Nonlocal continuous-variable correlations and violation of Bell's inequality for light beams with topological singularities
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We consider optical beams with topological singularities which possess Schmidt decomposition and show that such classical beams share many features of two mode entanglement in quantum optics. We demonstrate the coherence properties of such beams through the violations of Bell inequality for continuous variables using the Wigner function. This violation is a consequence of correlations between the (x,px) and (y,py) spaces which mathematically play the same role as nonlocality in quantum mechanics. The Bell violation for the Laguerre-Gaussian beams is shown to increase with higher orbital angular momenta l of the vortex beam. This increase is reminiscent of enhancement of nonlocality for many particle Greenberger-Horne-Zeilinger states or for higher spins. The states with large l can be easily produced using spatial light modulators. 2013 American Physical Society.