Glejm, A. V., Anisimov, A. A., Asnis, L. N., Vakhtomin, Y. B., Divochiy, A. V., Egorov, V. I., et al. (2014). Quantum key distribution in an optical fiber at distances of up to 200 km and a bit rate of 180 bit/s. Bulletin of the Russian Academy of Sciences. Physics, 78(3), 171–175.
Abstract: An experimental demonstration of a subcarrier-wave quantum cryptography system with superconducting single-photon detectors (SSPDs) that distributes a secure key in a single-mode fiber at distance of 25 km with a bit rate of 800 kbit/s, a distance of 100 km with a bit rate of 19 kbit/s, and a distance of 200 km with a bit rate of 0.18 kbit/s is described.
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Kardakova, A., Finkel, M., Morozov, D., Kovalyuk, V., An, P., Dunscombe, C., et al. (2013). The electron-phonon relaxation time in thin superconducting titanium nitride films. Appl. Phys. Lett., 103(25), 252602 (1 to 4).
Abstract: We report on the direct measurement of the electron-phonon relaxation time, τeph, in disordered TiN films. Measured values of τeph are from 5.5 ns to 88 ns in the 4.2 to 1.7 K temperature range and consistent with a T−3 temperature dependence. The electronic density of states at the Fermi level N0 is estimated from measured material parameters. The presented results confirm that thin TiN films are promising candidate-materials for ultrasensitive superconducting detectors.
The work was supported by the Ministry of Education and Science of the Russian Federation, Contract No. 14.B25.31.0007 and by the RFBR Grant No. 13-02-91159.
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Kahl, O., Ferrari, S., Kovalyuk, V., Goltsman, G. N., Korneev, A., & Pernice, W. H. P. (2015). Waveguide integrated superconducting single-photon detectors with high internal quantum efficiency at telecom wavelengths. Sci. Rep., 5, 10941 (1 to 11).
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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Ozhegov, R., Elezov, M., Kurochkin, Y., Kurochkin, V., Divochiy, A., Kovalyuk, V., et al. (2014). Quantum key distribution over 300. In A. A. Orlikovsky (Ed.), Proc. SPIE (Vol. 9440, 1F (1 to 9)). SPIE.
Abstract: We discuss the possibility of polarization state reconstruction and measurement over 302 km by Superconducting Single- Photon Detectors (SSPDs). Because of the excellent characteristics and the possibility to be effectively coupled to singlemode optical fiber many applications of the SSPD have already been reported. The most impressive one is the quantum key distribution (QKD) over 250 km distance. This demonstration shows further possibilities for the improvement of the characteristics of quantum-cryptographic systems such as increasing the bit rate and the quantum channel length, and decreasing the quantum bit error rate (QBER). This improvement is possible because SSPDs have the best characteristics in comparison with other single-photon detectors. We have demonstrated the possibility of polarization state reconstruction and measurement over 302.5 km with superconducting single-photon detectors. The advantage of an autocompensating optical scheme, also known as “plugandplay” for quantum key distribution, is high stability in the presence of distortions along the line. To increase the distance of quantum key distribution with this optical scheme we implement the superconducting single photon detectors (SSPD). At the 5 MHz pulse repetition frequency and the average photon number equal to 0.4 we measured a 33 bit/s quantum key generation for a 101.7 km single mode ber quantum channel. The extremely low SSPD dark count rate allowed us to keep QBER at 1.6% level.
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Khasminskaya, S., Pyatkov, F., Słowik, K., Ferrari, S., Kahl, O., Kovalyuk, V., et al. (2016). Fully integrated quantum photonic circuit with an electrically driven light source. Nat. Photon., 10(11), 727–732.
Abstract: Photonic quantum technologies allow quantum phenomena to be exploited in applications such as quantum cryptography, quantum simulation and quantum computation. A key requirement for practical devices is the scalable integration of single-photon sources, detectors and linear optical elements on a common platform. Nanophotonic circuits enable the realization of complex linear optical systems, while non-classical light can be measured with waveguide-integrated detectors. However, reproducible single-photon sources with high brightness and compatibility with photonic devices remain elusive for fully integrated systems. Here, we report the observation of antibunching in the light emitted from an electrically driven carbon nanotube embedded within a photonic quantum circuit. Non-classical light generated on chip is recorded under cryogenic conditions with waveguide-integrated superconducting single-photon detectors, without requiring optical filtering. Because exclusively scalable fabrication and deposition methods are used, our results establish carbon nanotubes as promising nanoscale single-photon emitters for hybrid quantum photonic devices.
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Pyatkov, F., Khasminskaya, S., Kovalyuk, V., Hennrich, F., Kappes, M. M., Goltsman, G. N., et al. (2017). Sub-nanosecond light-pulse generation with waveguide-coupled carbon nanotube transducers. Beilstein J. Nanotechnol., 8, 38–44.
