Abstract: Method and apparatus for synchronizing and locking clocks identifies entangled pairs of photons by comparing a first and second list of measured state values of single photons, wherein the first list is compiled by photon arrival times measured using a first clock and the second list is compiled by photon arrival times measured using a second clock. Entangled pairs of photons are identified by a match of the measured state values of single photons in their respective lists. Elapsed times of the first and second clocks are determined by taking the difference between arrival times of respective identified entangled pairs of photons measured using their respective clocks. A rate of one of the first and second clocks is changed based on a difference between the elapsed times, thereby synchronizing the first and second clocks. Clocks are locked by repeating.

Abstract: A method of generating a verification code includes generating a plurality of first photons and a plurality of second photons that are entangled in a first basis, which is time, and entangled in a second basis comprising a first and second state. The plurality of first photons are provided to a first device where the arrival time and an associated first or second state of the plurality of first photons are measured. An ordered list of the measured time of arrival of the plurality of first photons are generated at the first device. The plurality of second photons are provided to a second device. A time of arrival and an associated first or second state of the plurality of second photons are measured at the second device. An ordered list of the measured time of arrival of the plurality of second photons are generated at the second device.