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Author Arcizet, O.; Jacques, V.; Siria, A.; Poncharal, P.; Vincent, P.; Seidelin, S.
Title A single nitrogen-vacancy defect coupled to a nanomechanical oscillator Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue (down) 11 Pages 879-883
Keywords fromIPMRAS
Abstract We position a single nitrogen-vacancy (NV) centre hosted in a diamond nanocrystal at the extremity of a SiC nanowire. This novel hybrid system couples the degrees of freedom of two radically different systems: a nanomechanical oscillator and a single quantum object. We probe the dynamics of the nano-resonator through time-resolved nanocrystal fluorescence and photon-correlation measurements, conveying the influence of a mechanical degree of freedom on a non-classical photon emitter. Moreover, by immersing the system in a strong magnetic field gradient, we induce a magnetic coupling between the nanomechanical oscillator and the NV electronic spin, providing nanomotion readout through a single electronic spin. Spin-dependent forces inherent to this coupling scheme are essential in a variety of active cooling and entanglement protocols used in atomic physics, and should now be within the reach of nanomechanical hybrid systems.
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Call Number RPLAB @ gujma @ Serial 819
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Author Манова, Н.Н.; Корнеева, Ю.П.; Корнеев, А.А.; Слыш, В.; Воронов, Б.М.; Гольцман, Г.Н.
Title Сверхпроводниковый NbN однофотонный детектор, интегрированный с четвертьволновым резонатором Type Journal Article
Year 2011 Publication Письма в Журнал технической физики Abbreviated Journal ПЖТФ
Volume 37 Issue (down) 10 Pages 7
Keywords SSPD
Abstract Исследована спектральная зависимость квантовой эффективности сверхпроводниковых NbN однофотонных детекторов, интегрированных с оптическими четвертьволновыми резонаторами с использованием диэлектриков Si3N4, SiO2, SiO.
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Call Number RPLAB @ gujma @ Serial 637
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Author Miller, Aaron J.; Lita, Adriana E.; Calkins, Brice; Vayshenker, Igor; Gruber, Steven M.; Nam, Sae Woo
Title Compact cryogenic self-aligning fiber-to-detector coupling with losses below one percent Type Journal Article
Year 2011 Publication Optics Express Abbreviated Journal Opt. Express
Volume 19 Issue (down) 10 Pages 9102-9110
Keywords TES
Abstract We present a compact packaging technique for coupling light from a single-mode telecommunication fiber to cryogenic single-photon sensitive devices. Our single-photon detectors are superconducting transition-edge sensors (TESs) with a collection area only a factor of a few larger than the area of the fiber core which presents significant challenges to low-loss fiber-to-detector coupling. The coupling method presented here has low loss, cryogenic compatibility, easy and reproducible assembly and low component cost. The system efficiency of the packaged single-photon counting detectors is verified by the “triplet method” of power-source calibration along with the “multiple attenuator” method that produces a calibrated single-photon flux. These calibration techniques, when used in combination with through-wafer imaging and fiber back-reflection measurements, give us confidence that we have achieved coupling losses below 1 % for all devices packaged according to the self-alignment method presented in this paper.
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Call Number RPLAB @ gujma @ Serial 666
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Author Prevedel, Robert; Hamel, Deny R.; Colbeck, Roger; Fisher, Kent; Resch, Kevin J.
Title Experimental investigation of the uncertainty principle in the presence of quantum memory and its application to witnessing entanglement Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue (down) 10 Pages 757-761
Keywords fromIPMRAS
Abstract Heisenberg's uncertainty principle provides a fundamental limitation on the ability of an observer holding classical information to predict the outcome when one of two measurements is performed on a quantum system. However, an observer with access to a particle (stored in a quantum memory) which is entangled with the system generally has a reduced uncertainty: indeed, if the particle and system are maximally entangled, the observer can perfectly predict the outcome of whichever measurement is chosen. This effect has recently been quantified in a new entropic uncertainty relation. Here we experimentally investigate this relation, showing its effectiveness as an efficient entanglement witness. We use entangled photon pairs, an optical delay line serving as a simple quantum memory and fast, active feed-forward. Our results quantitatively agree with the new uncertainty relation. Our technique acts as a witness for almost all entangled states in our experiment as we obtain lower uncertainties than would be possible without the entangled particle.
