Quantum imaging with continuous variables

A significant fraction of the research activities in the field of quantum imaging concerns optical Parametric Down-Conversion (PDC). Some basic features of this phenomenon will be described in this first chapter of the volume, which deals with the multiphoton regime of the signal-idler field, that one meets in Optical Parametric Amplifiers (OPA) with medium or high gain or in Optical Parametric Oscillators (OPO). In this case, the behavior of the system is naturally described in terms of continuous variables such as field intensity or field quadratures. On the other hand, in the (very) low gain regime of the OPA, one detects coincidences between signal and idler photons and a significant part of the literature on quantum imaging deals with this case, as illustrated in the review article [1]. © 2007 Springer.