  We developed a four-channel superconducting nanowire single-photon detector
system based on a Gifford-McMahon cryocooler. All channels showed a system
detection efficiency (at a 100 Hz dark-count rate) higher than 16% at 1550 nm
wavelength, and the best channel showed a system DE of 21% and 30% at 1550 nm
and 1310 nm wavelength, respectively.
