Measuring correlations in non-separable vector beams using projective measurements

TL;DR

This paper demonstrates experimentally that locally correlated systems with spin and orbital angular momentum can violate Bell's inequality, challenging hidden variable theories and advancing quantum correlation measurement techniques.

Contribution

It introduces a linear, achromatic modified Sagnac interferometer for projecting orbital angular momentum states and measures correlations with spin, showing Bell's inequality violation in such systems.

Findings

Violation of Bell's inequality in locally correlated spin and orbital angular momentum systems

Development of a novel interferometer for orbital angular momentum projection

Experimental evidence supporting quantum nonlocality in local degrees of freedom

Abstract

Doubts regarding the completeness of quantum mechanics as raised by Einstein, Podolsky and Rosen(EPR) have predominantly been resolved by resorting to a measurement of correlations between entangled photons which clearly demonstrate violation of Bell's inequality. This article is an attempt to reconcile incompatibility of hidden variable theories with reality by demonstrating experimentally a violation of Bell's inequality in locally correlated systems whose two degrees of freedom, the spin and orbital angular momentum, are maximally correlated. To this end we propose and demonstrate a linear, achromatic modified Sagnac interferometer to project orbital angular momentum states which we combine with spin projections to measure correlations.