  Superconducting nanowire single-photon detectors are an enabling technology
for modern quantum information science and are gaining attractiveness for the
most demanding photon counting tasks in other fields. Embedding such detectors
in photonic integrated circuits enables additional counting capabilities
through nanophotonic functionalization. Here we show how a scalable number of
waveguide-integrated superconducting nanowire single-photon detectors can be
interfaced with independent fiber optic channels on the same chip. Our
plug-and-play detector package is hosted inside a compact and portable
closed-cycle cryostat providing cryogenic signal amplification for up to 64
channels. We demonstrate state-of-the-art photon counting performance with up
to 60 % system detection efficiency and down to 26.0 ps timing accuracy for
individually addressable detectors. Our multi-channel single photon receiver
offers exciting measurement capabilities for future quantum communication,
remote sensing and imaging applications.
