Patent ID: 7787628

Claim:
A method of distributing a quantum key between a first node and a second node, comprising: by the second node: generating a pulse having multiple photons; splitting the pulse into first and second sub-pulses; phase modulating the first sub-pulse with a secret key; transmitting both the phase-modulated first sub-pulse and the second sub-pulse to the first node; by the first node: receiving the phase-modulated first sub-pulse and the second sub-pulse from the second node; encoding a quantum key bit into one of the sub-pulses received from the second node; transmitting both the phase-modulated first sub-pulse and the second sub-pulse back to the second node; by the second node: receiving the phase-modulated first sub-pulse and the second sub-pulse from the first node; phase modulating the second sub-pulse with the secret key; processing the phase-modulated first sub-pulse and the phase-modulated second sub-pulse in an attempt to detect the quantum key bit.