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THU: Thursday Contributed Sessions

THU 10: Foundational / Mathematical Aspects – Methods and Approximations

THU 10.6: Talk

Thursday, September 11, 2025, 15:30–15:45, ZHG103

Approximations in light-matter interaction — •Leonhard Richter, Daniel Burgarth, and Davide Lonigro — Department Physik FAU Erlangen-Nürnberg, Staudtstr. 7, 91058 Erlangen

I will present recent advances in quantifying the quality of approximations such as the rotating-wave approximation. Specifically, I present bounds on the norm difference between the unitary evolutions generated by the full Hamiltonian and the approximation applied to the same initial state. As full-quantum models of light-matter interaction are unbounded in energy, the derived error bounds depend on the particular initial state of the system and convergence is only given in the strong and not in the uniform sense. The central method enabling such derivation in these settings is based on repeated integration-by-parts of the difference of two unitary evolutions.

Keywords: Rotating-wave approximation; Light-matter interaction; Error bounds; High-frequency limit