Regensburg 2025 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 50: Superconducting Electronics: SQUIDs, Qubits, Circuit QED II

TT 50.8: Vortrag

Donnerstag, 20. März 2025, 17:00–17:15, H36

Gauging away 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 no photons. Thus only this gauge fits the intuitive understanding that the cavity should be empty in the lowest energy state even for strong light-matter interaction.
[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