Search

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., Comment: 7 pages, 3 figures

The Schr\"odinger equation in phase space is used to calculate the Wigner function for the Helium atom in the approximation of a system of two oscillators. Dissipation effect is analysed and the non-classicality of the state is studied by the non-classicality indicator of the Wigner function, which is calculated as a function of the dissipation parameter.