Continuous-variable nonlocality test performed over a multiphoton quantum state

We propose to exploit a continuous-variable measurement, based on displacing the input field at different points of the phase space, over a multiphoton state produced by a high-gain optical parametric amplifier. We show that by correlating the different values of the displaced parity operators obtained from the two separated parties, it is possible to violate a Bell's inequality and thus demonstrate the nonlocality of the overall state. The robustness of the results against two independent sources of error, loss and dephasing, is also discussed.