We investigate the dynamics of superconducting qubits coupled to high impedance Josephson waveguides. This novel architecture pushes microwave quantum optics in the so-called ultra-strong coupling regime, where the decay rate of an emitter becomes comparable to its transition frequency. In turn, various standard quantum optics phenomena, such as spontaneous emission, resonance fluorescence, or the dressed atom picture, are considerably affected by many-body effects.

We will present new theoretical methodologies that have been developed to address these issues, and discuss the status of the ongoing experiments at the Neel Institute and elsewhere.

Contact : denis.basko@lpmmc.cnrs.fr