Parallel Bias and Readout Techniques Toward Realization of Large-Scale SSPD Array With SFQ Circuit

Toward the realization of a large-scale superconducting nanowire single-photon detector (SSPD) array system, we present the parallel bias operation of an SSPD array in which all elements are simultaneously biased in parallel by a single voltage source. We fabricated an SSPD array with uniform quality and implemented the device with/without single-flux-quantum (SFQ) readout circuit in a compact 0.1 W Gifford-McMahon cryocooler. By applying the time-resolved readout setup, we measured histograms of time-correlated single-photon counts to verify the parallel bias operation of the SSPD array with conventional and SFQ readout techniques. As a result, we confirmed crosstalk-free parallel bias operation of the four-element SSPD array by conventional and SFQ readouts.