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Resolution of Superluminal Signalling in Non-perturbative Cavity Quantum Electrodynamics

Resolution of Superluminal Signalling in Non-perturbative Cavity Quantum Electrodynamics

Title: Resolution of Superluminal Signalling in Non-perturbative Cavity Quantum Electrodynamics.
When: Monday, May 21, (2018), 12:00.
Place: Department of Theoretical Condensed Matter Physics, Faculty of Sciences, Module 5, Seminar Room (5th Floor).
Speaker: Carlos Sánchez Muñoz, RIKEN Cluster for Pioneering Research, Wako-shi, Japan.

Recent technological developments have made it increasingly easy to access the nonperturbative regimes of cavity quantum electrodynamics known as ultrastrong or deep strong coupling, where the light–matter coupling becomes comparable to the bare modal frequencies [1].

In this talk, I will discuss the adequacy of the broadly used single-mode cavity approximation to describe such regimes. We have demonstrated that, in the non-perturbative light–matter coupling regimes, the single-mode models become unphysical, allowing for superluminal signalling [2]. Moreover, considering the specific example of the quantum Rabi model, we show that the multi-mode description of the electromagnetic field, necessary to account for light propagation at finite speed, yields physical observables that differ radically from their single-mode counterparts already for moderate values of the coupling. Our multimode analysis also reveals phenomena of fundamental interest on the dynamics of the intracavity electric field, where a free photonic wavefront and a bound state of virtual photons are shown to coexist.


  1. Forn-Díaz, P., Lamata, L., Rico, E., Kono, J., & Solano, E. (2018). arXiv:1804.09275.
  2. Sánchez Muñoz, C., Nori, F., and De Liberato, S., Nature Communications (2018) 9:1924.

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