We analyze fast interaction cycles in bipartite quantum systems, showing that the statistics in one of the parties (the detector) can be used to determine the two-point correlator of the observable which mediates the coupling in the other (the target). We apply the results to the response of particle detectors coupled to quantum fields and subject to this kind of interactions. We show that, in principle, such a setup can be used to experimentally obtain a direct evaluation of the Wightman function (both its real and imaginary parts) for any field state.

• Received 2 July 2018

DOI:https://doi.org/10.1103/PhysRevD.98.105011