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

T. Haji-Hassan

Published Jan 1, 1987• 0 citations
OpenAlex

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 \nmeasurements 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.

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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 \nmeasurements 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.
Measurements have been made of the polarization properties of the two photons emitted in the decay of metastable atomic deuterium in an experiment in which three linear polarizers, instead of the normal two, are used. The quantum-mechanical predictions for these imperfect polarizers have been calculated and shown to be in good agreement with the experimental results. The results have also been used to test local realistic models which are capable of explaining all existing two-polarizer-type experiments, and have provided conclusive evidence against these theories.
A 1-keV metastable atomic deuterium [D(2S)] beam of density about 104 atoms cm-3 has been produced by charge-exchange, in caesium vapour, of deuterons extracted from a radio-frequency ion source. The linear and circular polarisation correlation of the two photons emitted spontaneously by metastable atomic deuterium in a true second order radiative process have been measured for the first time. While the circular polarisation results confirm the conservation of angular momentum along the common axis of detection, the correlation in linear polarisation has been applied in a test of Bell’s Inequality which allows a quantitative distinction to be made between the predictions of Quantum Mechanics and local realistic ("hidden variable") theories. The results are in agreement with Quantum Mechanics and violate Bell’s Inequality by almost two standard deviations.
We report a novel method of determining the coherence length of photons produced in the two-photon decay of metastable atomic deuterium by observing the depolarization of the photons in what is essentially a true single-photon interference experiment. In the Stirling source two photons propagating in the ±z directions are detected in coincidence. The degree of polarization of the radiation emerging from a multiwave plate placed on one side of the source as a function of the optical path difference 6 introduced by the multiwave plate between the orthogonally polarized components is determined by measuring the Stokes' parameters. The results confirm the dependence of the depolarizing effect of the multiwave plate on 6, agree with the quantum mechanical predictions and allow a measurement to be made of the coherence length of single photons of the two-photon pair. \nWe also report the results t>f an experiment which, for the first time, demonstrates the action of an achromatic half-wave plate on the polarization state of the two-photon radiation emitted by atomic deuterium in the metastable 2Sv, state The results agree with the quantum mechanical predictions and confirm the hypothesis of Breit and Teller that the fine and hyperfine interaction play no role in the emission process.