Floquet Engineering the Quantum Rabi Model in the Ultrastrong Coupling Regime

We study the quantum Rabi model for a two-level system coupled to a quantized cavity mode under periodic modulation of the cavity-dipole coupling in the ultrastrong coupling regime, leading to rich Floquet states. Exploiting the quantum vacuum, we show how purely mechanical driving can produce real photons, depending on the strength and frequency of the periodic coupling rate. This scheme is promising for the coherent manipulation of hybrid quantum systems and quantum vacuum effects, with potential applications for quantum state engineering, quantum information processing, and the study of nonequilibrium quantum phenomena.