Quantum 2025 – wissenschaftliches Programm

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THU: Thursday Contributed Sessions

THU 13: Poster Session: Applications

THU 13.80: Poster

Donnerstag, 11. September 2025, 16:30–18:30, ZHG Foyer 1. OG

Gauging the ground-state photon content of the Quantum Rabi model — •Arka Dutta, Daniel Braak, and Marcus Kollar — Theoretische Physik III, University of Augsburg

The quantum Rabi model (QRM) features the simplest type of coupling between a single cavity light mode and an atomic electron. It is integrable if the electronic degree of freedom is truncated to just two states [1]. The derivation of the effective Hamiltonian leads to different forms depending on the chosen gauge [2]. In the dipole gauge, the ground state of the QRM exhibits non-zero photon number in contrast to its weak coupling approximation, the Jaynes-Cummings model. We compute the exact photon content for all eigenstates in an arbitrary gauge and obtain a gauge for which the ground state contains a minimal number of photons. Conversely the ground state photon content determines the corresponding gauge of the Rabi model.
[1] D. Braak, Phys. Rev. Lett. 107, 100401 (2011).
[2] O. Di Stefano et al., Nat. Phys. 15, 803 (2019).

Keywords: Quantum Optics; Cavity QED; Gauge invariance; Rabi Model; Light matter interaction