The Leggett-Garg inequality, an analogue of Bells inequality involving correlations of measurements on a system at different times, stands as one of the hallmark tests of quantum mechanics against classical predictions. The phenomenon of neutrino oscillations should adhere to quantum-mechanical predictions and provide an observable violation of the Leggett-Garg inequality. We demonstrate how oscillation phenomena can be used to test for violations of the classical bound by performing measurements on an ensemble of neutrinos at distinct energies, as opposed to a single neutrino at distinct times. A study of the MINOS experiments data shows a greater than $6{sigma}$ violation over a distance of 735 km, representing the longest distance over which either the Leggett-Garg inequality or Bells inequality has been tested.
Download