CRYPTOGRAPHIC RECEIVER

摘要

A cryptographic receiver (10) includes photon detectors (52, 54, 56, 58) arranged to detect photons arriving from filters (22) and (24). A fibre coupler (14) randomly distributes each received photon (16) from an optical fibre to one of two photon channels (18, 20). The filters (22, 24) are each unbalanced Mach-Zehnder interferometers with a phase modulator (34, 44) in one arm (28, 38). The filters (22, 24) impose non-orthogonal measurement bases on photons within the respective channels (18, 20). A signal processor (60) derives a cryptographic key-code by analysis of signals received from the photon detectors (52, 54, 56, 58).