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Author Kim, Yong-Su; Lee, Jong-Chan; Kwon, Osung; Kim, Yoon-Ho
Title Protecting entanglement from decoherence using weak measurement and quantum measurement reversal Type Journal Article
Year (down) 2012 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 8 Issue 2 Pages 117-120
Keywords fromIPMRAS
Abstract Decoherence, often caused by unavoidable coupling with the environment, leads to degradation of quantum coherence. For a multipartite quantum system, decoherence leads to degradation of entanglement and, in certain cases, entanglement sudden death. Tackling decoherence, thus, is a critical issue faced in quantum information, as entanglement is a vital resource for many quantum information applications including quantum computing, quantum cryptography, quantum teleportation and quantum metrology. Here, we propose and demonstrate a scheme to protect entanglement from decoherence. Our entanglement protection scheme makes use of the quantum measurement itself for actively battling against decoherence and it can effectively circumvent even entanglement sudden death.
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Call Number RPLAB @ gujma @ Serial 815
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Author Julia Toussaint, Roman Grüner, Marco Schubert, Torsten May, Hans-Georg Meyer, Benjamin Dietzek, Jürgen Popp, Matthias Hofherr, Matthias Arndt, Dagmar Henrich, Konstantin Il'in, and Michael Siegel
Title Superconducting single-photon counting system for optical experiments requiring time-resolution in the picosecond range Type Journal Article
Year (down) 2012 Publication Abbreviated Journal AIP REVIEW OF SCIENTIFIC INSTRUMENTS
Volume 83 Issue Pages
Keywords SSPD, picosecond, time-resolution
Abstract We have developed a cryogenic measurement system for single-photon counting, which can be used

in optical experiments requiring high time resolution in the picosecond range. The system utilizes

niobium nitride superconducting nanowire single-photon detectors which are integrated in a timecorrelated

single-photon counting (TCSPC) setup. In this work, we describe details of the mechanical

design, the electrical setup, and the cryogenic optical components. The performance of the complete

system in TCSPC mode is tentatively benchmarked using 140 fs long laser pulses at a repetition

frequency of 75MHz. Due to the high temporal stability of these pulses, the measured time resolution

of 35 ps (FWHM) is limited by the timing jitter of the measurement system. The result was crosschecked

in a Coherent Anti-stokes Raman Scattering (CARS) setup, where scattered pulses from a

β-barium borate crystal have been detected with the same time resolution.
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Call Number RPLAB @ seleznev @ Serial 885
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Author Engel, Andreas; Aeschbacher, Adrian; Inderbitzin, Kevin; Schilling, Andreas; Il'in, Konstantin; Hofherr, Matthias; Siegel, Michael; Semenov, Alexei; Hübers, Heinz-Wilhelm
Title Tantalum nitride superconducting single-photon detectors with low cut-off energy Type Journal Article
Year (down) 2011 Publication arXiv Abbreviated Journal arXiv
Volume Issue Pages 9
Keywords SSPD
Abstract Materials with a small superconducting energy gap favor a high detection efficiency of low-energy photons in superconducting nanowire single-photon detectors. We developed a TaN detector with smaller gap and lower density of states at the Fermi energy than in comparable NbN devices, while other relevant parameters remain essentially unchanged. This results in a reduction of the minimum photon energy required for direct detection to $\approx1/3$ as compared to NbN.
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Publisher Place of Publication arXiv:1110.4576 Editor
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Call Number RPLAB @ gujma @ Serial 687
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Author Lobanov, Y.V.; Tong, C.-Y.E.; Hedden, A.S.; Blundell, R.; Voronov, B.M.; Gol'tsman, G.N.
Title Direct measurement of the gain and noise bandwidths of HEB mixers Type Journal Article
Year (down) 2011 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume 21 Issue 3 Pages 645-648
Keywords waveguide NbN HEB mixers
Abstract The intermediate frequency (IF) bandwidth of a hot electron bolometer (HEB) mixer is an important parameter of the mixer, in that it helps to determine its suitability for a given application. With the availability of wideband low noise amplifiers, it is simple to measure the performance of an HEB mixer over a wide range of IF at a fixed LO frequency using the standard Y-factor method. This in-situ method allows us to measure both the gain and noise bandwidths simultaneously. We have also measured mixer output impedance with a vector network analyser. Intrinsic time constant has been extracted from the impedance data and compared to the mixer's bandwidths determined from receiver Y-factor measurement.
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Call Number RPLAB @ gujma @ Serial 720
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Author Huang, Kevin C. Y.; Jun, Young Chul; Seo, Min-Kyo; Brongersma, Mark L.
Title Power flow from a dipole emitter near an optical antenna Type Journal Article
Year (down) 2011 Publication Optics Express Abbreviated Journal Opt. Express
Volume 19 Issue 20 Pages 19084-19092
Keywords optical antennas
Abstract Current methods to calculate the emission enhancement of a quantum emitter coupled to an optical antenna of arbitrary geometry rely on analyzing the total Poynting vector power flow out of the emitter or the dyadic Green functions from full-field numerical simulations. Unfortunately, these methods do not provide information regarding the nature of the dominant energy decay pathways. We present a new approach that allows for a rigorous separation, quantification, and visualization of the emitter output power flow captured by an antenna and the subsequent reradiation power flow to the far field. Such analysis reveals unprecedented details of the emitter/antenna coupling mechanisms and thus opens up new design strategies for strongly interacting emitter/antenna systems used in sensing, active plasmonics and metamaterials, and quantum optics.
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Call Number RPLAB @ gujma @ Serial 743
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