number of quantum bits (qubits). It was realized early on that a hybrid system of light qubits and matter qubits could solve the scalability problem of each field--that of communication by use of quantum repeaters, and that of computation by use of an optical interconnect between smaller quantum processors. To this end, the development of a robust two-qubit gate that allows the linking of distant computational nodes is "a pressing challenge". Here we demonstrate such a quantum gate between the spin state of a single trapped atom and the polarization state of an optical photon contained in a faint laser pulse. The gate mechanism presented is deterministic and robust, and is expected to be applicable to almost any matter qubit. It is based on reflection of the photonic qubit from a cavity that provides strong light-matter coupling. To demonstrate its versatility, we use the quantum gate to create atom-photon, atom-photon-photon and photon-photon entangled states from separable input states. We expect our experiment to enable various applications, including the generation of atomic and photonic cluster states and Schrödinger-cat states, deterministic photonic Bell-state measurements, scalable quantum computation and quantum communication using a redundant quantum parity code. PMID:24717512
Realizing quantum advantage without entanglement in single-photon states
NASA Astrophysics Data System (ADS)
Maldonado-Trapp, Alejandra; Solano, Pablo; Hu, Anzi; Clark, Charles W.
Correlations allow us to measure, and quantitatively study, the properties of physical systems, their evolution and their interactions. Quantum discord expresses quantum correlations beyond those associated with entanglement. However, discord has not yet been adopted as a standard subject of study by the experimental community. Here we propose a feasible optical setup to generate symmetric two-qubit X-states with controllable coherences, where the two qubits correspond to the spin and path of a photon. With these states we show how a classical random variable K can be encoded by Alice and decoded by Bob. Using our previous results we study the correlations between the spin and path qubits and its relation with the information about K that can be decoded by Bob using local measurements with or without two-qubit gate operations. Discord is the mutual information contained in the coherences of the system, and it is possible to exploit it for quantum advantage even in the absence of entanglement.
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.
Self-aligned deterministic coupling of single quantum emitter to nanofocused plasmonic modes
Gong, Su-Hyun; Kim, Je-Hyung; Ko, Young-Ho; Rodriguez, Christophe; Shin, Jonghwa; Lee, Yong-Hee; Dang, Le Si; Zhang, Xiang; Cho, Yong-Hoon
2015-01-01
The quantum plasmonics field has emerged and been growing increasingly, including study of single emitter–light coupling using plasmonic system and scalable quantum plasmonic circuit. This offers opportunity for the quantum control of light with compact device footprint. However, coupling of a single emitter to highly localized plasmonic mode with nanoscale precision remains an important challenge. Today, the spatial overlap between metallic structure and single emitter mostly relies either on chance or on advanced nanopositioning control. Here, we demonstrate deterministic coupling between three-dimensionally nanofocused plasmonic modes and single quantum dots (QDs) without any positioning for single QDs. By depositing a thin silver layer on a site-controlled pyramid QD wafer, three-dimensional plasmonic nanofocusing on each QD at the pyramid apex is geometrically achieved through the silver-coated pyramid facets. Enhancement of the QD spontaneous emission rate as high as 22 ± 16 is measured for all processed QDs emitting over ∼150-meV spectral range. This approach could apply to high fabrication yield on-chip devices for wide application fields, e.g., high-efficiency light-emitting devices and quantum information processing. PMID:25870303
NASA Astrophysics Data System (ADS)
Gao, Qing; Dong, Daoyi; Petersen, Ian R.; Rabitz, Herschel
2016-06-01
The purpose of this paper is to solve the fault tolerant filtering and fault detection problem for a class of open quantum systems driven by a continuous-mode bosonic input field in single photon states when the systems are subject to stochastic faults. Optimal estimates of both the system observables and the fault process are simultaneously calculated and characterized by a set of coupled recursive quantum stochastic differential equations.
