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TT: Fachverband Tiefe Temperaturen
TT 55: Superconducting Electronics: SQUIDs, Qubits, Circuit QED III
TT 55.8: Vortrag
Freitag, 21. März 2025, 11:30–11:45, H36
Higher Josephson harmonics in superconducting qubits — •Abbas H. Hirkani1,2, Giampiero Marchegiani1, Luigi Amico1,3,4, and Gianluigi Catelani1,5 — 1QRC, TII, Abu Dhabi, UAE — 2SISSA, Trieste, Italy — 3Dipartimento di Fisica e Astronomia, Catania, Italy — 4INFN-Catania, Catania, Italy — 5Forschungszentrum Jülich, Jülich, Germany
Measurements of higher-level spectra of transmon cannot be explained using the standard I=I0sinφ current-phase relation, and a more accurate description of the Josephson element, with non-negligible contributions from higher harmonics, is needed [1]. Stray inductances can also lead to similar corrections to the spectrum; here we investigate the Fraunhofer effect in transmons comprising thin-film Al/AlOx/Al junctions under parallel magnetic field [2] as a tool to discriminate between contributions from inductances and from intrinsic higher harmonics of the junctions. The magnetic field modulates each harmonic on a different field scale; this results in a field dependence of the qubit spectrum measurably different from the one due to a stray inductance alone. We also examine how the presence of a few percent higher harmonic contributions affects various qubit designs, and comment on the implications for accurate targeting of qubit parameters.
[1] D. Willsch et al., Nat. Phys. 20, 815 (2024);
[2] J. Krause et al., Phys. Rev. App. 22, 044063 (2024).
Keywords: Josephson Junctions; Superconducting circuits; Superconducting qubits; Circuit QED