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Author Korneev, A. A.; Korneeva, Y. P.; Mikhailov, M. Yu.; Pershin, Y. P.; Semenov, A. V.; Vodolazov, D. Yu.; Divochiy, A. V.; Vakhtomin, Y. B.; Smirnov, K. V.; Sivakov, A. G.; Devizenko, A. Yu.; Goltsman, G. N.
Title Characterization of MoSi superconducting single-photon detectors in the magnetic field Type Journal Article
Year 2015 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume (down) 25 Issue 3 Pages 2200504 (1 to 4)
Keywords SSPD, SNSPD
Abstract We investigate the response mechanism of nanowire superconducting single-photon detectors (SSPDs) made of amorphous MoxSi1-x. We study the dependence of photon count and dark count rates on bias current in magnetic fields up to 113 mT at 1.7 K temperature. The observed behavior of photon counts is similar to the one recently observed in NbN SSPDs. Our results show that the detecting mechanism of relatively high-energy photons does not involve the vortex penetration from the edges of the film, and on the contrary, the detecting mechanism of low-energy photons probably involves the vortex penetration from the film edges.
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Call Number RPLAB @ akorneev @ KorneevIEEE2015 Serial 991
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Author Kardakova, A. I.; Coumou, P. C. J. J.; Finkel, M. I.; Morozov, D. V.; An, P. P.; Goltsman, G. N.; Klapwijk, T. M.
Title Electron–phonon energy relaxation time in thin strongly disordered titanium nitride films Type Journal Article
Year 2015 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume (down) 25 Issue 3 Pages 1-4
Keywords TiN MKID
Abstract We have measured the energy relaxation times from the electron bath to the phonon bath in strongly disordered TiN films grown by atomic layer deposition. The measured values of τ eph vary from 12 to 91 ns. Over a temperature range from 3.4 to 1.7 K, they follow T -3 temperature dependence, which are consistent with values of τ eph reported previously for sputtered TiN films. For the most disordered film, with an effective elastic mean free path of 0.35 nm, we find a faster relaxation and a stronger temperature dependence, which may be an additional indication of the influence of strong disorder on a superconductor.
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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 1296
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Author Tong, C.-Y. E.; Trifonov, A.; Shurakov, A.; Blundell, R.; Gol’tsman, G.
Title A microwave-operated hot-electron-bolometric power detector for terahertz radiation Type Journal Article
Year 2015 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume (down) 25 Issue 3 Pages 2300604 (1 to 4)
Keywords NbN HEB mixer
Abstract A new class of microwave-operated THz power detectors based on the NbN hot-electron-bolometer (HEB) mixer is proposed. The injected microwave signal ( 1 GHz) serves the dual purpose of pumping the HEB element and enabling the read-out of the internal state of the device. A cryogenic amplifier amplifies the reflected microwave signal from the device and a homodyne scheme recovers the effects of the incident THz radiation. Two modes of operation have been identified, depending on the level of incident radiation. For weak signals, we use a chopper to chop the incident radiation against a black body reference and a lock-in amplifier to perform synchronous detection of the homodyne readout. The voltage measured is proportional to the incident power, and we estimate an optical noise equivalent power of  5pW/ √Hz at 0.83 THz. At higher signal levels, the homodyne circuit recovers the stream of steady relaxation oscillation pulses from the HEB device. The frequency of these pulses is in the MHz frequency range and bears a linear relationship with the incident THz radiation over an input power range of  15 dB. A digital frequency counter is used to measure THz power. The applicable power range is between 1 nW and 1 μW.
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Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1558-2515 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 1354
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Author Yang, Y.; Fedorov, G.; Shafranjuk, S. E.; Klapwijk, T. M.; Cooper, B. K.; Lewis, R. M.; Lobb, C. J.; Barbara, P.
Title Electronic transport and possible superconductivity at Van Hove singularities in carbon nanotubes Type Journal Article
Year 2015 Publication Nano Lett. Abbreviated Journal Nano Lett.