Nonlocal biphoton generation in a Werner state from a single semiconductor quantum dot
NASA Astrophysics Data System (ADS)
Kumano, H.; Nakajima, H.; Kuroda, T.; Mano, T.; Sakoda, K.; Suemune, I.
2015-05-01
We demonstrate the generation of a Werner-like state from a single semiconductor quantum dot. The tomographic analysis with temporal gating brings us to a systematic understanding of the relation between the time evolution of quantum correlation and a set of parameters characterizing the exciton states, including fine-structure splitting and cross-dephasing time. The Werner state relates the Bell's parameter in the Clauser, Horne, Shimony, and Holt inequality with a fidelity, which facilitates the evaluation of nonlocality.
Photoluminescence Spectroscopy of CdZnTe/CdTe Single Strained Quantum Wells
NASA Astrophysics Data System (ADS)
Reno, J. L.; Jones, E. D.
1991-12-01
We have grown strained Cd1-xZnxTe/CdTe single strained quantum wells by molecular beam epitaxy. The Zn concentration was varied from 10 to 60% and the well widths were systematically increased until the critical thickness was exceeded. Low-temperature (liquid helium) photoluminescence spectroscopy was used to characterize the films. The energy of the quantum well luminescence is consistent with a simple square well model when strain is included. The critical layer thickness for the CdTe quantum wells was found to be in agreement with the model of Matthews and Blakeslee.
Channel analysis for single photon underwater free space quantum key distribution.
Shi, Peng; Zhao, Shi-Cheng; Gu, Yong-Jian; Li, Wen-Dong
2015-03-01
We investigate the optical absorption and scattering properties of underwater media pertinent to our underwater free space quantum key distribution (QKD) channel model. With the vector radiative transfer theory and Monte Carlo method, we obtain the attenuation of photons, the fidelity of the scattered photons, the quantum bit error rate, and the sifted key generation rate of underwater quantum communication. It can be observed from our simulations that the most secure single photon underwater free space QKD is feasible in the clearest ocean water. PMID:26366645
Applications of single-qubit rotations in quantum public-key cryptography
NASA Astrophysics Data System (ADS)
Nikolopoulos, Georgios M.
2008-03-01
We discuss cryptographic applications of single-qubit rotations from the perspective of trapdoor one-way functions and public-key encryption. In particular, we present an asymmetric cryptosystem whose security relies on fundamental principles of quantum physics. A quantum public key is used for the encryption of messages while decryption is possible by means of a classical private key only. The trapdoor one-way function underlying the proposed cryptosystem maps integer numbers to quantum states of a qubit and its inversion can be infeasible by virtue of the Holevo’s theorem.
Clustered quantum dots in single GaN islands formed at threading dislocations
NASA Astrophysics Data System (ADS)
Schmidt, Gordon; Veit, Peter; Berger, Christoph; Bertram, Frank; Dadgar, Armin; Strittmatter, André; Christen, Jürgen
2016-05-01
We give direct evidence of distinct quantum dot states clustered but also spatially separated in single GaN islands. Resulting from GaN layer growth on top of AlN, the islands are predominantly formed in close vicinity to threading dislocation bundles. Detailed analysis of the inner optical and structural properties, performed by nanoscale cathodoluminescence, reveals various sharp quantum dot emission lines from different regions in an otherwise continuous island. Thickness fluctuations found within these islands are made responsible for the clustering of quantum dot states.
NASA Astrophysics Data System (ADS)
Hofmann, Holger F.
