Dynamical Casimir effect via four- and five-photon transitions using a strongly detuned atom

The scenario of a single-mode cavity with harmonically modulated frequency is revisited in the presence of strongly detuned qubit or cyclic qutrit. It is found that when the qubit frequency is close to $3\nu$ there is a peak in the photon generation rate via four-photon transitions for the modulation frequency $4\nu$, where $\nu$ is the average cavity frequency. Effective five-photon processes can occur for the modulation frequency $5\nu$ in the presence of a cyclic qutrit, and the corresponding transition rates exhibit series of peaks. Closed analytical description is derived for the unitary evolution, and numeric simulations indicate the feasibility of multi-photon dynamical Casimir effect under weak dissipation.