Orthogonal sequencing multiplexer for superconducting nanowire single-photon detectors with RSFQ electronics readout circuit

Superconducting nanowire single-photon detectors (SNSPD) offer a high sensitivity up to the single-photon level over a wide spectral range with high counting rate and high detection efficiency. Innovative applications require multi-pixel systems to combine the unique potential of SNSPDs with the advantages of common imaging systems based on standard CMOS/CCD techniques. It has already been demonstrated that rapid single flux quantum (RSFQ) electronics is a convenient candidate to readout SNSPD detectors due to its high-speed data processing and the low power consumption. We propose a new efficient multiplexing technique enabling estimation about the average count rate of each detector with a crogenic pulse merger system based on RSFQ electronics. We discuss the possible scalability of this concept and demonstrate the feasibility by experimental results for a SNSPD array with 4 pixels.