Dresden 2026 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 43: Superconducting Electronics: Qubits

TT 43.1: Vortrag

Mittwoch, 11. März 2026, 09:30–09:45, CHE/0089

Analysis of Flux Noise in Charge Qubits — •Daniel Kruti and Roman-Pascal Riwar — Peter Grünberg Institute, Theoretical Nanoelectronics, Jülich Research Centre, Jülich, D-52425, Germany & Cologne University

Improving the lifetime of quantum information stored in superconducting qubits is a focal point of contemporary research. However, the modelling of time-dependent flux noise has long been based on simplified lumped-element approaches, neglecting details of the device layout and flux distribution. Building on a recently developed quantum geometric description of Faraday's law of induction, we provide an in-depth analysis of charge qubit relaxation and decoherence rates for various flux noise sources, such as surface spins and the surrounding qubit control hardware. Contrary to standard circuit theory, our treatment reveals that a circuit does not require flux-tunability (e.g. a dc-SQUID) in order to be affected by flux noise, as flux-induced relaxation persists in the single junction limit. We link relaxation and dephasing by a geometry-dependent form factor, allowing experimental 1/f flux noise spectra to be used for quantitative estimates. These suggest that, while surface spins are likely negligible for current qubit performances, far-field flux sources due to the surrounding hardware can, in principle, contribute significantly.

Keywords: Time-dependent phase; Flux noise; Qubit; SQUID; Coherence