Patent ID: 7606371
Filing Date: 2009-10-20
Classification: H04L

Abstract:
1. A quantum key distribution (QKD) system comprising: a first QKD station that includes first and second interferometer loops, wherein the first interferometer loop generates two quantum signals from a single quantum signal generated in the first QKD station; a second QKD station optically coupled to the first QKD station via an optical fiber connection, wherein the second QKD station is adapted to randomly modulate at least one of the two quantum signals and return the two quantum signals to the first QKD station over the optical fiber link; a signal-directing element having first and second outputs and arranged in the first QKD station, and that directs the two quantum signals to the second QKD station through the first output and directs the two returned quantum signals only to the second interferometer loop through the second output; and a detection stage coupled to an output end of the second interferometer loop and adapted to detect two interfered quantum signals created by the second interferometer loop from the two returned quantum signals.