2014-04-01
Recent results obtained in quantum measurements indicate that the fundamental relations between three physical properties of a system can be represented by complex conditional probabilities. Here, it is shown that these relations provide a fully deterministic and universally valid framework on which all of quantum mechanics can be based. Specifically, quantum mechanics can be derived by combining the rules of Bayesian probability theory with only a single additional law that explains the phases of complex probabilities. This law, which I introduce here as the law of quantum ergodicity, is based on the observation that the reality of physical properties cannot be separated from the dynamics by which they emerge in measurement interactions. The complex phases are an expression of this inseparability and represent the dynamical structure of transformations between the different properties. In its quantitative form, the law of quantum ergodicity describes a fundamental relation between the ergodic probabilities obtained by dynamical averaging and the deterministic relations between three properties expressed by the complex conditional probabilities. The complete formalism of quantum mechanics can be derived from this one relation, without any axiomatic mathematical assumptions about state vectors or superpositions. It is therefore possible to explain all quantum phenomena as the consequence of a single fundamental law of physics.
Measuring the quantum state of a single system with minimum state disturbance
NASA Astrophysics Data System (ADS)
Schlosshauer, Maximilian
2016-01-01
Conventionally, unknown quantum states are characterized using quantum-state tomography based on strong or weak measurements carried out on an ensemble of identically prepared systems. By contrast, the use of protective measurements offers the possibility of determining quantum states from a series of weak, long measurements performed on a single system. Because the fidelity of a protectively measured quantum state is determined by the amount of state disturbance incurred during each protective measurement, it is crucial that the initial quantum state of the system is disturbed as little as possible. Here we show how to systematically minimize the state disturbance in the course of a protective measurement, thus enabling the maximization of the fidelity of the quantum-state measurement. Our approach is based on a careful tuning of the time dependence of the measurement interaction and is shown to be dramatically more effective in reducing the state disturbance than the previously considered strategy of weakening the measurement strength and increasing the measurement time. We describe a method for designing the measurement interaction such that the state disturbance exhibits polynomial decay to arbitrary order in the inverse measurement time 1 /T . We also show how one can achieve even faster, subexponential decay, and we find that it represents the smallest possible state disturbance in a protective measurement. In this way, our results show how to optimally measure the state of a single quantum system using protective measurements.
Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping.
Rossi, Alessandro; Tanttu, Tuomo; Hudson, Fay E; Sun, Yuxin; Möttönen, Mikko; Dzurak, Andrew S
2015-01-01
As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by quantum mechanical effects such as tunneling through single dopants, scattering via interface defects, and discrete trap charge states. However, progress in silicon technology has shown that these phenomena can be harnessed and exploited for a new class of quantum-based electronics. Among others, multi-layer-gated silicon metal-oxide-semiconductor (MOS) technology can be used to control single charge or spin confined in electrostatically-defined quantum dots (QD). These QD-based devices are an excellent platform for quantum computing applications and, recently, it has been demonstrated that they can also be used as single-electron pumps, which are accurate sources of quantized current for metrological purposes. Here, we discuss in detail the fabrication protocol for silicon MOS QDs which is relevant to both quantum computing and quantum metrology applications. Moreover, we describe characterization methods to test the integrity of the devices after fabrication. Finally, we give a brief description of the measurement set-up used for charge pumping experiments and show representative results of electric current quantization. PMID:26067215
Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping
Rossi, Alessandro; Tanttu, Tuomo; Hudson, Fay E.; Sun, Yuxin; Möttönen, Mikko; Dzurak, Andrew S.
