Contextuality within quantum mechanics manifested in subensemble mean values

Abstract

For spin-1/2 particles, using a suitable Mach-Zehnder-type setup with a spin-flipper, we argue that it is a direct consequence of the quantum mechanical treatment that an experimentally verifiable subensemble mean of the measured values of an arbitrarily chosen spin variable exhibits dependence on the choice of a comeasurable 'path' observable. This, in turn, enables inferring path-spin contextuality at the level of individual measured values of spin that are predetermined using a relevant hidden-variable model applied to our setup.