Cloaking a qubit in a cavity

Cavity and circuit quantum electrodynamics (QED) explore light-matter interaction at its most fundamental level, providing the tools to control the dynamical evolution of single atoms and photons in a deterministic fashion. In this work, we introduce a simple approach to engineer a situation where, in the presence of a cavity drive, an atom decouples from the classical part of the cavity field, perceiving the resonator as if it was in the vacuum state. In this situation, the atom and the cavity undergo Rabi oscillations in the strong coupling regime even when the resonator is loaded with photons, while in the dispersive regime, the atom experiences no ac-Stark frequency shift nor photon-induced dephasing. Since the qubit feels an empty cavity, its manipulation remains unperturbed, maintaining constant gates fidelities in the presence of cavity photons. Exploiting this latter effect, we will show how to accelerate dispersive qubit readout. We will theoretically introduce this approach and then provide an experimental demonstration of the concept using a superconducting transmon qubit. This adds a new element to the toolbox of cavity/circuit QED.