Time-dependent inhibited spontaneous emission

Summary form only given. When an excited atom is placed in a small reflecting cavity, it is only allowed to radiate into the discrete set of electromagnetic modes that satisfy the boundary conditions in the cavity. If none of these modes are compatile with the spontaneous emission modes of the atom, it will not emit radiation. This phenomenon, known as "inhibited spontaneous emission," has been observed for atoms, for trapped electrons, and for a special type of light source called a parametric downconverter (PDC), in which an incident "pump" photon can spontaneously decay into a pair of lower-energy "signal" and "idler" photons. We can experimentally distinguish photon counting results so long as the Pockel's cell switching time and the jitter or time resolution of the photodetection electronics, is not greater than c, the round-trip time of light in the cavity.