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Korneev, A. A., Korneeva, Y. P., Mikhailov, M. Y., Pershin, Y. P., Semenov, A. V., Vodolazov, D. Y., et al. (2015). Characterization of MoSi superconducting single-photon detectors in the magnetic field. IEEE Trans. Appl. Supercond., 25(3), 2200504 (1 to 4).
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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Kardakova, A. I., Coumou, P. C. J. J., Finkel, M. I., Morozov, D. V., An, P. P., Goltsman, G. N., et al. (2015). Electron–phonon energy relaxation time in thin strongly disordered titanium nitride films. IEEE Trans. Appl. Supercond., 25(3), 1–4.
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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Tong, C. - Y. E., Trifonov, A., Shurakov, A., Blundell, R., & Gol’tsman, G. (2015). A microwave-operated hot-electron-bolometric power detector for terahertz radiation. IEEE Trans. Appl. Supercond., 25(3), 2300604 (1 to 4).
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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Shurakov, A., Tong, C. -yu E., Grimes, P., Blundell, R., & Golt'sman, G. (2015). A microwave reflection readout scheme for hot electron bolometric direct detector. IEEE Trans. THz Sci. Technol., 5, 81–84.
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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Mehdi, I., Gol'tsman, G., & Putz, P. (2015). Introduction to the mini-special-issue on the 25th international symposium on space terahertz technology (ISSTT) (Vol. 5).
Abstract: THE 25th International Symposium on Space Terahertz Technology (ISSTT) was held in Moscow, Russia, between April 27–30, 2014. The conference was organized by Moscow State Pedagogical University and the Higher School of Economics (National Research University) and Chaired by Professor Gregory Gol'tsman of Moscow State Pedagogical University. The conference was attended by roughly 150 participants from 15 countries. The technology covered by ISSTT includes detectors, devices, circuits and systems in various areas of THz science and technology. Each year this symposium brings together the global THz space science technology community, and as such, emphasizes the broad international collaboration that is required to execute these large complicated instrument programs that dominate this field. However, talks covering technologies for balloon, aircraft, and ground-based telescopes were also presented.
In this special section of IEEE Transactions on Terahertz Science and Technology, we include eight expanded papers from the 25th ISSTT symposium. The papers range from development of SIS mixers to optical adjustment systems for radio telescopes. The 26th ISSTT will be held in Boston, MA, USA, during March 16–18, 2015. Researchers and scientist involved in THz research are invited to attend this symposium (more details are at http://www.cfa.harvard.edu/events/2015/isstt2015/).
You can access the full list of papers presented at the ISSTT symposia from the National Radio Astronomy Observatory website: http://www.nrao.edu/meetings/isstt/index.shtml
Yours sincerely
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Gayduchenko, I., Kardakova, A., Fedorov, G., Voronov, B., Finkel, M., Jiménez, D., et al. (2015). Response of asymmetric carbon nanotube network devices to sub-terahertz and terahertz radiation. J. Appl. Phys., 118(19), 194303.
Abstract: Demand for efficient terahertz radiation detectors resulted in intensive study of the asymmetric carbon nanostructures as a possible solution for that problem. It was maintained that photothermoelectric effect under certain conditions results in strong response of such devices to terahertz radiation even at room temperature. In this work, we investigate different mechanisms underlying the response of asymmetric carbon nanotube (CNT) based devices to sub-terahertz and terahertz radiation. Our structures are formed with CNT networks instead of individual CNTs so that effects probed are more generic and not caused by peculiarities of an individual nanoscale object. We conclude that the DC voltage response observed in our structures is not only thermal in origin. So called diode-type response caused by asymmetry of the device IV characteristic turns out to be dominant at room temperature. Quantitative analysis provides further routes for the optimization of the device configuration, which may result in appearance of novel terahertz radiation detectors.
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Korneev, A., Golt'sman, G., & Pernice, W. (2015). Photonic integration meets single-photon detection (Vol. 51).
Abstract: By embedding superconducting nanowire single-photon detectors (SNSPDs) in nanophotonic circuits, these waveguide-integrated detectors are a key building block for future on-chip quantum computing applications.
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Yang, Y., Fedorov, G., Shafranjuk, S. E., Klapwijk, T. M., Cooper, B. K., Lewis, R. M., et al. (2015). Electronic transport and possible superconductivity at Van Hove singularities in carbon nanotubes. Nano Lett., 15(12), 7859–7866.
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.
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Takesue, H., Dyer, S. D., Stevens, M. J., Verma, V., Mirin, R. P., & Nam, S. W. (2015). Quantum teleportation over 100 km of fiber using highly efficient superconducting nanowire single-photon detectors. Optica, 2.
Abstract: Quantum teleportation is an essential quantum operation by which we can transfer an unknown quantum state to a remote location with the help of quantum entanglement and classical communication. Since the first experimental demonstrations using photonic qubits and continuous variables, the distance of photonic quantum teleportation over free-space channels has continued to increase and has reached >100 km. On the other hand, quantum teleportation over optical fiber has been challenging, mainly because the multifold photon detection that inevitably accompanies quantum teleportation experi- ments has been very inefficient due to the relatively low de- tection efficiencies of typical telecom-band single-photon detectors. Here, we report on quantum teleportation over optical fiber using four high-detection-efficiency supercon- ducting nanowire single-photon detectors (SNSPDs). These SNSPDs make it possible to perform highly efficient multi- fold photon measurements, allowing us to confirm that the quantum states of input photons were successfully tele- ported over 100 km of fiber with an average fidelity of 83.7 2.0%.
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Kozorezov, A. G., Lambert, C., Marsili, F., Stevens, M. J., Verma, V. B., Stern, J. A., et al. (2015). Quasiparticle recombination in hotspots in superconducting current-carrying nanowires. Phys. Rev. B, 92(6).
Abstract: We describe a kinetic model of recombination of non-equilibrium quasiparticles generated by single photon absorption in superconducting current-carrying nanowires. The model is developed to interpret two-photon detection experiments in which a single photon does not possess sufficient energy for breaking superconductivity at a fixed low bias current. We show that quasiparticle self- recombination in relaxing hotspot dominates diffusion expansion effects and explains the observed strong bias current, wavelength and temperature dependencies of hotspot relaxation in tungsten silicide superconducting nanowire single-photon detectors.
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