Quantum mechanical effect of path-polarization contextuality for a single photon

TL;DR

This paper demonstrates a quantum mechanical effect of contextuality between path and polarization in a single photon using a Mach-Zehnder setup, showing measurement outcomes depend on measurement choices without invoking realism or hidden variables.

Contribution

It reveals a novel form of quantum contextuality involving path and polarization degrees of freedom in single photons, independent of entanglement or hidden variables.

Findings

Contextuality affects subensemble measurement statistics

Effect depends on measurement choice at exit channels

No effect observed for the entire photon ensemble

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 \emph{either} of the two exit channels of the MZ setup used, the empirically verifiable \emph{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 \emph{whole ensemble} of photons emerging from the two exit channels of the MZ setup.