2015-01-01
As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by quantum mechanical effects such as tunneling through single dopants, scattering via interface defects, and discrete trap charge states. However, progress in silicon technology has shown that these phenomena can be harnessed and exploited for a new class of quantum-based electronics. Among others, multi-layer-gated silicon metal-oxide-semiconductor (MOS) technology can be used to control single charge or spin confined in electrostatically-defined quantum dots (QD). These QD-based devices are an excellent platform for quantum computing applications and, recently, it has been demonstrated that they can also be used as single-electron pumps, which are accurate sources of quantized current for metrological purposes. Here, we discuss in detail the fabrication protocol for silicon MOS QDs which is relevant to both quantum computing and quantum metrology applications. Moreover, we describe characterization methods to test the integrity of the devices after fabrication. Finally, we give a brief description of the measurement set-up used for charge pumping experiments and show representative results of electric current quantization. PMID:26067215
NASA Astrophysics Data System (ADS)
Weng, Qianchun; An, Zhenghua; Zhang, Bo; Chen, Pingping; Chen, Xiaoshuang; Zhu, Ziqiang; Lu, Wei
2015-03-01
Low-noise single-photon detectors that can resolve photon numbers are used to monitor the operation of quantum gates in linear-optical quantum computation. Exactly 0, 1 or 2 photons registered in a detector should be distinguished especially in long-distance quantum communication and quantum computation. Here we demonstrate a photon-number-resolving detector based on quantum dot coupled resonant tunneling diodes (QD-cRTD). Individual quantum-dots (QDs) coupled closely with adjacent quantum well (QW) of resonant tunneling diode operate as photon-gated switches- which turn on (off) the RTD tunneling current when they trap photon-generated holes (recombine with injected electrons). Proposed electron-injecting operation fills electrons into coupled QDs which turn ``photon-switches'' to ``OFF'' state and make the detector ready for multiple-photons detection. With proper decision regions defined, 1-photon and 2-photon states are resolved in 4.2 K with excellent propabilities of accuracy of 90% and 98% respectively. Further, by identifying step-like photon responses, the photon-number-resolving capability is sustained to 77 K, making the detector a promising candidate for advanced quantum information applications where photon-number-states should be accurately distinguished.
Weng, Qianchun; An, Zhenghua; Zhang, Bo; Chen, Pingping; Chen, Xiaoshuang; Zhu, Ziqiang; Lu, Wei
2015-01-01
Low-noise single-photon detectors that can resolve photon numbers are used to monitor the operation of quantum gates in linear-optical quantum computation. Exactly 0, 1 or 2 photons registered in a detector should be distinguished especially in long-distance quantum communication and quantum computation. Here we demonstrate a photon-number-resolving detector based on quantum dot coupled resonant tunneling diodes (QD-cRTD). Individual quantum-dots (QDs) coupled closely with adjacent quantum well (QW) of resonant tunneling diode operate as photon-gated switches- which turn on (off) the RTD tunneling current when they trap photon-generated holes (recombine with injected electrons). Proposed electron-injecting operation fills electrons into coupled QDs which turn “photon-switches” to “OFF” state and make the detector ready for multiple-photons detection. With proper decision regions defined, 1-photon and 2-photon states are resolved in 4.2 K with excellent propabilities of accuracy of 90% and 98% respectively. Further, by identifying step-like photon responses, the photon-number-resolving capability is sustained to 77 K, making the detector a promising candidate for advanced quantum information applications where photon-number-states should be accurately distinguished. PMID:25797442
Weng, Qianchun; An, Zhenghua; Zhang, Bo; Chen, Pingping; Chen, Xiaoshuang; Zhu, Ziqiang; Lu, Wei
2015-01-01
Low-noise single-photon detectors that can resolve photon numbers are used to monitor the operation of quantum gates in linear-optical quantum computation. Exactly 0, 1 or 2 photons registered in a detector should be distinguished especially in long-distance quantum communication and quantum computation. Here we demonstrate a photon-number-resolving detector based on quantum dot coupled resonant tunneling diodes (QD-cRTD). Individual quantum-dots (QDs) coupled closely with adjacent quantum well (QW) of resonant tunneling diode operate as photon-gated switches- which turn on (off) the RTD tunneling current when they trap photon-generated holes (recombine with injected electrons). Proposed electron-injecting operation fills electrons into coupled QDs which turn "photon-switches" to "OFF" state and make the detector ready for multiple-photons detection. With proper decision regions defined, 1-photon and 2-photon states are resolved in 4.2 K with excellent propabilities of accuracy of 90% and 98% respectively. Further, by identifying step-like photon responses, the photon-number-resolving capability is sustained to 77 K, making the detector a promising candidate for advanced quantum information applications where photon-number-states should be accurately distinguished. PMID:25797442
Plasmonic Effect on Exciton and Multiexciton Emission of Single Quantum Dots.
