Covert information sharing via ghost displacement

Abstract

Ghost imaging research has demonstrated that it is possible to reproduce an image of an object that has not interacted with the imaging light. In this paper we describe theoretically and demonstrate experimentally a coherent displacement imposed nonlocally on one mode of a two-mode state, replicating the ghost imaging effect in the coherent-state basis. We use it to show the possibility of a form of covert information sharing via a ghost displacement operation which enables two distant users to retrieve amplitude and phase information modulated onto a phase-independent thermal state, based only on correlated detection statistics. The displacement operation also provides a secondary probabilistic amplification effect on the mean photon number of the displaced thermal state, which could be exploited for covert quantum illumination experiments.