Mainz 2026 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 9: Open Quantum Systems and Spin-Boson Systems I

Q 9.7: Vortrag

Montag, 2. März 2026, 18:30–18:45, P 4

Observing time-dependent energy level renormalization in an ultrastrongly coupled open system — •Florian Hasse, Frederike Doerr, Tobias Spanke, Deviprasath Palani, Ulrich Warring, Alessandra Colla, Heinz-Peter Breuer, and Tobias Schaetz — Institute of Physics, University of Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg, Germany

Understanding how strong coupling and memory effects influence energy levels in open quantum systems is a fundamental challenge. Here, we experimentally probe these effects in a two-level open system coupled to a single-mode quantum environment, using Ramsey interferometry in a trapped ion. Operating in the strong coupling regime, we observe both dissipative effects and time-dependent energy shifts of up to 15% of the bare system frequency, with the total system effectively isolated from external environments [1]. These dynamic shifts, likely ubiquitous across quantum platforms, arise solely from ultra-strong system-mode interactions and correlation build-up and are accurately predicted by the minimal-dissipation Ansatz [2]. Our approach identifies these as generalised Lamb shifts, matching conventional predictions on time-average. We provide experimental fingerprints supporting the Ansatz of minimal-dissipation, thereby suggesting it as a testable quantum thermodynamics framework and establishing a foundation for future benchmarks in strong-coupling quantum thermodynamics and related technologies.

[1] Colla, A., Hasse, F., et al., Nat. Commun. 16, 2502 (2025).

[2] Colla, A. and Breuer, H.-P., Phys. Rev. A 105, 052216 (2022)

Keywords: Quantum Thermodynamics; Non-Markovianity; Ultra-Strong Coupling Regime; Minimal-Dissipation Ansatz; Ramsey Interferometry