ENTROPY AND ATTRACTOR DIMENSION AS MEASURES OF THE FIELD-ATOM INTERACTION

We have examined the population oscillation amplitudes, associated attractors, and the order-1 Renyi entropy of Bloch-vector trajectories for a two-level atom interacting with an electromagnetic field, whose phase varies in a two-frequency quasiperiodic manner. Distinct differences in these quantities are observed as the strength of the exciting field varies from weak (nonadiabatic dynamics) to strong (adiabatic dynamics). We find, though, an underlying homology. In all cases the response is two-frequency quasiperiodic with a resulting two-dimensional attractor for the quantum system. Additionally, correlated with observed Rabi resonances, there are abrupt increases in the entropy of the system. A key finding is that Rabi resonances are more than simple increases in the amplitude of a quantum system's population oscillations; the atomic dynamics abruptly becomes more disordered at these resonances.