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Author Bell, M.; Sergeev, A.; Mitin, V.; Bird, J.; Verevkin, A.; Gol’tsman, G. url  doi
openurl 
  Title One-dimensional resistive states in quasi-two-dimensional superconductors: Experiment and theory Type Journal Article
  Year 2007 Publication Phys. Rev. B Abbreviated Journal Phys. Rev. B  
  Volume 76 Issue 9 Pages 094521 (1 to 5)  
  Keywords uasi-two-dimensional superconductors, NbN  
  Abstract (up) We investigate competition between one- and two-dimensional topological excitations—phase slips and vortices—in the formation of resistive states in quasi-two-dimensional superconductors in a wide temperature range below the mean-field transition temperature TC0. The widths w=100nm of our ultrathin NbN samples are substantially larger than the Ginzburg-Landau coherence length ξ=4nm, and the fluctuation resistivity above TC0 has a two-dimensional character. However, our data show that the resistivity below TC0 is produced by one-dimensional excitations—thermally activated phase slip strips (PSSs) overlapping the sample cross section. We also determine the scaling phase diagram, which shows that even in wider samples the PSS contribution dominates over vortices in a substantial region of current and/or temperature variations. Measuring the resistivity within 7 orders of magnitude, we find that the quantum phase slips can only be essential below this level.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1098-0121 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1423  
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Author Kerman, A. J.; Dauler, E. A.; Yang, J. K. W.; Rosfjord, K. M.; Anant, V.; Berggren, K. K.; Gol’tsman, G. N.; Voronov, B. M. url  doi
openurl 
  Title Constriction-limited detection efficiency of superconducting nanowire single-photon detectors Type Journal Article
  Year 2007 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.  
  Volume 90 Issue 10 Pages 101110 (1 to 3)  
  Keywords SSPD, SNSPD  
  Abstract (up) We investigate the source of the large variations in the observed detection efficiencies of superconducting nanowire single-photon detectors between many nominally identical devices. Through both electrical and optical measurements, we infer that these variations arise from “constrictions:” highly localized regions of the nanowires where the effective cross-sectional area for superconducting current is reduced. These constrictions limit the bias-current density to well below its critical value over the remainder of the wire, and thus prevent the detection efficiency from reaching the high values that occur in these devices when they are biased near the critical current density.

This work is sponsored by the United States Air Force under Contract No. FA8721-05-C-0002.
 
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0003-6951 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1433  
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Author Yang, J. K. W.; Kerman, A. J.; Dauler, E. A.; Anant, V.; Rosfjord, K. M.; Berggren, K. K. openurl 
  Title Modeling the electrical and thermal response of superconducting nanowire single-photon detectors Type Journal Article
  Year 2007 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal  
  Volume 17 Issue 2 Pages 581 - 585  
  Keywords SSPD, modeling  
  Abstract (up) We modeled the response of superconducting nanowire single-photon detectors during a photodetection event, taking into consideration only the thermal and electrical properties of a superconducting NbN nanowire on a sapphire substrate. Our calculations suggest that heating which occurs after the formation of a photo-induced resistive barrier is responsible for the generation of a measurable voltage pulse. We compared this numerical result with experimental data of a voltage pulse from a slow device, i.e. large kinetic inductance, and obtained a good fit. Using this electro-thermal model, we estimated the temperature rise and the resistance buildup in the nanowire, and the return current at which the nanowire becomes superconducting again. We also show that the reset time of these photodetectors can be decreased by the addition of a series resistance and provide supporting experimental data. Finally we present preliminary results on a detector latching behavior that can also be explained using the electro-thermal model.  
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  Notes Approved no  
  Call Number Serial 625  
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Author Słysz, W.; Wegrzecki, M.; Bar, J.; Grabiec, P.; Górska, M.; Zwiller, V.; Latta, C.; Böhi, P.; Pearlman, A.J.; Cross, A.S.; Pan, D.; Kitaygorsky, J.; Komissarov, I.; Verevkin, A.; Milostnaya, I.; Korneev, A.; Minayeva, O.; Chulkova, G.; Smirnov, K.; Voronov, B.; Gol’tsman, G.N.; Sobolewski, R. url  doi
openurl 
  Title Fibre-coupled, single photon detector based on NbN superconducting nanostructures for quantum communications Type Journal Article
  Year 2007 Publication J. Modern Opt. Abbreviated Journal J. Modern Opt.  
  Volume 54 Issue 2-3 Pages 315-326  
  Keywords NbN SSPD, SNSPD  
  Abstract (up) We present a novel, two-channel, single photon receiver based on two fibre-coupled, NbN, superconducting, single photon detectors (SSPDs). The SSPDs are nanostructured superconducting meanders and are known for ultrafast and efficient detection of visible-to-infrared photons. Coupling between the NbN detector and optical fibre was achieved using a micromechanical photoresist ring placed directly over the SSPD, holding the fibre in place. With this arrangement, we obtained coupling efficiencies up to ∼30%. Our experimental results showed that the best receiver had a near-infrared system quantum efficiency of 0.33% at 4.2 K. The quantum efficiency increased exponentially with the photon energy increase, reaching a few percent level for visible-light photons. The photoresponse pulses of our devices were limited by the meander high kinetic inductance and had the rise and fall times of approximately 250 ps and 5 ns, respectively. The receiver's timing jitter was in the 37 to 58 ps range, approximately 2 to 3 times larger than in our older free-space-coupled SSPDs. We stipulate that this timing jitter is in part due to optical fibre properties. Besides quantum communications, the two-detector arrangement should also find applications in quantum correlation experiments.  
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  Series Volume Series Issue Edition  
  ISSN 0950-0340 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1434  
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Author Gol'tsman, G.; Minaeva, O.; Korneev, A.; Tarkhov, M.; Rubtsova, I.; Divochiy, A.; Milostnaya, I.; Chulkova, G.; Kaurova, N.; Voronov, B.; Pan, D.; Kitaygorsky, J.; Cross, A.; Pearlman, A.; Komissarov, I.; Slysz, W.; Wegrzecki, M.; Grabiec, P.; Sobolewski, R. url  doi
openurl 
  Title Middle-infrared to visible-light ultrafast superconducting single-photon detectors Type Journal Article
  Year 2007 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.  
  Volume 17 Issue 2 Pages 246-251  
  Keywords SSPD, SNSPD  
  Abstract (up) We present an overview of the state-of-the-art of NbN superconducting single-photon detectors (SSPDs). Our devices exhibit quantum efficiency (QE) of up to 30% in near-infrared wavelength and 0.4% at 5 mum, with a dark-count rate that can be as low as 10 -4 s -1 . The SSPD structures integrated with lambda/4 microcavities achieve a QE of 60% at telecommunication, 1550-nm wavelength. We have also developed a new generation of SSPDs that possess the QE of large-active-area devices, but, simultaneously, are characterized by low kinetic inductance that allows achieving short response times and the GHz-counting rate with picosecond timing jitter. The improvements presented in the SSPD development, such as fiber-coupled SSPDs, make our detectors most attractive for high-speed quantum communications and quantum computing.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1051-8223 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 431  
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