Semiclassical Dynamics of the Jaynes-Cummings Model

The semiclassical approximation of coherent state path integrals is employed to study the dynamics of the Jaynes-Cummings model. Decomposing the Hilbert space into subspaces of given excitation quanta above the ground state, the semiclassical propagator is shown to describe the exact quantum dynamics of the model. We also present a semiclassical approximation that does not exploit the special properties of the Jaynes-Cummings Hamiltonian and can be extended to more general situations. In this approach the contribution of the dominant semiclassical paths and the relevant fluctuations about them are evaluated. This theory leads to an accurate description of spontaneous emission going beyond the usual classical field approximation.