Ultrastrong coupling of a qubit with a nonlinear optical resonator
Fabio Mauceri, Alberto Mercurio, Salvatore Savasta, Omar Di Stefano · Physical Review A · 2022
The authors study the quantum Rabi model in the ultrastrong regime in the presence of cavity nonlinearities and identify inconsistencies from various nonlinear Hamiltonians. To resolve the issues, the authors develop a microscopic theory and provide a consistent nonlinear-resonator quantum Rabi model satisfying the gauge principle.