Volume (down) 15 Issue 12 Pages 7859-7866
Keywords carbon nanotubes, CNT, tunable superconductivity, van Hove singularities
Abstract Van Hove singularities (VHSs) are a hallmark of reduced dimensionality, leading to a divergent density of states in one and two dimensions and predictions of new electronic properties when the Fermi energy is close to these divergences. In carbon nanotubes, VHSs mark the onset of new subbands. They are elusive in standard electronic transport characterization measurements because they do not typically appear as notable features and therefore their effect on the nanotube conductance is largely unexplored. Here we report conductance measurements of carbon nanotubes where VHSs are clearly revealed by interference patterns of the electronic wave functions, showing both a sharp increase of quantum capacitance, and a sharp reduction of energy level spacing, consistent with an upsurge of density of states. At VHSs, we also measure an anomalous increase of conductance below a temperature of about 30 K. We argue that this transport feature is consistent with the formation of Cooper pairs in the nanotube.
Address Department of Physics, Georgetown University , Washington, District of Columbia 20057, United States
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ISSN 1530-6984 ISBN Medium
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Notes PMID:26506109; Suuplementary info (attached to pdf) DOI: 10.1021/acs.nanolett.5b02564 Approved no
Call Number Serial 1782
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Author Sidorova, Maria V.; Divochiy, Alexander V.; Vakhtomin, Yury B.; Smirnov, Konstantin V.
Title Ultrafast superconducting single-photon detector with a reduced active area coupled to a tapered lensed single-mode fiber Type Journal Article
Year 2015 Publication J. Nanophoton. Abbreviated Journal
Volume (down) 9 Issue 1 Pages 093051
Keywords SSPD, SNSPD
Abstract This paper presents an ultrafast niobium nitride (NbN) superconducting single-photon detector (SSPD) with an active area of 3×3  μm2 that offers better timing performance metrics than the previous SSPD with an active area of 7×7  μm2. The improved SSPD demonstrates a record timing jitter (<25  ps), an ultrashort recovery time (<2  ns), an extremely low dark count rate, and a high detection efficiency in a wide spectral range from visible part to near infrared. The record parameters were obtained due to the development of a new technique providing effective optical coupling between a detector with a reduced active area and a standard single-mode telecommunication fiber. The advantages of the new approach are experimentally confirmed by taking electro-optical measurements.
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ISSN 1934-2608 ISBN Medium
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Notes 10.1117/1.JNP.9.093051 Approved no
Call Number RPLAB @ sasha @ Serial 1052
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Author Smirnov, Konstantin; Vachtomin, Yury; Divochiy, Alexander; Antipov, Andrey; Goltsman, Gregory
Title Dependence of dark count rates in superconducting single photon detectors on the filtering effect of standard single mode optical fibers Type Journal Article
Year 2015 Publication Appl. Phys. Express Abbreviated Journal Appl. Phys. Express
Volume (down) 8 Issue 2 Pages 022501 (1 to 4)
Keywords
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Corporate Author Thesis
Publisher IOP Publishing Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
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ISSN 1882-0778 ISBN Medium
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Notes Approved no
Call Number RPLAB @ sasha @ smirnov2015dependence Serial 1049
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Author Kahl, O.; Ferrari, S.; Kovalyuk, V.; Goltsman, G. N.; Korneev, A.; Pernice, W. H. P.
Title Waveguide integrated superconducting single-photon detectors with high internal quantum efficiency at telecom wavelengths Type Journal Article
Year 2015 Publication Sci. Rep. Abbreviated Journal Sci. Rep.
Volume (down) 5 Issue Pages 10941 (1 to 11)
Keywords optical waveguides; waveguide integrated SSPD; waveguide SSPD; nanophotonics
Abstract Superconducting nanowire single-photon detectors (SNSPDs) provide high efficiency for detecting individual photons while keeping dark counts and timing jitter minimal. Besides superior detection performance over a broad optical bandwidth, compatibility with an integrated optical platform is a crucial requirement for applications in emerging quantum photonic technologies. Here we present efficiencies close to unity at 1550nm wavelength. This allows for the SNSPDs to be operated at bias currents far below the critical current where unwanted dark count events reach milli-Hz levels while on-chip detection efficiencies above 70% are maintained. The measured dark count rates correspond to noiseequivalent powers in the 10–19W/Hz–1/2 range and the timing jitter is as low as 35ps. Our detectors are fully scalable and interface directly with waveguide-based optical platforms.
