Interferometric measurement system using time-correlated photons

A method of optical interferometry, the method comprising:

• a) simultaneously generating a set of four time-correlated photons such that a first pair of photons in the set of four time-correlated photons are time correlated indicating that a second pair of photons in the set of four time-correlated photons are time correlated and such that a photon from the first pair of photons, another photon from the first pair of photons, a photon from the second pair of photons, and another photon from the second pair of photons emerge at spatially separate locations;
• b) interferometrically combining the photon from the first pair of photons and the other photon from the first pair of photons;
• c) detecting a first signal from the interferometrically combined photon from the first pair of photons and the other photon from the first pair of photons;
• d) detecting a second signal from the interferometrically combined photon from the first pair of photons and the other photon from the first pair of photons;
• e) detecting a third signal in response to measurement of the photon from the second pair of photons;
• f) detecting a fourth signal in response to measurement of the other photon from the second pair of photons;
• and
• g) determining a coincidence in response to the detection of the photon from the second pair of photons and in response to detection of the other photon from the second pair of photons, thereby identifying the set of four time-correlated photons and heralding an interferometric measurement from the detected first signal and the detected second signal from the interferometrically combined photon from the first pair of photons and the other photon from the first pair of photons.

An optical interferometer comprising:

• a) an optical source configured to simultaneously generate a set of four time-correlated photons comprising a first pair of photons and a second pair of photons;
• b) an interferometer configured to receive a photon from the first pair of photons and configured to receive another photon from the first pair of photons;
• c) a first and a second detector configured to generate an electrical signal in response to measurements of an output of the interferometer;
• d) a third detector configured to generate an electrical signal in response to measurement of a photon from the second pair of photons;
• e) a fourth detector configured to generate an electrical signal in response to measurement of another photon from the second pair of photons;
• and
• f) a processor configured to determine a coincidence of the generated electrical signals in response to measurements of the second pair of photons, thereby identifying the set of four time-correlated photons and heralding an interferometric measurement from the generated electrical signals of the first and second detectors.