Robust Measurement of the Concurrence of Vector Light Beams

Coherent vector light beams with spatially structured polarization exhibit intrinsic nonseparability between the spatial amplitude and polarization-state degrees of freedom, quantified by optical concurrence-a measure formally analogous to quantum concurrence characterizing entanglement in bipartite quantum systems. Here, we introduce a method to measure the optical concurrence of monochromatic vector beams by encoding the nonseparability into the coherence properties of a partially coherent light field. This enables the concurrence to be retrieved from either a single-shot speckle pattern or a single-pixel temporal intensity measurement. Our technique is efficient and alignment-free, eliminating the need for polarization-resolving components and opening new possibilities in optical communication, sensing, and classical analogs of quantum information protocols.