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Manova, N. N., Simonov, N. O., Korneeva, Y. P., & Korneev, A. A. (2020). Developing of NbN films for superconducting microstrip single-photon detector. In J. Phys.: Conf. Ser. (Vol. 1695, 012116 (1 to 5)).
Abstract: We optimized NbN films on a Si substrate with a buffer SiO2 layer to produce superconducting microstrip single-photon detectors with saturated dependence of quantum efficiency (QE) versus normalized bias current. We varied thickness of films and observed the maximum QE saturation for device based on the thinner film with the lowest ratio RS300/RS20.
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Polyakova, M. I., Korneev, A. A., & Semenov, A. V. (2020). Comparison single- and double- spot detection efficiencies of SSPD based to MoSi and NbN films. In J. Phys.: Conf. Ser. (Vol. 1695, 012146 (1 to 3)).
Abstract: In this work, we present results of quantum detector tomography of superconducting single photon detector (SSPD) based on MoSi film, and compare them with previously reported data on NbN. We find that for both materials hot spot interaction length coincides with the strip width, and the dependence of single and double-spot detection efficiencies on bias current are compatible with sufficiently large hot-spot size, approaching the strip width.
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Baeva, E., Sidorova, M., Korneev, A., & Goltsman, G. (2018). Precise measurement of the thermal conductivity of superconductor. In Proc. AIP Conf. (Vol. 1936, 020003 (1 to 4)).
Abstract: Measuring the thermal properties such as the heat capacity provide information about intrinsic mechanisms operated inside. In general, the ratio between electron and phonon specific heat Ce/Cp shows how the absorbed energy shared between electron and phonon subsystems. In this work we make estimations for amplitude-modulated absorption of THz radiation technique for investigation of the ratio Ce/Cp in superconducting Niobium Nitride (NbN) at T = Tc. Our results indicates that experimentally the frequency of modulation has to be extra large to extract the quantity. We perform a new technique allowed to work at low frequency with accurately measurement of absorbed power.
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Verevkin, A. A., Zhang, J., Slysz, W., Sobolewski, R., Lipatov, A. P., Okunev, O., et al. (2002). Superconducting single-photon detectors for GHz-rate free-space quantum communications. In J. C. Ricklin, & D. G. Voelz (Eds.), Proc. SPIE (Vol. 4821, pp. 447–454). SPIE.
Abstract: We report our studies on the performance of new NbN ultrathin-film superconducting single-photon detectors (SSPDs). Our SSPDs exhibit experimentally measured quantum efficiencies from 5% at wavelength λ = 1550 nm up to 10% at λ = 405 nm, with exponential, activation-energy-type spectral sensitivity dependence in the 0.4-μm – 3-μm wavelength range. Using a variable optical delay setup, we have shown that our NbN SSPDs can resolve optical photons with a counting rate up to 10 GHz, presently limited by the read-out electronics. The measured device jitter was below 35 ps under optimum biasing conditions. The extremely high photon counting rate, together with relatively high (especially for λ > 1 μm) quantum efficiency, low jitter, and very low dark counts, make NbN SSPDs very promising for free-space communications and quantum cryptography.
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Verevkin, A. A., Pearlman, A., Slysz, W., Zhang, J., Sobolewski, R., Chulkova, G., et al. (2003). Ultrafast superconducting single-photon detectors for infrared wavelength quantum communications. In E. Donkor, A. R. Pirich, & H. E. Brandt (Eds.), Proc. SPIE (Vol. 5105, pp. 160–170). SPIE.
Abstract: We have developed a new class of superconducting single-photon detectors (SSPDs) for ultrafast counting of infrared (IR) photons for secure quantum communications. The devices are operated on the quantum detection mechanism, based on the photon-induced hotspot formation and subsequent appearance of a transient resistive barrier across an ultrathin and submicron-wide superconducting stripe. The detectors are fabricated from 3.5-nm-thick NbN films and they operate at 4.2 K inside a closed-cycle refrigerator or liquid helium cryostat. Various continuous and pulsed laser sources have been used in our experiments, enabling us to determine the detector experimental quantum efficiency (QE) in the photon-counting mode, response time, time jitter, and dark counts. Our 3.5-nm-thick SSPDs reached QE above 15% for visible light photons and 5% at 1.3 – 1.5 μm infrared range. The measured real-time counting rate was above 2 GHz and was limited by the read-out electronics (intrinsic response time is <30 ps). The measured jitter was <18 ps, and the dark counting rate was <0.01 per second. The measured noise equivalent power (NEP) is 2 x 10-18 W/Hz1/2 at λ = 1.3 μm. In near-infrared range, in terms of the counting rate, jitter, dark counts, and overall sensitivity, the NbN SSPDs significantly outperform their semiconductor counterparts. An ultrafast quantum cryptography communication technology based on SSPDs is proposed and discussed.
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