We report the fabrication of a superconducting nanowire single-photon detector (SSPD or SNSPD) with an ultralow dark count rate. By introducing optical band-pass filters at the input of the SSPD and cooling the filters at 3 K, the dark count rate is reduced to less than 1/100 at low bias. An SSPD with 0.1 cps dark count rate and 5.6% system detection efficiency at 1550 nm wavelength is obtained. We show that a quantum key distribution (QKD) over 300 km of fiber is possible based on a numerical calculation assuming a differential phase shift QKD protocol implemented with our SSPDs.
@article{arxiv.1307.0893,
title = {Superconducting nanowire single-photon detector with ultralow dark count rate using cold optical filters},
author = {H. Shibata and K. Shimizu and H. Takesue and Y. Tokura},
journal= {arXiv preprint arXiv:1307.0893},
year = {2014}
}