University of Freiburg

Institute of Physics

Quantum Optics and Statistics


Effective mode theory for open quantum systems

„In the study of light interacting with matter, resonator quantum electrodynamics systems have the important property to enable strong interactions, i.e. to enter the non-perturbative regime. The associated strong-coupling phenomena in high quality cavities have led to fascinating experiments showing how to control individual quantum systems. In the last decade, different kinds of resonators have moved into the focus of attention. In particular, strong coupling can now also be achieved in lossy resonators. Plasmonic systems, for example, achieve extreme field enhancements due to their size, on the order of a few wavelengths, but simultaneously do not confine the field for a long time.

From a theory perspective, this strongly leaky regime is particularly challenging. Indeed, historically, few-mode models – such as the Jaynes-Cummings model and its generalizations – have been an indispensable and effective tool in studying strong coupling resonator QED. However, these models break down at larger losses due to the appearance of non-Markovian effects and overlapping modes.

We investigate how to tackle these challenges. By exploiting the aforementioned approaches to their limits of validity and studying the coupling between the lossy resonator and the environment, we intend to extend few-mode models beyond the referred limitations using recently developed concepts from the theory of open quantum systems.“