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TT: Fachverband Tiefe Temperaturen

TT 22: Superconductivity – Poster I

TT 22.19: Poster

Montag, 9. März 2026, 18:00–20:00, P1

Landau-Zener transitions in ultra-cold glasses — •Jan Blickberndt, Christian Ständer, Anton Jarecka, Andreas Fleischmann, Andreas Reiser, and Christian Enss — Kirchhoff-Institute for Physics, Heidelberg University, Germany

Atomic tunneling systems (TSs) are inherent to disordered structures and therefore appear not only in amorphous solids, but also in oxide layers, tunneling barriers and interfaces of superconducting micro-structured devices, deteriorating their performance by introducing noise and decoherence. Understanding their nature is thus crucial to mitigate the adverse effects of TSs on quantum devices. In this work we investigate the non-equilibrium dynamics of a resonantly driven TS ensemble, which is influenced by slowly varying electric or mechanical bias fields by tuning the TSs energy splitting. To directly probe the TSs dielectric response, we developed a superconducting lumped element resonator microfabricated onto a bulk glass substrate, enabling controlled excitation and readout of the underlying TS population. By varying the sweep rate of the applied bias, we demonstrate rate-dependent control over the dielectric loss of the sample. Furthermore, when applying sufficiently large bias amplitudes we observe a dispersive red shift of the resonator frequency due to an excess saturation of low-energy TSs. Introducing noise bias fields leads to a measurable reduction of effective TS coherence times, demonstrating their sensitivity to spectral fluctuations in their environment. To complement our experiments, we developed a GPU-accelerated Monte Carlo simulation of the tunneling dynamics to validate and extend our findings.

Keywords: atomic tunneling systems; amorphous dielectrics; microwave resonators; Landau-Zener dynamics; dielectric loss