Patent ID: 7587049

Claim:
An actively stabilized one-way QKD system, comprising: a first QKD station that emits a quantum signal and a control signal and that has a first interferometer loop; a second QKD station optically coupled to the first QKD station via an optical fiber link and that has a second interferometer loop and a detection stage operably coupled to an output of the interferometer loop, wherein the second interferometer loop has an arm with a phase shifter; a polarization control stage arranged immediately upstream of the second QKD station; a controller coupled to the detection stage and the phase shifter; and wherein the quantum signal and the control signal traverse the same path through the first interferometer loop, the optical fiber link, the polarization control stage and the second interferometer loop, and wherein the control signal is detected by the detection stage and is used by the controller to actively adjust the phase shifter to phase-stabilize the second interferometer loop.