Dey, Swayandipta; Zhao, Jing
2016-08-01
Quantum dots are nanoscale quantum emitters with high quantum yield and size-dependent emission wavelength, holding promises in many optical and electronic applications. When quantum dots are situated close to noble metal nanoparticles, their emitting behavior can be conveniently tuned because of the interaction between the excitons of the quantum dots and the plasmons of the metal nanoparticles. This interaction at the single quantum dot level gives rise to reduced or suppressed photoluminescence blinking and enhanced multiexciton emission, which is difficult to achieve in isolated quantum dots. However, the mechanism of how plasmonic structures cause the changes in the quantum dot emission remains unclear. Because of the complexity of the system, the interfaces between metal, semiconductor, and ligands must be considered, in addition to factors such as geometry, interparticle distance, and spectral overlap. The challenges in the design and fabrication of the hybrid nanostructures as well as in understanding the exciton-plasmon coupling mechanism can be overcome by a cooperative effort in synthesis, optical spectroscopy, and theoretical modeling. PMID:27411778
Simplified quantum bit commitment using single photon nonlocality
NASA Astrophysics Data System (ADS)
He, Guang Ping
2014-10-01
We simplified our previously proposed quantum bit commitment (QBC) protocol based on the Mach-Zehnder interferometer, by replacing symmetric beam splitters with asymmetric ones. It eliminates the need for random sending time of the photons; thus, the feasibility and efficiency are both improved. The protocol is immune to the cheating strategy in the Mayers-Lo-Chau no-go theorem of unconditionally secure QBC, because the density matrices of the committed states do not satisfy a crucial condition on which the no-go theorem holds.
Generating single-photon catalyzed coherent states with quantum-optical catalysis
NASA Astrophysics Data System (ADS)
Xu, Xue-xiang; Yuan, Hong-chun
2016-07-01
We theoretically generate single-photon catalyzed coherent states (SPCCSs) by means of quantum-optical catalysis based on the beam splitter (BS) or the parametric amplifier (PA). These states are obtained in one of the BS (or PA) output channels if a coherent state and a single-photon Fock state are present in two input ports and a single photon is registered in the other output port. The success probabilities of the detection (also the normalization factors) are discussed, which is different for BS and PA catalysis. In addition, we prove that the generated states catalyzed by BS and PA devices are actually the same quantum states after analyzing photon number distribution of the SPCCSs. The quantum properties of the SPCCSs, such as sub-Poissonian distribution, anti-bunching effect, quadrature squeezing effect, and the negativity of the Wigner function are investigated in detail. The results show that the SPCCSs are non-Gaussian states with an abundance of nonclassicality.
Longitudinal wave function control in single quantum dots with an applied magnetic field
Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A.; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai
2015-01-01
Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots. PMID:25624018
Quantum interference and correlations in single dopants and exchange-coupled dopants in silicon
NASA Astrophysics Data System (ADS)
Salfi, Joe
2015-03-01
Quantum electronics exploiting the highly coherent states of single dopants in silicon invariably requires interactions between states and interfaces, and inter-dopant coupling by exchange interactions. We have developed a low temperature STM scheme for spatially resolved single-electron transport in a device-like environment, providing the first wave-function measurements of single donors and exchange-coupled acceptors in silicon. For single donors, we directly observed valley quantum interference due to linear superpositions of the valleys, and found that valley degrees of freedom are highly robust to the symmetry-breaking perturbation of nearby (3 nm) surfaces. For exchange-coupled acceptors, we measured the singlet-triplet splitting, and from the spatial tunneling probability, extracted enough information about the 2-body wavefunction amplitudes to determine the entanglement entropy, a measure of the quantum inseparability (quantum correlations) generated by the interactions between indistinguishable particles. Entanglement entropy of the J=3/2 holes was found to increase with increasing dopant distance, as Coulomb interactions overcome tunneling, coherently localizing spin towards a Heitler-London singlet, mimicing S=1/2 particles. In the future these capabilities will be exploited to peer into the inner workings of few-dopant quantum devices and shed new light on multi-dopant correlated states, engineered atom-by-atom. Work done collaboratively with J. A. Mol, R. Rahman, G. Klimeck, M. Y. Simmons, L. C. L. Hollenberg, and S. Rogge. Primary financial support from the ARC.
