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arXiv · 2605.02755

Readout failures in superconducting qubits due to TLS-defects in tunnel junctions

J. Lisenfeld·A. K. Händel·A. Bilmes·A. V. Ustinov
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Abstract

Material defects give rise to parasitic two-level systems (TLS) which present a major source of decoherence in superconducting qubits. Here, we study a strongly coupled TLS that resides in the tunnel barrier of transmon qubit. We use multi-photon spectroscopy and TLS strain tuning to explore the rich spectrum of the interacting three-partite system consisting of TLS, qubit, and its readout resonator. This reveals a strong effective resonant coupling between the TLS and the qubit's readout resonator which dresses the resonator states and results in a resonance frequency shift that spoils the readout signal. Our finding presents yet another way how material defects can interfere with qubit operation and hinder the realization of solid-state quantum processors.

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J. Lisenfeld, A. K. Händel, A. Bilmes, A. V. Ustinov. 2026-05-04. Readout failures in superconducting qubits due to TLS-defects in tunnel junctions. https://doi.org/10.1103/ypm5-lh8d

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