Characterizing Polariton States in the Non-Dispersive regime of cQED

A superconducting qubit coupled to a resonator is currently the building block of multiple quantum computing as well as quantum optics experiments. A typical qubit-resonator system is coupled in the dispersive regime, where the detuning between the qubit and resonator is much greater than the coupling between them. In this work, we fabricated and measured a superconducting transmon qubit coupled to a lumped element resonator in non-dispersive regime. The dressed states formed by mixing the bare qubit and resonator states can be further mixed by applying a drive on the qubit, leading to the formation of polariton states. We report experimental studies of transitions between polariton states at varying driving strengths and frequencies. We observe the effects of the non-dispersively coupled higher transmon levels in our system. We also report close agreement with numerical results obtained from a driven Jaynes–Cummings Model beyond the dispersive regime.