Energy diffusion in a strong noise field

It is shown that, under the action of a perturbation with a continuous frequency spectrum, the rate of the energy diffusion of a quantum oscillator is described by an expression that formally follows from the Fermi golden rule, even when the conditions of the validity of this rule are violated, that is, in the parameter range where the transition rate is comparable to the frequency of transition between the system levels or exceeds it. This circumstance provides the quantum-classical correspondence for the energy diffusion rate in the quasi-classical domain.