SKM 2023 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 49: Quantum Coherence and Quantum Information Systems I

TT 49.3: Vortrag

Donnerstag, 30. März 2023, 12:00–12:15, HSZ 304

Showcasing the effective direct interaction between a readout resonator and a strongly coupled junction defect mediated by a transmon qubit — •Alexander K. Händel, Alexander Bilmes, Alexey V. Ustinov, and Jürgen Lisenfeld — Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany

Decoherence from material defects constitutes a principal problem on the way to improve superconducting quantum bits. Strongly coupled defects residing in the Josephson junction pose a particular challenge, demonstrating coupling strengths of multiple MHz. This strong coupling leads to avoided level crossings when qubit and defect come into resonance, and spoils qubit performance. In this work, we reveal an additional decoherence channel that occurs due to the resonant interaction between defects in the qubit's Josephson junction with the qubit's readout resonator, through an interaction mediated by the qubit. We investigate this effect using multi-photon spectroscopy and QuTiP simulations of the tripartite energy level spectrum.