EPR experiment and two-photon interferometry: Report of a two-photon interference experiment

After a very brief review of the historical EPR experiments, this paper reports a new two-photon interference type EPR experiment. A two-photon state was generated by optical parametric down conversion. Pairs of light quanta with degenerate frequency but divergent directions of propagation were sent to two independent Michelson interferometers. First- and second-order interference effects were studied. Different from other reports, we observed that the second-order interference visibility vanished when the optical path difference of the interferometers were much less than the coherence length of the pumping laser beam. However, we also observed that the second-order interference behaved differently depending on whether the interferometers were set at equal or different optical path differences.Presented at the International Workshop on Squeezed and Correlated States, Moscow, December 3–7, 1990.