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Author (down) Stucki, Damien; Barreiro, Claudio; Fasel, Sylvain; Gautier, Jean-Daniel; Gay, Olivier; Gisin, Nicolas; Thew, Rob; Thoma, Yann; Trinkler, Patrick; Vannel, Fabien; Zbinden, Hugo
Title Continuous high speed coherent one-way quantum key distribution Type Journal Article
Year 2009 Publication Optics Express Abbreviated Journal Opt. Express
Volume 17 Issue 16 Pages 13326-13334
Keywords quantum cryptography, QKD, PNS, SSPD, coherent one way, COW
Abstract Quantum key distribution (QKD) is the first commercial quantum technology operating at the level of single quanta and is a leading light for quantum-enabled photonic technologies. However, controlling these quantum optical systems in real world environments presents significant challenges. For the first time, we have brought together three key concepts for future QKD systems: a simple high-speed protocol; high performance detection; and integration both, at the component level and for standard fibre network connectivity. The QKD system is capable of continuous and autonomous operation, generating secret keys in real time. Laboratory and field tests were performed and comparisons made with robust InGaAs avalanche photodiodes and superconducting detectors. We report the first real world implementation of a fully functional QKD system over a 43dB-loss (150km) transmission line in the Swisscom fibre optic network where we obtained average real-time distribution rates over 3 hours of 2.5bps.
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Call Number RPLAB @ akorneev @ Serial 602
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Author (down) Stucki, D.; Walenta, N.; Vannel, F.; Thew, R.T.; Gisin, N.; Zbinden, H.; Gray, S.; Towery, C. R.; Ten, S.
Title High rate long-distance quantum key distribution over 250 km of ultra low loss fibres Type Journal Article
Year 2009 Publication New J. Phys. Abbreviated Journal
Volume 11 Issue 7 Pages 075003
Keywords SSPD, quantum cryptography, QKD, COW
Abstract We present a fully automated quantum key distribution prototype running at 625 MHz clock rate. Taking advantage of ultra low loss fibres and low-noise superconducting detectors, we can distribute 6,000 secret bits per second over 100 km and 15 bits per second over 250km.
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Call Number RPLAB @ akorneev @ Serial 610
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Author (down) Smirnov, K. V.; Vakhtomin, Yu. B.; Divochiy, A. V.; Ozhegov, R. V.; Pentin, I. V.; Slivinskaya, E. V.; Tarkhov, M. A.; Gol’tsman, G. N.
Title Single-photon detectors for the visible and infrared parts of the spectrum based on NbN nanostructures Type Abstract
Year 2009 Publication Proc. Progress In Electromagnetics Research Symp. Abbreviated Journal Proc. Progress In Electromagnetics Research Symp.
Volume Issue Pages 863-864
Keywords SSPD, SNSPD
Abstract The research by the group of Moscow State Pedagogical University into the hot-electron phenomena in thin superconducting films has led to the development of new types ofdetectors [1, 2] and their use both in fundamental and applied studies [3–6]. In this paper, wepresent the results of the development and fabrication of receiving systems for the visible andinfrared parts of the spectrum optimised for use in telecommunication systems and quantumcryptography.
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Publisher Place of Publication Moscow, Russia Editor
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Notes Approved no
Call Number RPLAB @ sasha @ smirnovsession Serial 1050
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Author (down) Shor, Peter W.
Title Quantum information theory: The bits don't add up Type Journal Article
Year 2009 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 5 Issue Pages 247 - 248
Keywords fromIPMRAS
Abstract A counterexample to the 'additivity question', the most celebrated open problem in the mathematical theory of quantum information, casts doubt on the possibility of finding a simple expression for the information capacity of a quantum channel.
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Call Number RPLAB @ gujma @ Serial 800
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Author (down) Sekine, Norihiko; Hosako, Iwao
Title Intensity modulation of terahertz quantum cascade lasers under external light injection Type Journal Article
Year 2009 Publication Applied Physics Letters Abbreviated Journal Appl. Phys. Lett.
Volume 95 Issue Pages 201106(1-3)
Keywords QCL modulation, THz, terahertz
Abstract We investigated the light-current characteristics of terahertz (THz) quantum cascade lasers under external light injection, which excites interband transitions in the active materials. It was found that the amount of reduction in the THz power was constant for all injection currents above threshold, and the dependence of the reduction amount on the wavelength of the external light was observed to show a resonancelike feature. The dominant intensity modulation mechanism was found to be the loss change caused by interband transitions in the active region. Further, the effective coupling efficiency plays an important role in the intensity modulation.
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Notes Approved no
Call Number Serial 630
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Author (down) Scheel, Stefan
Title Single-photon sources–an introduction Type Journal Article
Year 2009 Publication J. Modern Opt. Abbreviated Journal
Volume 56 Issue 2-3 Pages 141-160
Keywords LOQC; quantum cryptography; QKD
Abstract This review surveys the physical principles and recent developments in manufacturing single-photon sources. Special emphasis is placed on important potential applications such as linear optical quantum computing (LOQC), quantum key distribution (QKD) and quantum metrology that drive the development of these sources of single photons. We discuss the quantum-mechanical properties of light prepared in a quantum state of definite photon number and compare it with coherent light that shows a Poissonian distribution of photon numbers. We examine how the single-photon fidelity directly influences the ability to transmit secure quantum bits over a predefined distance. The theoretical description of modified spontaneous decay, the main principle behind single-photon generation, provides the background for many experimental implementations such as those using microresonators or pillar microcavities. The main alternative way to generate single photons using postselection of entangled photon pairs from parametric down-conversion, will be discussed. We concentrate on describing the underlying physical principles and we will point out limitations and open problems associated with single-photon production.
