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TT: Fachverband Tiefe Temperaturen

TT 43: Superconducting Electronics: Qubits

TT 43.2: Vortrag

Mittwoch, 11. März 2026, 09:45–10:00, CHE/0089

Observation of two-level systems in superconducting titanium-aluminum-nitride films — •Marius Frohn^1,2, Florian Mezger¹, Maximilian Kristen¹, Jan Nicolas Voss¹, Hannes Rotzinger^1,2, and Alexey Ustinov^1,2 — ¹Physikalisches Institut (PHI), Karlsruhe Institute for Technology (KIT), Germany — ²Institute for Quantum Materials and Technologies (IQMT), Karlsruhe Institute for Technology (KIT), Germany

Thin films of disordered superconductors are currently the subject of extensive study due to their potential applications in modern quantum circuits and kinetic inductance detectors. While many materials are possible candidates, those with low microwave loss and a high degree of disorder are especially interesting for high impedance circuits. The disordered microscopic structure also favors the presence of intrinsic material defects, some of which behave as two-level systems (TLS)[1]. Found in dielectrics such as surface oxides or tunneling barriers, TLS are a significant source of electromagnetic loss, which limits the coherence of superconducting qubits. It has been recently proposed [2], that applied direct-currents in the disordered superconductors are influencing the observable TLS coupling, e.g. to a microwave resonator. We present microwave spectroscopy measurements of ultra-compact, high impedance resonators made from titanium-aluminium-nitride films. By applying electric fields, we observe TLS strongly interacting with the resonator modes.
[1] M. Kristen et al., Phys. Rev. Lett. 132, 217002 (2024)
[2] T. Liu et al., Phys. Rev. B 111, L180502 (2025)

Keywords: superconducting quantum circuits; two-level systems; electric field spectroscopy; high impedance circuits; qubits