A method of autocalibrating a quantum key distribution (QKD) system (200)
is disclosed. The QKD system includes a laser ((202) that generates
photon signals in response to a laser gating signal (S0) from a
controller (248). The method includes first performing a laser gate scan
(304) to establish the optimum arrival time (T.sub.MAX) of the laser
gating signal corresponding to an optimum--e.g., a maximum number of
photon counts (N.sub.MAX)--from a single-photon detector (SPD) unit (216)
in the QKD system when exchanging photon signals between encoding
stations (Alice and Bob) of the QKD system. Once the optimal laser gating
signal arrival time (T.sub.MAX) is determined, the laser gate scan is
terminated and a laser gate dither process (308) is initiated. The laser
dither involves varying the arrival time (T) of the laser gating signal
around the optimum value of the arrival time T.sub.MAX. The laser gate
dither provides minor adjustments to the laser gating signal arrival time
to ensure that the SPD unit produces an optimum (e.g., maximum) number of
photon counts.