Patent ID: 7876901

Claim:
A system for deciphering information encoded using a quantum key by determining the polarization states of the signal photons encoding the quantum key, comprising: a quantum entangling probe comprising: an input for receiving signal photons having polarization states encoding a quantum key; a single-photon source for producing a probe photon; a probe photon polarizer; a quantum controlled-NOT (CNOT) gate configured to provide entanglement of a signal photon with the probe photon so that the signal photon and the probe photon have entangled polarization states to obtain information on the quantum key; the quantum controlled-NOT (CNOT) gate comprising first and second outputs; the first output operating to output the probe photon and the second output operating to output the signal photon; a beam splitter configured to separate the possible polarization states of the probe photon; and two photodetectors configured to measure the polarization state of the probe photon; wherein the quantum key is used for data transmission to an intended receiver and the quantum key is being intercepted by an unintended recipient and wherein the intended receiver is not able to determine that the quantum key has been intercepted and wherein the quantum CNOT gate is configured to provide entanglement of the signal photon with the probe photon so as to obtain Renyi information from the signal photon.