Patent ID: 7046366

Claim:
An optical characteristic measuring apparatus for measuring optical characteristic of a device under test, the apparatus comprising: an entangled photon pair generating element for generating an entangled photon pair, and supplying said device under test with first light which is one of said entangled photon pair; an optical path length changing element for changing at least one of an optical path of second light which is the other one of said entangled photon pair, and an optical path of said first light; a quantum interfering element for transmitting and reflecting said first light transmitting through said device under test, transmitting and reflecting said second light, supplying first multiplexed light which is formed by multiplexing the reflected component of said first light and the transmitted component of said second light, and supplying second multiplexed light which is formed by multiplexing the transmitted component of said first light and the reflected component of said second light; a photon detecting element for detecting a photon in said first multiplexed light and said second multiplexed light; a photon simultaneous detection measuring element for measuring a quantity which changes when the photons are simultaneously detected by said photon detecting element; and a characteristic measuring element for measuring the optical characteristic of said device under test based on the quantity measured by said photon simultaneous detection measuring element.