Basis-independent tomography and nonseparability witnesses of pure complex vectorial light fields by Stokes projections

Complex vectorial light fields, nonseparable in their polarization and spatial degree of freedom, are of relevance in a wide variety of research areas encompassing microscopy, metrology, communication, and topological studies. Controversially, they have been suggested as analogs to quantum entanglement, raising fundamental questions on the relation between nonseparability in classical systems, and entanglement in quantum systems. We perform basis-independent tomography of arbitrary pure vectorial light fields using spatially resolved Stokes projections. Moreover, we propose and demonstrate that concurrence, as a nonseparability witness for any pure vectorial light field, can be extracted from global Stokes projections, without assessing the spatial degree of freedom.