Master Equations and Sources II

Abstract

Most experiments in quantum optics involve sources of light that might be called photoemissive sources. These axe sources that emit photons irreversibly, to propagate away from the source until they are absorbed in the walls of the laboratory or are detected. Contrast this with the idealized picture of an electromagnetic field confined within a perfect cavity and measured inside the cavity by a detector introduced into that otherwise lossless environment. In the first scenario the act of detecting photons does not directly interfere with the source, since the photons have already left the source, irreversibly, before they encounter the detector. In the second, the detector is a major intrusion; if it turns photons into photoelectrons it removes photons from an otherwise lossless cavity; the description of the cavity field dynamics when the detector is present must be quite different from the description when it is not.