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Call Number RPLAB @ gujma @ Serial 821
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Author Fuchs, G. D.; Burkard, G.; Klimov, P. V.; Awschalom, D. D.
Title A quantum memory intrinsic to single nitrogen–vacancy centres in diamond Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue (down) 10 Pages 789-793
Keywords fromIPMRAS
Abstract A quantum memory, composed of a long-lived qubit coupled to each processing qubit, is important to building a scalable platform for quantum information science. These two qubits should be connected by a fast and high-fidelity operation to store and retrieve coherent quantum states. Here, we demonstrate a room-temperature quantum memory based on the spin of the nitrogen nucleus intrinsic to each nitrogen–vacancy (NV) centre in diamond. We perform coherent storage of a single NV centre electronic spin in a single nitrogen nuclear spin using Landau–Zener transitions across a hyperfine-mediated avoided level crossing. By working outside the asymptotic regime, we demonstrate coherent state transfer in as little as 120 ns with total storage fidelity of 88±6%. This work demonstrates the use of a quantum memory that is compatible with scaling as the nitrogen nucleus is deterministically present in each NV centre defect.
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Call Number RPLAB @ gujma @ Serial 823
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Author Hosseini, M.; Campbell, G.; Sparkes, B. M.; Lam, P. K.; Buchler, B. C.
Title Unconditional room-temperature quantum memory Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue (down) 10 Pages 794-798
Keywords fromIPMRAS
Abstract Just as classical information systems require buffers and memory, the same is true for quantum information systems. The potential that optical quantum information processing holds for revolutionizing computation and communication is therefore driving significant research into developing optical quantum memory. A practical optical quantum memory must be able to store and recall quantum states on demand with high efficiency and low noise. Ideally, the platform for the memory would also be simple and inexpensive. Here, we present a complete tomographic reconstruction of quantum states that have been stored in the ground states of rubidium in a vapour cell operating at around 80 °C. Without conditional measurements, we show recall fidelity up to 98% for coherent pulses containing around one photon. To unambiguously verify that our memory beats the quantum no-cloning limit we employ state-independent verification using conditional variance and signal-transfer coefficients.
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Call Number RPLAB @ gujma @ Serial 824
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Author Semenov, A. V.; Devyatov, I. A.; Ryabchun, S. A.; Maslennikov, S. N.; Maslennikova, A. S.; Larionov, P. A.; Voronov, B. M.; Chulkova, G. M.
Title Absorption of terahertz electromagnetic radiation in dirty superconducting film at arbitrary type of the spectral functions Type Journal Article
Year 2011 Publication Rus. J. Radio Electron. Abbreviated Journal Rus. J. Radio Electron.
Volume Issue (down) 10 Pages
Keywords terahertz electromagnetic radiation; superconductors; detectors of terahertz range
Abstract A problem of absorption of high-frequency electromagnetic field in dirty superconductor is treated within Keldysh technic. Expression for the source term in the kinetic equation for quasiparticle distribution function is derived. The result is significant for deriving a consistent microscopic theory of superconducting detectors for terahertz frequency range, perspective detectors on kinetic inductance of current-biased superconducting strip and on Josephson inductance of tunnel.
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Notes 7 pages Approved no
Call Number Serial 1117
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Author Mitin, Vladimir; Antipov, Andrei; Sergeev, Andrei; Vagidov, Nizami; Eason, David; Strasser, Gottfried
Title Quantum Dot Infrared Photodetectors: Photoresponse Enhancement Due to Potential Barriers Type Journal Article
Year 2011 Publication Nanoscale Research Letters Abbreviated Journal Nanoscale res lett
Volume 6 Issue (down) 1 Pages 6
Keywords Quantum dots; Infrared detectors; Photoresponse; Doping; Potential barriers; Capture processes
Abstract Potential barriers around quantum dots (QDs) play a key role in kinetics of photoelectrons. These barriers are always created, when electrons from dopants outside QDs fill the dots. Potential barriers suppress the capture processes of photoelectrons and increase the photoresponse. To directly investigate the effect of potential barriers on photoelectron kinetics, we fabricated several QD structures with different positions of dopants and various levels of doping. The potential barriers as a function of doping and dopant positions have been determined using nextnano3 software. We experimentally investigated the photoresponse to IR radiation as a function of the radiation frequency and voltage bias. We also measured the dark current in these QD structures. Our investigations show that the photoresponse increases ~30 times as the height of potential barriers changes from 30 to 130 meV.
