A model used in quantum optics and atomic physics to describe the interactions between an atom with two energy levels and a quantized mode of an electromagnetic field. This model, which was put forward by the American physicists Edwin Jaynes (1922–98) and Fred Cummings in 1963, has proved to be very useful in establishing which aspects of quantum optics are purely quantum mechanical and which can be dealt with by using quantum mechanics for the two-level atom and classical electrodynamics for the electromagnetic field.