Problem of Resonance Fluorescence and the Inadequacy of Spontaneous Emission as a Test of Quantum Electrodynamics
The interaction of a two-level atom with an external electromagnetic field is examined in the framework of quantum electrodynamics, without any assumption about Markoffian behavior or stationarity. It is found that spontaneous emission in the vacuum and the rate of fluorescence in an external field do not depend on quantum properties of the electromagnetic field, whereas the correlation functions do.