1- and 3-photon dynamical Casimir effects using nonstationary cyclic qutrit

We consider the nonstationary circuit QED setup in which a 3-level artificial atom in the $\Delta$-configuration interacts with a single-mode cavity field of natural frequency $\omega$. It is demonstrated that when some atomic energy level(s) undergoes a weak harmonic modulation, photons can be generated from vacuum via effective 1- and 3-photon transitions, while the atom remains approximately in the ground state. These phenomena occur in the dispersive regime when the modulation frequency is accurately tuned near $\omega$ and $3\omega$, respectively, and the generated field states exhibit strikingly different statistics from the squeezed vacuum state attained in standard cavity dynamical Casimir effect.