34th RQC Seminar
Mr. Fabio Mauceri
(Dipartimento di Fisica della Materia e Scienze della Terra, Università degli Studi di Messina, Italy）
ハイブリッド（Zoom ・ 理研 和光事業所 統合支援棟2階 大会議室）
Nonlinear-resonator quantum Rabi model and dephasing in ultrastong and deepstrong coupling regimes
Experimental achievements in the recent years have made possible reaching the ultrastrong and the deep strong coupling regime between light and matter. As shown in recent works, extra care is needed when constructing gauge-independent theories in the presence of approximations as the truncation of the Hilbert space of the matter system. Such a truncation can ruin gauge invariance leading to nonphysical results, especially when the light-matter interactions strength is very high. In this talk I will show how to face this issue and obtain correct gauge-independent results and apply this to two examples.
The first one, is a two-level atom interacting with a single-mode nonlinear electromagnetic resonator with coupling strengths ranging from zero to the deep strong coupling regime and I will show how how to solve gauge issues to provide a consistent nonlinear-resonator quantum Rabi model. The second one is an analysis of pure dephasing for two prototypical models of cavity QED: the quantum Rabi model and the Hopfield model. I will show that the interaction between light and matter can significantly affect the form of a stochastic perturbation describing the dephasing of one of the components, depending on the adopted gauge.