Weak-Coupling-Like Time Evolution of Driven Four-Level Systems in the Strong-Coupling Regime

It is shown analytically that there exists a natural basis in terms of which the nonperturbative time evolution of an important class of driven four-level systems in the strong-coupling regime decouples and essentially reduces to the corresponding time evolution in the weak-field regime, exhibiting simple Rabi oscillations between the different relevant quantum states. The predictions of the model are corroborated by an exact numerical calculation.