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Call Number RPLAB @ gujma @ Serial 669
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Author (down) Sahu, Mitrabhanu; Bae, Myung-Ho; Rogachev, Andrey; Pekker, David; Wei, Tzu-Chieh; Shah, Nayana; Goldbart, Paul M.; Bezryadin, Alexey
Title Individual topological tunnelling events of a quantum field probed through their macroscopic consequences Type Journal Article
Year 2009 Publication Nature Phys. Abbreviated Journal Nature Phys.
Volume 5 Issue Pages 503-508
Keywords phase slips, superconducting nanowires
Abstract Phase slips are topological fluctuations that carry the superconducting order-parameter field between distinct current-carrying states. Owing to these phase slips, superconducting nanowires acquire electrical resistance. In such wires, it is well known that at higher temperatures phase slips occur through the process of thermal barrier-crossing by the order-parameter field. At low temperatures, the general expectation is that phase slips should proceed through quantum tunnelling events, which are known as quantum phase slips. However, resistive measurements have produced evidence both for and against the occurrence of quantum phase slips. Here, we report evidence for the observation of individual quantum phase-slip events in homogeneous ultranarrow wires at high bias currents. We accomplish this through measurements of the distribution of switching currents for which the width exhibits a rather counter-intuitive, monotonic increase with decreasing temperature. Importantly, measurements show that in nanowires with larger critical currents, quantum fluctuations dominate thermal fluctuations up to higher temperatures.
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Notes Recommended by Klapwijk Approved no
Call Number Serial 928
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Author (down) Ryabchun, Sergey; Tong, Cheuk-Yu Edward; Paine, Scott; Lobanov, Yury; Blundell, Raymond; Goltsman, Gregory
Title Temperature resolution of an HEB receiver at 810 GHz Type Journal Article
Year 2009 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume 19 Issue 3 Pages 293-296
Keywords HEB mixer
Abstract We present the results of direct measurements of the temperature resolution of an HEB receiver operating at 810 GHz, in both continuum and spectroscopic modes. In the continuum mode, the input of the receiver was switched between black bodies with different physical temperatures. With a system noise temperature of around 1100 K, the receiver was able to resolve loads which differed in temperature by about 1 K over an integration time of 5 seconds. This resolution is significantly worse than the value of 0.07 K given by the radiometer equation. In the spectroscopic mode, a gas cell filled with carbonyl sulphide (OCS) gas was used and the emission line at 813.3537060 GHz was measured using the receiver in conjunction with a digital spectrometer. From the observed spectra, we determined that the measurement uncertainty of the equivalent emission temperature was 2.8 K for an integration time of 0.25 seconds and a spectral resolution of 12 MHz, compared to a 1.4 K temperature resolution given by the radiometer equation. This relative improvement is due to the fact that at short integration times the contribution from 1/f noise and drift are less dominant. In both modes, the temperature resolution was improved by about 40% with the use of a feedback loop which adjusted the level of an injected microwave radiation to maintain a constant operating current of the HEB mixer. This stabilization scheme has proved to be very effective to keep the temperature resolution of the HEB receiver to close to the theoretical value given by the radiometer equation.
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Notes Approved no
Call Number Serial 636
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Author (down) Ryabchun, Sergey; Tong, Cheuk-Yu Edward; Blundell, Raymond; Gol'tsman, Gregory
Title Stabilization scheme for hot-electron bolometer receivers using microwave radiation Type Journal Article
Year 2009 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume 19 Issue 1 Pages 14-19
Keywords HEB, mixer, Allan variance, stabilization, radiometer equation
Abstract We present the results of a stabilization scheme for terahertz receivers based on NbN hot-electron bolometer (HEB) mixers that uses microwave radiation with a frequency much lower than the gap frequency of NbN to compensate for mixer current fluctuations. A feedback control loop, which actively controls the power level of the injected microwave radiation, has successfully been implemented to stabilize the operating point of the HEB mixer. This allows us to increase the receiver Allan time to 10 s and also improve the temperature resolution of the receiver by about 30% in the total power mode of operation.
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ISSN 1051-8223 ISBN Medium
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Notes Approved no
Call Number RPLAB @ lobanovyury @ Serial 559
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Author (down) Ryabchun, S. A.; Tretyakov, I. V.; Pentin, I. V.; Kaurova, N. S.; Seleznev, V. A.; Voronov, B. M.; Finkel, M. I.; Maslennikov, S. N.; Gol'tsman, G. N.
Title Low-noise wide-band hot-electron bolometer mixer based on an NbN film Type Journal Article
Year 2009 Publication Radiophys. Quant. Electron. Abbreviated Journal
Volume 52 Issue 8 Pages 576-582
Keywords HEB mixer, in-situ contacts, noise temperature, conversion gain bandwidth, diffusion cooling channel
Abstract We develop and study a hot-electron bolometer mixer made of a two-layer NbN–Au film in situ deposited on a silicon substrate. The double-sideband noise temperature of the mixer is 750 K at a frequency of 2.5 THz. The conversion efficiency measurements show that at the superconducting transition temperature, the intermediate-frequency bandwidth amounts to about 6.5 GHz for a mixer 0.112 μm long. These record-breaking characteristics are attributed to the improved contacts between a sensitive element and a helical antenna and are reached due to using the in situ deposition of NbN and Au layers at certain stages of the process.
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Notes Approved no
Call Number Serial 599
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