  We demonstrate the successful operation of a multi-element superconducting
nanowire single-photon detector (SSPD) array integrated with a
single-flux-quantum (SFQ) readout circuit in a compact 0.1 W Gifford-McMahon
cryocooler. A time-resolved readout technique, where output signals from each
element enter the SFQ readout circuit with finite time intervals, revealed
crosstalk-free operation of the four-element SSPD array connected with the SFQ
readout circuit. The timing jitter and the system detection efficiency were
measured to be 50 ps and 11.4%, respectively, which were comparable to the
performance of practical single-pixel SSPD systems.
