Method and device to synchronize and acquire twin photons for a method of quantum cryptography

摘要

Synchronization method and acquisition twin photons for a method of quantum cryptography, comprising the steps of: - generating entangled photon pairs, the photons in each pair are of opposite polarization; - supplying a first photon in the pair through a first channel (7) communicating at a first station (4) for receiving having a first clock (62a) generating a time reference for the first receiving station; - supplying a second photon in the pair through a second channel (8) to a second communication station (5) receiving a second clock having (62b) generating a time reference for the second receiving station; - compare, in each receiving station, the polarization of each photon received with a first baseline or base randomly selected second reference; each baseline comprising two perpendicular axes, and being angularly spaced bases first and second reference by a given angle; - generating a synchronization signal to activate the first clock and the second clock; and - search twin pairs photons received at the two stations (4, 5) receiving at the same moment measured on the basis of information provided by the respective clocks; wherein the step of searching twin photon pairs comprises the steps of: - measuring, at each station (4, 5) receiving the time difference DT between the acquisition time tn of a photon and the instant of acquisition TN- one photon preceding received: DT = tn - tn-1 - recognizing a pair of twin photons when the absolute value of the difference between the difference DTa time as a first station (4) for receiving and difference corresponding time DTb as a second station (5) reception is less than a time window matching: | DTa - DT | W: and - repeating the steps of measurement and recognition.