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Notes PMID:26061283; PMCID:PMC4462017 Approved no
Call Number RPLAB @ kovalyuk @ Serial 946
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Author Shurakov, A.; Tong, Cheuk-yu E.; Grimes, P.; Blundell, R.; Golt'sman, G.
Title A microwave reflection readout scheme for hot electron bolometric direct detector Type Journal Article
Year 2015 Publication IEEE Trans. THz Sci. Technol. Abbreviated Journal IEEE Trans. THz Sci. Technol.
Volume (down) 5 Issue Pages 81-84
Keywords HEB detectors
Abstract In this paper, we propose and present data from a fast THz detector based on the repurpose of hot electron bolometer mixers (HEB) fabricated from superconducting NbN thinfilm. This detector is essentially a traditional NbN bolometer element that operates under the influence of a microwave pump. The in-jected microwave power serves the dual purpose of enhancing the detector sensitivity and reading out the impedance changes of the device in response to incidentTHz radiation. We have measured an optical Noise Equivalent Power of 4 pW/ Hz for our detector at a bath temperature of 4.2 K. The measurement frequency was 0.83 THz and the modulation frequency was 1.48 kHz. The readout

scheme is versatile and facilitates both high-speed operation as well as multi-pixel applications.
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Notes Approved no
Call Number RPLAB @ atomics90 @ Serial 950
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Author Murphy, A.; Semenov, A.; Korneev, A.; Korneeva, Y.; Gol'tsman, G.; Bezryadin, A.
Title Three temperature regimes in superconducting photon detectors: quantum, thermal and multiple phase-slips as generators of dark counts Type Journal Article
Year 2015 Publication Sci. Rep. Abbreviated Journal Sci. Rep.
Volume (down) 5 Issue Pages 10174 (1 to 10)
Keywords SPD, SSPD, SNSPD
Abstract We perform measurements of the switching current distributions of three w approximately 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter of the vortex cores, so they are classified as quasi-two-dimensional (quasi-2D). We discover evidence of macroscopic quantum tunneling by observing the saturation of the standard deviation of the switching distributions at temperatures around 2 K. We analyze our results using the Kurkijarvi-Garg model and find that the escape temperature also saturates at low temperatures, confirming that at sufficiently low temperatures, macroscopic quantum tunneling is possible in quasi-2D strips and can contribute to dark counts observed in single photon detectors. At the highest temperatures the system enters a multiple phase-slip regime. In this range single phase-slips are unable to produce dark counts and the fluctuations in the switching current are reduced.
Address Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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ISSN 2045-2322 ISBN Medium
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Notes PMID:25988591; PMCID:PMC4437302 Approved no
Call Number Serial 1344
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Author Takemoto, K.; Nambu, Y.; Miyazawa, T.; Sakuma, Y.; Yamamoto, T.; Yorozu, S.; Arakawa, Y.
Title Quantum key distribution over 120 km using ultrahigh purity single-photon source and superconducting single-photon detectors Type Journal Article
Year 2015 Publication Sci. Rep. Abbreviated Journal
Volume (down) 5 Issue Pages 14383
Keywords SSPD, SNSPD applications, quantum key distribution, QKD
Abstract Advances in single-photon sources (SPSs) and single-photon detectors (SPDs) promise unique applications in the field of quantum information technology. In this paper, we report long-distance quantum key distribution (QKD) by using state-of-the-art devices: a quantum-dot SPS (QD SPS) emitting a photon in the telecom band of 1.5 μm and a superconducting nanowire SPD (SNSPD). At the distance of 100 km, we obtained the maximal secure key rate of 27.6 bps without using decoy states, which is at least threefold larger than the rate obtained in the previously reported 50-km-long QKD experiment. We also succeeded in transmitting secure keys at the rate of 0.307 bps over 120 km. This is the longest QKD distance yet reported by using known true SPSs. The ultralow multiphoton emissions of our SPS and ultralow dark count of the SNSPD contributed to this result. The experimental results demonstrate the potential applicability of QD SPSs to practical telecom QKD networks.
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Notes Approved no
Call Number Serial 1104
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