Generalized Wick's Theorem for a Boson Field in the Squeezed Vacuum
Alessandro Vaglica, C. Leonardi, G. Vetri · Journal of Modern Optics · 1990
The aim of this paper is to test directly the validity of Wick's theorem for a multimode boson field which is in a squeezed vacuum state. As in the thermal case the fulfilment of this requirement indicates an easy way for the calculus of any order moments of any multivariate operatorial variable whose components are polynomials of the field operators. As a simple application we discuss the first order statistical properties of a properly defined Langevin force expressed as a linear combination of field operators belonging to different modes.