Patent ID: 7450718

Claim:
A method of synchronizing the operation of a two-way QKD system having a first QKD station (BOB) with a quantum laser for generating quantum signals and a single-photon detector (SPD) unit gated by detector gating signals, wherein BOB is optically coupled to a second reflecting QKD station (ALICE) via an optical fiber link that carries the quantum signals, the method comprising: sending a synchronization (sync) signal in one direction from ALICE to BOB over the optical fiber link; phase locking the sync signal at BOB; wherein the quantum laser is responsive to a timed laser control signal and including dithering the timing of the laser control signal so as to operate the QKD system in three different operating states each having a different laser control signal timing; for each operating state, counting the number of detected quantum signals at the SPD unit for a given number of detector gating signals; and placing the QKD system in the operating state having the greatest number of detected quantum signals.