Pons, Thomas; Medintz, Igor L; Farrell, Dorothy; Wang, Xiang; Grimes, Amy F; English, Douglas S; Berti, Lorenzo; Mattoussi, Hedi
2011-07-18
In this report the correlation between the solution photoluminescence (PL) quantum yield and the fluorescence emission of individual semiconductor quantum dots (QDs) is investigated. This is done by taking advantage of previously reported enhancement in the macroscopic quantum yield of water-soluble QDs capped with dihydrolipoic acid (DHLA) when self-assembled with polyhistidine-appended proteins, and by using fluorescence coincidence analysis (FCA) to detect the presence of "bright" and "dark" single QDs in solution. This allows for changes in the fraction of the two QD species to be tracked as the PL yield of the solution is progressively altered. The results clearly indicate that in a dispersion of luminescent nanocrystals, "bright" (intermittently emitting) single QDs coexist with "permanently dark" (non-emitting) QDs. Furthermore, the increase in the fraction of emitting QDs accompanies the increase in the PL quantum yield of the solution. These findings support the idea that a dispersion of QDs consists of two optically distinct populations of nanocrystals--one is "bright" while the other is "dark;" and that the relative fraction of these two populations defines the overall PL yield. PMID:21710484
NASA Astrophysics Data System (ADS)
Zha, Guo-Wei; Shang, Xiang-Jun; Ni, Hai-Qiao; Yu, Ying; Xu, Jian-Xing; Wei, Si-Hang; Ma, Ben; Zhang, Li-Chun; Niu, Zhi-Chuan
2015-09-01
The realization of fiber-output single photon sources is necessary for quantum photonics. Here we present in situ probing and integration of single self-assembled quantum dots (QDs)-in-nanowires. Single self-assembled AlGaAs QDs were synthesized in GaAs/AlGaAs core-shell nanowires by molecular beam epitaxy and characterized by optical excitation in both micro-PL and fiber-integrating set-up. Cascaded biexciton-exciton emission with a saturation signal of 1000 counts per second at nitrogen temperature is achieved through the fiber-integrating setup, which makes single mode fibers an ideal candidate for single photons sources and paves the way for the realization of ‘all fiber’ devices. Numerical calculations were carried out to illustrate the collection efficiency and polarized photoluminescence characteristics. Extraction efficiencies as high as 70% over a broadband emission are reported and increase by a factor of about seven in comparison with air extraction, due to the larger refractive index of the fiber core.
Electrostatic Control of Single IndiumArsenic Quantum Dots using IndiumPhosphorus Nanotemplates
NASA Astrophysics Data System (ADS)
Cheriton, Ross
This thesis focuses on pioneering a scalable route to fabricate quantum information devices based upon single InAs/InP quantum dots emitting in the telecommunications wavelength band around lambda = 1550 nm. Using metallic gates in combination with nanotemplate, site-selective epitaxy techniques, arrays of single quantum dots are produced and electrostatically tuned with a high degree of control over the electrical and optical properties of each individual quantum dot. Using metallic gates to apply local electric fields, the number of electrons within each quantum dot can be tuned and the nature of the optical recombination process controlled. Four electrostatic gates mounted along the sides of a square-based, pyramidal nanotemplate in combination with a flat metallic gate on the back of the InP substrate allow the application of electric fields in any direction across a single quantum dot. Using lateral fields provided by the metallic gates on the sidewalls of the pyramid and a vertical electric field able to control the charge state of the quantum dot, the exchange splitting of the exciton, trion and biexciton are measured as a function of gate voltage. A quadrupole electric field configuration is predicted to symmetrize the product of electron and hole wavefunctions within the dot, producing two degenerate exciton states from the two possible optical decay pathways of the biexciton. Building upon these capabilities, the anisotropic exchange splitting between the exciton states within the biexciton cascade is shown to be reversibly tuned through zero for the first time. We show direct control over the electron and hole wavefunction symmetry, thus enabling the entanglement of emitted photon pairs in asymmetric quantum dots. Optical spectroscopy of single InAs/InP quantum dots atop pyramidal nanotemplates in magnetic fields up to 28T is used to examine the dispersion of the s, p and d shell states. The g-factor and diamagnetic shift of the exciton and charged
Podoshvedov, S. A.
