Quantum Mechanical Effect of Path-polarization Contextuality for a Single Photon

Abstract

Using measurements pertaining to a suitable Mach-Zehnder (MZ) type setup, a curious quantum mechanical effect of contextuality between the path and the polarization degrees of freedom of a polarized photon is demonstrated, without using any notion of realism or hidden variables—an effect that holds good for the product as well as the entangled states. This form of experimental context-dependence is manifested in a way such that at either of the two exit channels of the MZ setup used, the empirically verifiable subensemble statistical properties obtained by an arbitrary polarization measurement depend upon the choice of a commuting (comeasurable) path observable, while this effect disappears for the whole ensemble of photons emerging from the two exit channels of the MZ setup.