Tests of quantum mechanics versus local realism using an atomic deuterium source

Abstract

Measurements of the polarization correlation of the two-photons emitted simultaneously by metastable atomic deuterium in a true second order radiative process, are described. Two experiments, one involving the use of a half-wave plate and two linear polarizers, and the other three linear polarizers. have been carried out to investigate the validity of quantum mechanics in hitherto unexplored situations and to test local realistic theories of the type recently proposed by Garucclo and Selleri. The result, of the experiment. provide clear evidence against local realistic theories in which the probability of detection is postulated to be dependent on the angle between a polarization vector I. and a detection vector λ- The quantum mechanical predictions for such experiments, in which non-ideal analysers, were employed, have also been established and have been shown to be in agreement with the experimental results. In addition. the results of circular polarization measurements confirm the conservation of angular momentum along the common axis of detection and give further verification of the correctness of the form of the state vector describing the state of polarization of the two-photons. In another experiment, the effect of an electric field on the polarization properties of the two-photons has been measured for the first time. The Stoke's parameters characterizing the two-photon beam have been determined and the results suggest that the two-photon radiation is partially polarized at 22.5o with respect to the electric field vector. It is suggested that the affect is due to the removal of the degeneracy of the virtual Intermediate P states of the deuterium atom.