Circuit Quantum Electrodynamics with Transmon Qubits in the Ultrastrong Coupling Regime

Abstract

We propose a circuit model to describe transmon qubits coupled to multimode transmission line resonators. This model has been developed in the frame of circuit quantum electrodynamics and contrasted with available experimental data, and it might be useful for designing future experiments in extreme coupling regimes. In addition, collapses and revivals of qutrit populations are also observed in an extended version of the quantum Rabi model, in both the ultrastrong and deep strong coupling regimes. This work opens the door for using the transmon-resonator system in quantum simulations or quantum computation processes, where such regimes may enhance the toolbox of already available interactions.