Flux noise without flux tunability in superconducting qubits
Abstract
Flux noise is unanimously recognised as a leading dephasing mechanism for flux-tunable superconducting qubits. However, our microscopic understanding remains incomplete, and basic effects like Faraday's law of induction have only very recently come into focus. Based on a quantum geometric description of the Faraday effect, we provide an in-depth derivation of the coupling of generic magnetic sources to thin film superconducting structures, under appropriate consideration of the device geometry. We apply the resulting framework to time-varying magnetic dipoles, describing surface or substrate spins, as well as current-carrying flux lines. We show that flux noise not only affects dephasing, but also provides a fundamental limit for the qubit quality factor - notably, even when the qubit contains no loops and is thus nominally not flux-tunable. Assuming surface spins as the origin for universal flux noise, we expect that this quality factor limit might be reached in the near term. For flux lines, we formulate a minimal safety distance to conserve the qubit performance, potentially constraining the scale-up of quantum hardware. This distance is boosted in the presence of large capacitor wings typical for transmons, due to a lensing of the electromotive field which is largely independent of Meissner screening.
Related
- Tunable, modeless, and hybridization-free cross-Kerr coupler for miniaturized superconducting qubits
- Modeling Logical Gates and Readout of Superconducting Gottesman-Kitaev-Preskill Qubits
- Towards fault-tolerant quantum computing with optically controlled superconducting qubits
- Characterization of Radiation-Induced Errors in Superconducting Qubits Protected with Various Gap-Engineering Strategies
- Readout failures in superconducting qubits due to TLS-defects in tunnel junctions
BibTeX
@misc{kruti2026flux,
title = {{Flux noise without flux tunability in superconducting qubits}},
author = {Daniel Kruti and Roman-Pascal Riwar},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.03059},
eprint = {2609.03059},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.03059},
}
RIS
TY - UNPB
TI - Flux noise without flux tunability in superconducting qubits
AU - Daniel Kruti
AU - Roman-Pascal Riwar
PY - 2026
DA - 2026/09/02
PB - arXiv
DO - 10.48550/arxiv.2609.03059
UR - https://arxiv.org/abs/2609.03059
AB - Flux noise is unanimously recognised as a leading dephasing mechanism for flux-tunable superconducting qubits. However, our microscopic understanding remains incomplete, and basic effects like Faraday's law of induction have only very recently come into focus. Based on a quantum geometric description of the Faraday effect, we provide an in-depth derivation of the coupling of generic magnetic sources to thin film superconducting structures, under appropriate consideration of the device geometry. We apply the resulting framework to time-varying magnetic dipoles, describing surface or substrate spins, as well as current-carrying flux lines. We show that flux noise not only affects dephasing, but also provides a fundamental limit for the qubit quality factor - notably, even when the qubit contains no loops and is thus nominally not flux-tunable. Assuming surface spins as the origin for universal flux noise, we expect that this quality factor limit might be reached in the near term. For flux lines, we formulate a minimal safety distance to conserve the qubit performance, potentially constraining the scale-up of quantum hardware. This distance is boosted in the presence of large capacitor wings typical for transmons, due to a lensing of the electromotive field which is largely independent of Meissner screening.
ER -