  We put forward and demonstrate experimentally a {\it quantum-inspired}
protocol that allows to quantify the degree of similarity between two spatial
shapes embedded in two optical beams without the need to measure the amplitude
and phase across each beam. Instead the sought-after information can be
retrieved measuring the degree of polarization of the combined optical beam, a
measurement that is much easier to implement experimentally. The protocol makes
use of non-separable optical beams, whose main trait is that different degrees
of freedom (polarization and spatial shape here) can not be described
independently.
