Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 55: Superconducting Electronics: SQUIDs, Qubits, Circuit QED III

TT 55.3: Talk

Friday, March 21, 2025, 10:00–10:15, H36

Simultaneous locking and operation of gradiometric fluxonium qubits — •Denis Bénâtre¹, Mathieu Féchant¹, Nicolas Gosling¹, Nicolas Zapata¹, Patrick Paluch¹, Martin Spiecker¹, and Ioan Pop^1,2,3 — ¹IQMT, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany — ²PHI, Karlsruhe Institute of Technology, Karlsruhe, Germany — ³PI1, Stuttgart University, 70569 Stuttgart, Germany

Gradiometric fluxoniums, introduced by Gusenkova et al. (Appl. Phys. Lett. 120, 2022), have the ability to be flux-locked at the sweet spot of operation by trapping a persistent current in their most external loop. We demonstrate the reliability of the procedure by simultaneously locking several fluxoniums sitting in the same waveguide and show that the locking in stable in time. We engineer devices with varying asymmetries and exhibit samples with close-to-zero asymmetry, allowing them to be used with little additional flux-biasing. Such devices could thus help reduce cross-talk between flux lines addressing flux qubits.

Keywords: Fluxonium; cQED; Superconductivity; Qubit; Granular aluminum