A Mean-Field Treatment of Vacuum Fluctuations in Strong Light-Matter Coupling

TL;DR

This paper introduces a mean-field approach that accurately models vacuum fluctuations in strong light-matter interactions, preventing unphysical energy transfer and aligning well with quantum results, enabling efficient simulations of complex systems.

Contribution

The authors develop a novel mean-field method that explicitly includes vacuum fluctuations with a population-dependent scaling, improving accuracy in strong coupling regimes.

Findings

Prevents unphysical energy transfer in classical models

Achieves excellent agreement with quantum calculations

Enables efficient modeling of large optical mode systems

Abstract

Mean-field mixed quantum--classical dynamics could provide a much-needed means to inexpensively model quantum electrodynamical phenomena, by describing the optical field and its vacuum fluctuations classically. However, this approach is known to suffer from an unphysical transfer of energy out of the vacuum fluctuations when the light--matter coupling becomes strong. We highlight this issue for the case of an atom in an optical cavity, and resolve it by introducing an additional set of classical coordinates to specifically represent vacuum fluctuations whose light--matter interaction is scaled by the instantaneous ground-state population of the atom. This not only rigorously prevents the aforementioned unphysical energy transfer, but is also shown to yield a radically improved accuracy in terms of the atomic population and the optical field dynamics, generating results in excellent agreement with full quantum calculations. As such, the resulting method emerges as an attractive solution for the affordable modeling of strong light--matter coupling phenomena involving macroscopic numbers of optical modes.