Patent ID: 7609382

Claim:
A method of detecting entangled-photon pairs configured to have a predetermined quantum state relationship with a prepared target medium, each entangled-photon pair comprising a signal photon and an idler photon, the method comprising: supplying the target medium; configuring a quantum state of the target medium relative to the entangled-photon pairs thereby producing the prepared target medium, wherein the prepared target medium has a quantum state configured to substantially increase an entangled two-photon cross-section for the entangled-photon pairs and decrease a random two-photon absorption cross-section for the entangled-photon pairs; providing entangled-photon pairs, at least a first portion of the entangled-photon pairs having an entanglement time and an entanglement area to substantially increase an associated entangled two-photon cross-section of the prepared target medium; ensuring that at least a second portion of the entangled-photon pairs have an energy distribution between the signal photon and the idler photon to substantially decrease an associated random two-photon absorption cross section of the target medium; directing photons included in the first portion and the second portion to the target medium; detecting at least one entangled-photon pair being absorbed by the target medium; and outputting an electrical signal representing said detecting.