33rd RQC Seminar
Mr. Alberto Mercurio
(Dipartimento di Fisica della Materia e Scienze della Terra, Università degli Studi di Messina, Italy)
16:00-17:00 (JST), March 22, 2023 (Wednesday)
Hybrid (Zoom / Wako Welfare and Conf. 2F Large Meeting Room RIKEN Wako branch)
Exploring the Frontier of Coherent and Incoherent Processes in Ultrastrong Coupled Systems
In recent years, the ultrastrong coupling regime has emerged as a new frontier in cavity-quantum electrodynamics (cavity-QED) systems. This regime occurs when the light-matter interaction rate exceeds the bare transition frequencies of the subsystems, leading to a significant change in the dynamics of the system compared to other light-matter interaction regimes such as weak or strong coupling. In ultrastrong coupling systems, the standard quantum optics master equation may fail to correctly describe the interaction of the system with the reservoirs and, without a proper analytical derivation, there can be a violation of gauge invariance.
In this seminar, we present two recent studies that focus on the dynamics of ultrastrong coupling systems. The first one addresses the photon-flux emission rate of a two-level atom interacting with a quantized single-mode electromagnetic field, which is described by the quantum Rabi model (QRM). This study considers an incoherent excitation of the two-level atom and analyzes the dependence of the emission spectra on the coupling strength and effective temperatures. The second study investigates the occurrence of spontaneous Raman scattering in cavity-QED systems in the ultrastrong coupling regime. We provide a quantum mechanical description of the effect and show that ultrastrong light-matter coupling is a necessary condition for the observation of Raman scattering in these systems. These results open up new avenues for the characterization of cavity-QED systems and the generation of quantum states of light.