Abstract: Carbon nanotubes (CNTs) have recently been integrated into optical waveguides and operated as electrically-driven light emitters under constant electrical bias. Such devices are of interest for the conversion of fast electrical signals into optical ones within a nanophotonic circuit. Here, we demonstrate that waveguide-integrated single-walled CNTs are promising high-speed transducers for light-pulse generation in the gigahertz range. Using a scalable fabrication approach we realize hybrid CNT-based nanophotonic devices, which generate optical pulse trains in the range from 200 kHz to 2 GHz with decay times below 80 ps. Our results illustrate the potential of CNTs for hybrid optoelectronic systems and nanoscale on-chip light sources.
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Ferrari, S., Kovalyuk, V., Hartmann, W., Vetter, A., Kahl, O., Lee, C., et al. (2017). Hot-spot relaxation time current dependence in niobium nitride waveguide-integrated superconducting nanowire single-photon detectors. Opt. Express, 25(8), 8739–8750.
Abstract: We investigate how the bias current affects the hot-spot relaxation dynamics in niobium nitride. We use for this purpose a near-infrared pump-probe technique on a waveguide-integrated superconducting nanowire single-photon detector driven in the two-photon regime. We observe a strong increase in the picosecond relaxation time for higher bias currents. A minimum relaxation time of (22 +/- 1)ps is obtained when applying a bias current of 50% of the switching current at 1.7 K bath temperature. We also propose a practical approach to accurately estimate the photon detection regimes based on the reconstruction of the measured detector tomography at different bias currents and for different illumination conditions.
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Kahl, O., Ferrari, S., Kovalyuk, V., Vetter, A., Lewes-Malandrakis, G., Nebel, C., et al. (2017). Spectrally multiplexed single-photon detection with hybrid superconducting nanophotonic circuits. Optica, 4(5), 557–562.
Abstract: The detection of individual photons by superconducting nanowire single-photon detectors is an inherently binary mechanism, revealing either their absence or presence while concealing their spectral information. For multicolor imaging techniques, such as single-photon spectroscopy, fluorescence resonance energy transfer microscopy, and fluorescence correlation spectroscopy, wavelength discrimination is essential and mandates spectral separation prior to detection. Here, we adopt an approach borrowed from quantum photonic integration to realize a compact and scalable waveguide-integrated single-photon spectrometer capable of parallel detection on multiple wavelength channels, with temporal resolution below 50 ps and dark count rates below 10 Hz at 80% of the devices' critical current. We demonstrate multidetector devices for telecommunication and visible wavelengths, and showcase their performance by imaging silicon vacancy color centers in diamond nanoclusters. The fully integrated hybrid superconducting nanophotonic circuits enable simultaneous spectroscopy and lifetime mapping for correlative imaging and provide the ingredients for quantum wavelength-division multiplexing on a chip.
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Kovalyuk, V., Ferrari, S., Kahl, O., Semenov, A., Shcherbatenko, M., Lobanov, Y., et al. (2017). On-chip coherent detection with quantum limited sensitivity. Sci Rep, 7(1), 4812.
Abstract: While single photon detectors provide superior intensity sensitivity, spectral resolution is usually lost after the detection event. Yet for applications in low signal infrared spectroscopy recovering information about the photon's frequency contributions is essential. Here we use highly efficient waveguide integrated superconducting single-photon detectors for on-chip coherent detection. In a single nanophotonic device, we demonstrate both single-photon counting with up to 86% on-chip detection efficiency, as well as heterodyne coherent detection with spectral resolution f/f exceeding 10(11). By mixing a local oscillator with the single photon signal field, we observe frequency modulation at the intermediate frequency with ultra-low local oscillator power in the femto-Watt range. By optimizing the nanowire geometry and the working parameters of the detection scheme, we reach quantum-limited sensitivity. Our approach enables to realize matrix integrated heterodyne nanophotonic devices in the C-band wavelength range, for classical and quantum optics applications where single-photon counting as well as high spectral resolution are required simultaneously.
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Kovalyuk, V., Ferrari, S., Kahl, O., Semenov, A., Lobanov, Y., Shcherbatenko, M., et al. (2017). Waveguide integrated superconducting single-photon detector for on-chip quantum and spectral photonic application. In J. Phys.: Conf. Ser. (Vol. 917, 062032).
Abstract: With use of the travelling-wave geometry approach, integrated superconductor- nanophotonic devices based on silicon nitride nanophotonic waveguide with a superconducting NbN-nanowire suited on top of the waveguide were fabricated. NbN-nanowire was operated as a single-photon counting detector with up to 92 % on-chip detection efficiency in the coherent mode, serving as a highly sensitive IR heterodyne mixer with spectral resolution (f/df) greater than 106 in C-band at 1550 nm wavelength
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