2008-03-15
We study a teleportation protocol of an unknown macroscopic qubit by means of a quantum channel composed of the displaced vacuum and single-photon states. The scheme is based on linear optical devices such as a beam splitter and photon number resolving detectors. A method based on conditional measurement is used to generate both the macroscopic qubit and entangled state composed from displaced vacuum and single-photon states. We show that such a qubit has both macroscopic and microscopic properties. In particular, we investigate a quantum teleportation protocol from a macroscopic object to a microscopic state.
Time-reversal-symmetric single-photon wave packets for free-space quantum communication.
Trautmann, N; Alber, G; Agarwal, G S; Leuchs, G
2015-05-01
Readout and retrieval processes are proposed for efficient, high-fidelity quantum state transfer between a matter qubit, encoded in the level structure of a single atom or ion, and a photonic qubit, encoded in a time-reversal-symmetric single-photon wave packet. They are based on controlling spontaneous photon emission and absorption of a matter qubit on demand in free space by stimulated Raman adiabatic passage. As these processes do not involve mode selection by high-finesse cavities or photon transport through optical fibers, they offer interesting perspectives as basic building blocks for free-space quantum-communication protocols. PMID:25978231
Time-Reversal-Symmetric Single-Photon Wave Packets for Free-Space Quantum Communication
NASA Astrophysics Data System (ADS)
Trautmann, N.; Alber, G.; Agarwal, G. S.; Leuchs, G.
2015-05-01
Readout and retrieval processes are proposed for efficient, high-fidelity quantum state transfer between a matter qubit, encoded in the level structure of a single atom or ion, and a photonic qubit, encoded in a time-reversal-symmetric single-photon wave packet. They are based on controlling spontaneous photon emission and absorption of a matter qubit on demand in free space by stimulated Raman adiabatic passage. As these processes do not involve mode selection by high-finesse cavities or photon transport through optical fibers, they offer interesting perspectives as basic building blocks for free-space quantum-communication protocols.
Single photon transport in two waveguides chirally coupled by a quantum emitter.
