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Minaeva, O., Divochiy, A., Korneev, A., Sergienko, A. V., & Goltsman, G. N. (2009). High speed infrared photon counting with photon number resolving superconducting single-photon detectors (SSPDs). In CLEO/Europe – EQEC.
Abstract: A review of development and characterization of the nanostructures consisting of several meander sections, all connected in parallel was presented. Such geometry leads to a significant decrease of the kinetic inductance, without a decrease of the SSPD active area. A new type of SSPDs possess the QE of large-active- area devices, but, simultaneously, allows achieving short response times and the GHz-counting rate. This new generation of superconducting detectors has another significant advantage for quantum key distribution, they have a photon number resolving capability and can distinguish more photons.
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Ryabchun, S., Tong, C. - Y. E., Blundell, R., & Gol'tsman, G. (2009). Stabilization scheme for hot-electron bolometer receivers using microwave radiation. IEEE Trans. Appl. Supercond., 19(1), 14–19.
Abstract: We present the results of a stabilization scheme for terahertz receivers based on NbN hot-electron bolometer (HEB) mixers that uses microwave radiation with a frequency much lower than the gap frequency of NbN to compensate for mixer current fluctuations. A feedback control loop, which actively controls the power level of the injected microwave radiation, has successfully been implemented to stabilize the operating point of the HEB mixer. This allows us to increase the receiver Allan time to 10 s and also improve the temperature resolution of the receiver by about 30% in the total power mode of operation.
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Ryabchun, S., Tong, C. - Y. E., Paine, S., Lobanov, Y., Blundell, R., & Goltsman, G. (2009). Temperature resolution of an HEB receiver at 810 GHz. IEEE Trans. Appl. Supercond., 19(3), 293–296.
Abstract: We present the results of direct measurements of the temperature resolution of an HEB receiver operating at 810 GHz, in both continuum and spectroscopic modes. In the continuum mode, the input of the receiver was switched between black bodies with different physical temperatures. With a system noise temperature of around 1100 K, the receiver was able to resolve loads which differed in temperature by about 1 K over an integration time of 5 seconds. This resolution is significantly worse than the value of 0.07 K given by the radiometer equation. In the spectroscopic mode, a gas cell filled with carbonyl sulphide (OCS) gas was used and the emission line at 813.3537060 GHz was measured using the receiver in conjunction with a digital spectrometer. From the observed spectra, we determined that the measurement uncertainty of the equivalent emission temperature was 2.8 K for an integration time of 0.25 seconds and a spectral resolution of 12 MHz, compared to a 1.4 K temperature resolution given by the radiometer equation. This relative improvement is due to the fact that at short integration times the contribution from 1/f noise and drift are less dominant. In both modes, the temperature resolution was improved by about 40% with the use of a feedback loop which adjusted the level of an injected microwave radiation to maintain a constant operating current of the HEB mixer. This stabilization scheme has proved to be very effective to keep the temperature resolution of the HEB receiver to close to the theoretical value given by the radiometer equation.
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Meledin, D., Pavolotsky, A., Desmaris, V., Lapkin, I., Risacher, C., Perez, V., et al. (2009). A 1.3-THz balanced waveguide HEB mixer for the APEX telescope. IEEE Trans. Microw. Theory Techn., 57(1), 89–98.
Abstract: In this paper, we report about the development, fabrication, and characterization of a balanced waveguide hot electron bolometer (HEB) receiver for the Atacama Pathfinder EXperiment telescope covering the frequency band of 1.25–1.39 THz. The receiver uses a quadrature balanced scheme and two HEB mixers, fabricated from 4- to 5-nm-thick NbN film deposited on crystalline quartz substrate with an MgO buffer layer in between. We employed a novel micromachining method to produce all-metal waveguide parts at submicrometer accuracy (the main-mode waveguide dimensions are 90×180 μm). We present details on the mixer design and measurement results, including receiver noise performance, stability and “first-light†at the telescope site. The receiver yields a double-sideband noise temperature averaged over the RF band below 1200 K, and outstanding stability with a spectroscopic Allan time more than 200 s.
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Goltsman, G. N. (2009). Ultrafast nanowire superconducting single-photon detector with photon number resolving capability. In Y. Arakawa, M. Sasaki, & H. Sotobayashi (Eds.), Proc. SPIE (Vol. 7236, 72360D (1 to 11)). SPIE.
Abstract: In this paper we present a review of the state-of-the-art superconducting single-photon detector (SSPD), its characterization and applications. We also present here the next step in the development of SSPD, i.e. photon-number resolving SSPD which simultaneously features GHz counting rate. We have demonstrated resolution up to 4 photons with quantum efficiency of 2.5% and 300 ps response pulse duration providing very short dead time.
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