Patent ID: 7529373

Claim:
A method of autocalibrating a quantum key distribution (QKD) system having first and second QKD encoding stations, a laser and a single-photon detector (SPD) unit, comprising: a) performing laser gate scanning by: i) sending laser gating signals to the laser to cause the laser to generate photon signals; ii) varying an arrival time T of the laser gating signals over a first range R 1 to vary times at which the photon signals are generated; iii) exchanging the photons signals between the first and second QKD encoding stations and performing first and second encodings of the photon signals at the first and second QKD stations, respectively; iv) detecting a combination of the first and second encoded photon signals at the SPD unit in one of the first and second QKD encoding stations so as to generate photon counts and determining an optimal arrival time T MAX of the laser gating signals that corresponds to a first optimum number of photon counts; and b) performing laser gate dithering by varying the arrival time T of the laser gating signals over a second range R 2 surrounding T MAX to maintain either the first optimum number of photon counts or a second optimum number of photon counts.