Proposed molecular test of local hidden-variables theories

Abstract

The inefficiency of detectors of low-energy photons permits a loophole in the experimental refutation of local hidden-variables theories by observations of polarization correlations. A specific local hidden-variables model of Clauser and Horne shows that a hypothetical selectivity of detectors can yield the counting rates predicted by quantum mechanics. We therefore derive a new Bell-type inequality, which takes detection inefficiency into account. The loophole can then be blocked by observing spin correlations of atom pairs in an electronic singlet state, if both spin analysis and detection are sufficiently efficient. We propose to create Na atom pairs in the electronic singlet state, by using the induced Raman effect to excite ${\mathrm{Na}}_2$ molecules in the electronic ground state $X{}_{}{}^1{}_{}{}^{}{\Sigma }_g_{}^{+}{}_{}{}^{}$ to the continuum of the electronic ground state. Two laser beams are to be used, one for excitation to a virtual intermediate state in $A{}_{}{}^1{}_{}{}^{}{\Sigma }_u_{}^{+}{}_{}{}^{}$, one to induce the downward transition to the final state. The ensemble needed to test the new inequality consists of those pairs which enter the respective collimating apertures of two Stern-Gerlach analyzers.