Long-distance quantum key distribution in optical fibre

Abstract

Use of low-noise detectors can both increase the secret bit rate of\nlong-distance quantum key distribution (QKD) and dramatically extend the length\nof a fibre optic link over which secure key can be distributed. Previous work\nhas demonstrated use of ultra-low-noise transition-edge sensors (TESs) in a QKD\nsystem with transmission over 50 km. In this work, we demonstrate the potential\nof the TESs by successfully generating error-corrected, privacy-amplified key\nover 148.7 km of dark optical fibre at a mean photon number mu = 0.1, or 184.6\nkm of dark optical fibre at a mean photon number of 0.5. We have also exchanged\nsecret key over 67.5 km that is secure against powerful photon-number-splitting\nattacks.\n