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Call Number RPLAB @ gujma @ Serial 712
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Author Wiechers, C.; Lydersen, L.; Wittmann, C.; Elser, D.; Skaar, J.; Marquardt, Ch; Makarov, V.; Leuchs, G.
Title After-gate attack on a quantum cryptosystem Type Journal Article
Year 2011 Publication New J. Phys. Abbreviated Journal
Volume 13 Issue (down) 1 Pages 14
Keywords quantum cryptography; hacking; interception; attack; SPD; APD; QKD
Abstract We present a method to control the detection events in quantum key distribution systems that use gated single-photon detectors. We employ bright pulses as faked states, timed to arrive at the avalanche photodiodes outside the activation time. The attack can remain unnoticed, since the faked states do not increase the error rate per se. This allows for an intercept-resend attack, where an eavesdropper transfers her detection events to the legitimate receiver without causing any errors. As a side effect, afterpulses, originating from accumulated charge carriers in the detectors, increase the error rate. We have experimentally tested detectors of the system id3110 (Clavis2) from ID Quantique. We identify the parameter regime in which the attack is feasible despite the side effect. Furthermore, we outline how simple modifications in the implementation can make the device immune to this attack.
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Call Number RPLAB @ gujma @ Serial 730
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Author Hu, Xiaolong; Dauler, Eric A.; Molnar, Richard J.; Berggren, Karl K.
Title Superconducting nanowire single-photon detectors integrated with optical nano-antennae Type Journal Article
Year 2011 Publication Optics Express Abbreviated Journal Opt. Express
Volume 19 Issue (down) 1 Pages 17-31
Keywords optical antennas
Abstract Optical nano-antennae have been integrated with semiconductor lasers to intensify light at the nanoscale and photodiodes to enhance photocurrent. In quantum optics, plasmonic metal structures have been used to enhance nonclassical light emission from single quantum dots. Absorption and detection of single photons from free space could also be enhanced by nanometallic antennae, but this has not previously been demonstrated. Here, we use nano-optical transmission effects in a one-dimensional gold structure, combined with optical cavity resonance, to form optical nano-antennae, which are further used to couple single photons from free space into a 80-nm-wide superconducting nanowire. This antenna-assisted coupling enables a superconducting nanowire single-photon detector with 47% device efficiency at the wavelength of 1550 nm and 9-μm-by-9-μm active area while maintaining a reset time of only 5 ns. We demonstrate nanoscale antenna-like structures to achieve exceptional efficiency and speed in single-photon detection.
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Call Number RPLAB @ gujma @ Serial 745
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Author Zhu, J.; Christensen, J.; Jung, J.; Martin-Moreno, L.; Yin, X.; Fok, L.; Zhang, X.; Garcia-Vidal, F. J.
Title A holey-structured metamaterial for acoustic deep-subwavelength imaging Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue (down) 1 Pages 52-55
Keywords fromIPMRAS
Abstract For classical waves such as light or sound, diffraction sets a natural limit on how finely the details of an object can be recorded on its image. Recently, various optical superlenses based on the metamaterials concept have shown the possibility of overcoming the diffraction limit. Similar two-dimensional (2D) acoustic hyperlens designs have also been explored. Here we demonstrate a 3D holey-structured metamaterial that achieves acoustic imaging down to a feature size of λ/50. The evanescent field components of a subwavelength object are efficiently transmitted through the structure as a result of their strong coupling with Fabry-Pérot resonances inside the holey plate. This capability of acoustic imaging at a very deep-subwavelength scale may open the door for a broad range of applications, including medical ultrasonography, underwater sonar and ultrasonic non-destructive evaluation.
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Call Number RPLAB @ gujma @ Serial 809
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Author Kumar, Sushil; Chan, Chun Wang I.; Hu, Qing; Reno, John L.
