Patent ID: 8611535

Claim:
A method for characterizing an operational systems parameter of a quantum key distribution system comprising a source of entangled photon pairs, a first single-photon detector coupled to the source of entangled photon pairs by a first optical fiber, and a second single-photon detector coupled to the source of entangled photon pairs by a second optical fiber, the method comprising: measuring a first loss between the source of entangled photon pairs and the first single-photon detector and computing a first transmittance based on the first loss; measuring a second loss between the source of entangled photon pairs and the second single-photon detector and computing a second transmittance based on the second loss; recording first dark counts with the first single-photon detector and computing a first dark count probability based on the recorded first dark counts; recording second dark counts with the second single-photon detector and computing a second dark count probability based on the recorded second dark counts; for each of a plurality of optical powers generated by the source of entangled photon pairs: recording first counts with the first single-photon detector and computing a first count probability based on the recorded first counts; recording second counts with the second single-photon detector and computing a second count probability based on the recorded second counts; recording coincidence counts based on the recorded first counts and the recorded second counts and computing a coincidence count probability based on the recorded coincidence counts; and computing the operational systems parameter based on: the computed first dark count probability; the computed second dark count probability; the plurality of computed first count probabilities; the plurality of computed second count probabilities; and the plurality of computed coincidence count probabilities.