Observation of two-photon interference in a dual-beam Michelson interferometer
Paul G. Kwiat, William A. Vareka, R. Y. Chiao, C. K. Hong, Howard Nathel · 1990
Nonlocal effects in quantum mechanics associated with entangled states have been the subject of much recent interest.1,2 Franson1 suggested that one can observe a violation of Bell's inequalities for position and time by use of two spatially separated interferometers. We report on the observation of a closely related two-photon interference. A signal photon at frequency ωs and an idler photon at frequency ωi = ωp – ωs are created simultaneously, i.e., as a conjugate pair, in parametric fluorescence inside a KDP crystal from the annihilation of a single UV pump photon with frequency ωp3.