Light Source Monitoring in Quantum Key Distribution With Single-Photon Detector at Room Temperature

Photon number resolving monitoring is a practical light source monitoring scheme in quantum key distribution (QKD) systems and can, effectively, reduce the risks due to the effects of untrusted sources. This scheme requires a single-photon detector, normally working at low temperature to suppress its dark count rate. In this paper, we use a room-temperature detector and show that the dark count rate is nearly irrelevant to the monitoring performance in our scheme, thus can sufficiently reduce the afterpulsing effect of the detectors as well as relax the requirements on their working conditions and integration complexity, which would be highly desirable for practical high-speed QKD systems with imperfect sources. Furthermore, the influences of parameter drifts at room temperature are analyzed, and the monitoring scheme is testified in a real QKD system.