Cheng, Mu-Tian; Ma, Xiao-San; Zhang, Jia-Yan; Wang, Bing
2016-08-22
We investigate single photon transport in two waveguides coupled to a two-level quantum emitter (QE). With the deduced analytical scattering amplitudes, we show that under condition of the chiral coupling between the QE and the photon in the two waveguides, the QE can play the role of ideal quantum router to redirect a single photon incident from one waveguide into the other waveguide with a probability of 100% in the ideal condition. The influences of cross coupling between two waveguides and dissipations on the routing are also shown. PMID:27557274
NASA Astrophysics Data System (ADS)
Dey, Swayandipta; Zhou, Yadong; Tian, Xiangdong; Jenkins, Julie A.; Chen, Ou; Zou, Shengli; Zhao, Jing
2015-04-01
In this work, we systematically investigated the plasmonic effect on blinking, photon antibunching behavior and biexciton emission of single CdSe/CdS core/shell quantum dots (QDs) near gold nanoparticles (NPs) with a silica shell (Au@SiO2). In order to obtain a strong interaction between the plasmons and excitons, the Au@SiO2 NPs and CdSe/CdS QDs of appropriate sizes were chosen so that the plasmon resonance overlaps with the absorption and emission of the QDs. We observed that in the regime of a low excitation power, the photon antibunching and blinking properties of single QDs were modified significantly when the QDs were on the Au@SiO2 substrates compared to those on glass. Most significantly, second-order photon intensity correlation data show that the presence of plasmons increases the ratio of the biexciton quantum yield over the exciton quantum yield (QYBX/QYX). An electrodynamics model was developed to quantify the effect of plasmons on the lifetime, quantum yield, and emission intensity of the biexcitons for the QDs. Good agreement was obtained between the experimentally measured and calculated changes in QYBX/QYX due to Au@SiO2 NPs, showing the validity of the developed model. The theoretical studies also indicated that the relative position of the QDs to the Au NPs and the orientation of the electric field are important factors that regulate the emission properties of the excitons and biexcitons of QDs. The study suggests that the multiexciton emission efficiency in QD systems can be manipulated by employing properly designed plasmonic structures.In this work, we systematically investigated the plasmonic effect on blinking, photon antibunching behavior and biexciton emission of single CdSe/CdS core/shell quantum dots (QDs) near gold nanoparticles (NPs) with a silica shell (Au@SiO2). In order to obtain a strong interaction between the plasmons and excitons, the Au@SiO2 NPs and CdSe/CdS QDs of appropriate sizes were chosen so that the plasmon resonance
NASA Astrophysics Data System (ADS)
Geller, Michael R.; Martinis, John M.; Sornborger, Andrew T.; Stancil, Phillip C.; Pritchett, Emily J.; You, Hao; Galiautdinov, Andrei
2015-06-01
Current quantum computing architectures lack the size and fidelity required for universal fault-tolerant operation, limiting the practical implementation of key quantum algorithms to all but the smallest problem sizes. In this work we propose an alternative method for general-purpose quantum computation that is ideally suited for such "prethreshold" superconducting hardware. Computations are performed in the n -dimensional single-excitation subspace (SES) of a system of n tunably coupled superconducting qubits. The approach is not scalable, but allows many operations in the unitary group SU(n ) to be implemented by a single application of the Hamiltonian, bypassing the need to decompose a desired unitary into elementary gates. This feature makes large, nontrivial quantum computations possible within the available coherence time. We show how to use a programmable SES chip to perform fast amplitude amplification and phase estimation, two versatile quantum subalgorithms. We also show that an SES processor is well suited for Hamiltonian simulation, specifically simulation of the Schrödinger equation with a real but otherwise arbitrary n ×n Hamiltonian matrix. We discuss the utility and practicality of such a universal quantum simulator, and propose its application to the study of realistic atomic and molecular collisions.
Huang, Hao; Dorn, August; Nair, Gautham P; Bulović, Vladimir; Bawendi, Moungi G
2007-12-01
We demonstrate reversible quenching of the photoluminescence from single CdSe/ZnS colloidal quantum dots embedded in thin films of the molecular organic semiconductor N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD) in a layered device structure. Our analysis, based on current and charge carrier density, points toward field ionization as the dominant photoluminescence quenching mechanism. Blinking traces from individual quantum dots reveal that the photoluminescence amplitude decreases continuously as a function of increasing forward bias even at the single quantum dot level. In addition, we show that quantum dot photoluminescence is quenched by aluminum tris(8-hydroxyquinoline) (Alq3) in chloroform solutions as well as in thin solid films of Alq3 whereas TPD has little effect. This highlights the importance of chemical compatibility between semiconductor nanocrystals and surrounding organic semiconductors. Our study helps elucidate elementary interactions between quantum dots and organic semiconductors, knowledge needed for designing efficient quantum dot organic optoelectronic devices. PMID:18034504