Patent ID: 8675876
Filing Date: 2014-03-18
Classification: H04L

Abstract:
1. A method for quantum key distribution comprising: a) providing pulses of coherent light having a time spacing T between adjacent pulses at a transmitter; b) phase modulating the pulses randomly at the transmitter such that each adjacent pair of pulses is either in phase or out of phase, wherein the modulation applied to each pulse is recorded to provide modulation times; c) adjusting the intensity of the pulses such that an average number of photons per transmitted pulse is a predetermined value μ less than unity; d) transmitting the pulses from the transmitter to a receiver over a channel having a transmittance α; e) demodulating the received pulses by passing them through a two arm interferometer having a time delay difference equal to T, wherein the interferometer has two outputs (O f) detecting demodulated pulses with the detectors to provide detection events, each detection event having a detection time, wherein detectors D g) providing the detection times to the transmitter; i) comparing the detection times to the modulation times to deduce at the transmitter which of the detectors in the receiver is associated with each of the detection events; wherein a secure key generation rate R wherein R wherein μ is predetermined such that R