Variable detection probability in two-photon interference

Daohua Wu, Kota Kawamoto, Xiaomin Guo +3 more

Daohua Wu, Kota Kawamoto, Katsuyuki Kasai +2 more

Paul G. Kwiat

Z. Y. Ou, C. K. Hong, L. Mandeļ

A new experimental test of one form of Bell’s inequality is proposed that involves measurement of the joint probability for the detection of two photons as a function of position. The two photons are produced In the process of spontaneous parametric downconversion of pump photons in a nonlinear medium and are allowed to interfere. Although polarizers are used also, the essential variables are the photon positions, which are orthogonal, unlike most polarization states. The probabilities that enter into the Bell inequality, therefore, relate to mutually exclusive events, unlike those in previous tests of locality.

Rainer Kaltenbaek, B. Blauensteiner, Markus Aspelmeyer +2 more

Rupamanjari Ghosh, C. K. Hong, Z. Y. Ou +1 more

A theoretical treatment is given of the situation in which two photons produced in the parametric frequency splitting of light in a nonlinear medium are allowed to interfere. It is shown that there is no interference pattern in the usual sense of quantities that are of the second order in the field, but that fourth-order interference effects are present. These could be demonstrated by placing two photodetectors at positions x,x′ in the interference plane and measuring the joint probability of two detections as a function of x – x′. The probability is predicted to exhibit a cosine modulation with separation x – x′ of close to 100% visibility, even when the integration time in the experiment greatly exceeds the reciprocal bandwidth of the accepted photons. As a result two photons cannot be detected at two points separated by a distance corresponding to an odd number of half-interference fringes. This is an interference effect that violates the laws of classical probability.