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with the photon signal input. So, it was conrmed that a multi-pixel SSPD operates in combination with an SFQ encoder [24]. In the future, we plan to verify real-time imaging operation including signal processing at room temperature and continue to develop larger pixel detectors [25] by making the best use of SFQ signal processing of NICT, taking the method of a readout signal with 2N outputs from an N × N pixel SSPD that the National Institute of Standards and Technology (NIST) group pro-poses [26].e ultimate goal of SFQ signal processing is mono-lithic integration with a multi-pixel SSPD. We have already started to develop monolithic integration of a 16-pixel SSPD and SFQ multiplexing circuit and succeeded to read out a photon detection signal from the SSPD via the SFQ circuit that is integrated on the same substrate as the multi-pixel [27]. However, the present detection eciency is 0.25% which is much smaller than the detection eciency of 80% obtained for a single-pixel SSPD. ere are many problems in the manufacturing process to be improved in the future such as generation of separation of SiO silicon thin lm that constructs the photo cavity of SSPD by stress of thin lm in the manufacturing process of the SFQ circuit. Improvement of tting of lm, relaxation of thin lm, etc. should be made.4Future prospectse performance of SSPD increased dynamically in these ve years and the detection eciency already has reached 80%. It is important to realize high detection ef-ciency for various wavelengths to extend application elds and to dierentiate the performance of the SSPD photon detector from the other photon detectors in terms of detec-tion eciency such as high count rate, low dark count rate and low level of jitter. In this case, it is important to know how accurately we understand users’ demand for research and development. NICT is attempting to apply SSPD to uorescence correlation spectroscopy (FCS) for the purpose of applying it to biology and medical treatment, but which cannot be introduced in detail in this article. is is an application focusing on the low-noise and high-speed property that SSPD has no aer-pulse. We have developed an SSPD for visible light used in FCS [28], and succeeded to observe rotation dispersion of a molecule that has been dicult for silicon APD [29][30]. Also, we are developing a large-area multi-pixel targeting application for deep space communication, in collaboration with researchers of Space Communications. We believe that it will be a key to dis-covering new demand, to compete with other existing photon detectors and to widen application elds in the future.AcknowledgmentsWe thank Drs. Shigehito MIKI, research scientist, Taro YAMASHITA, research scientist, Shigeyuki MIYAJIMA, researcher, Masahiro YABUNO, researcher, Akira KAWAKAMI, research scientist and Saburo IMAMURA, technologist, members of the Frontier Research Laboratory. Also, we thank Drs. Shuichi NAGASAWA and Mutsuo HIDAKA of the National Institute of Advanced Industrial Science and Technology for manufacturing the SQC circuit, Dr. Tokuko HARAGUCHI, research scientist of the Frontier Research Laboratory, Prof. Yasushi HIRAOKA of the Graduate School of Frontier Biosciences, Osaka University, Prof. Masataka KINJO of Hokkaido University, Faculty of Advanced Life Science, and Dr. Jotaro YAMAMOTO for useful discussion on FCS. A part of this study was funded by Grants-In-Aid for Scientic Research (Creative, pioneer-ing research conducted by individual researcher (A) No. 26249054).ReferenceR1G. Gol’tsman, O. Okunev, G. Chulkova, A. Lipatov, A. Semenov, K. Smirnov, B. Voronov, A. Dzardanov, C. Williams, and R. 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Yamashita, M. Fujiwara, M. Sasaki, and Z. Wang, “Multichannel SNSPD system with high detection efficiency at telecommunication wavelength,” Opt. Lett. 35, pp.2133–2135, 2010.7http://www.nict.go.jp/press/2013/11/05-1.html8M. Sasaki, M. Fujiwara, H. Ishizuka, W. Klaus, K. Wakui, M. Takeoka, S. Miki, T. Yamashita, Z. Wang, A. Tanaka, K. Yoshino, Y. Nambu, S. Takahashi. A. Tajima, A. Tomita, T. Domeki, T. Hasegawa, Y. Sasaki, H. Kobayashi, T. Asai, K. Shimizu, T. Tokura, T. Tsurumaru, M. Matsui, T. Honjo, K. Tamaki, H. Takesue, Y. Tokura, J. F. Dynes, A. R. Dixon, A. W. Sharpe, Z. L. Yuan, A. J. Shields, S. Uchikoga, M. Legre, S. Robyr, P. Trinkler, L. Monat, J.-B. Page, G. Ribordy, A. Poppe, A. Allacher, O. Maurhart, T. Langer, M. Peev, and 4 Quantum Node Technology62　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 1 (2017)