Title A 1.8-THz quantum cascade laser operating significantly above the temperature of hw/k Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal
Volume 7 Issue (down) Pages 166-171
Keywords QCL, 2 mW at 155 K and 1.8 THz
Abstract Several competing technologies continue to advance the field of terahertz science; of particular importance has been the development of a terahertz semiconductor quantum cascade laser (QCL), which is arguably the only solid-state terahertz source with average optical power levels of much greater than a milliwatt. Terahertz QCLs are required to be cryogenically cooled and improvement of their temperature performance is the single most important research goal in the field. Thus far, their maximum operating temperature has been empirically limited to ~planckω/kB, a largely inexplicable trend that has bred speculation that a room-temperature terahertz QCL may not be possible in materials used at present. Here, we argue that this behaviour is an indirect consequence of the resonant-tunnelling injection mechanism employed in all previously reported terahertz QCLs. We demonstrate a new scattering-assisted injection scheme to surpass this limit for a 1.8-THz QCL that operates up to ~1.9planckω/kB (163 K). Peak optical power in excess of 2 mW was detected from the laser at 155 K. This development should make QCL technology attractive for applications below 2 THz, and initiate new design strategies for realizing a room-temperature terahertz semiconductor laser.
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Call Number Serial 631
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Author Tretyakov, Ivan; Ryabchun, Sergey; Finkel, Matvey; Maslennikova, Anna; Kaurova, Natalia; Lobastova, Anastasia; Voronov, Boris; Gol'tsman, Gregory
Title Low noise and wide bandwidth of NbN hot-electron bolometer mixers Type Journal Article
Year 2011 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.
Volume 98 Issue (down) Pages 033507 (1 to 3)
Keywords NbN HEB mixer
Abstract We report a record double sideband noise temperature of 600 K (5hν/kB) offered by a NbN hot-electron bolometer receiver at 2.5 THz. Allowing for standing wave effects, this value was found to be constant in the intermediate frequency range 1–7 GHz, which indicates that the mixer has an unprecedentedly large noise bandwidth in excess of 7 GHz. The insight into this is provided by gain bandwidth measurements performed at the superconducting transition. They show that the dependence of the bandwidth on the mixer length follows the model for an HEB mixer with diffusion and phonon cooling of the hot electrons.
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Call Number RPLAB @ gujma @ Serial 638
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Author Pernice, W.; Schuck, C.; Li, M.; Goltsman, G. N.; Sergienko, A. V.; Tang, H. X.
Title High speed travelling wave single-photon detectors with near-unity quantum efficiency Type Journal Article
Year 2011 Publication arXiv Abbreviated Journal arXiv
Volume Issue (down) Pages 1-14
Keywords SPD
Abstract Ultrafast, high quantum efficiency single photon detectors are among the most sought-after elements in modern quantum optics and quantum communication. Close-to-unity photon detection efficiency is essential for scalable measurement-based quantum computation, quantum key distribution, and loophole-free Bell experiments. However, imperfect modal matching and finite photon absorption rates have usually limited the maximum attainable detection efficiency of single photon detectors. Here we demonstrate a superconducting nanowire detector atop nanophotonic waveguides and achieve single photon detection efficiency up to 94% at telecom wavelengths. Our detectors are fully embedded in a scalable, low loss silicon photonic circuit and provide ultrashort timing jitter of 18ps at multi-GHz detection rates. Exploiting this high temporal resolution we demonstrate ballistic photon transport in silicon ring resonators. The direct implementation of such a detector with high quantum efficiency, high detection speed and low jitter time on chip overcomes a major barrier in integrated quantum photonics.
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Publisher Place of Publication arXiv:1108.5299 Editor
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Call Number RPLAB @ gujma @ Serial 661
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Author Beck, M.; Klammer, M.; Lang, S.; Leiderer, P.; Kabanov, V. V.; Gol’tsman, G. N.; Demsar, J.
Title Energy-gap dynamics of superconducting NbN thin films studied by time-resolved terahertz spectroscopy Type Miscellaneous
Year 2011 Publication arXiv Abbreviated Journal
Volume Issue (down) Pages
Keywords NbN thin film, energy gap dynamics
Abstract Using time-domain Terahertz spectroscopy we performed direct studies of the photoinduced suppression and recovery of the superconducting gap in a conventional BCS superconductor NbN. Both processes are found to be strongly temperature and excitation density dependent. The analysis of the data with the established phenomenological Rothwarf-Taylor model enabled us to determine the bare quasiparticle recombination rate, the Cooper pair-breaking rate and the electron-phonon coupling constant, \lambda = 1.1 +/- 0.1, which is in excellent agreement with theoretical estimates.
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Notes Duplicated as 641 Approved no
Call Number Serial 1388
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