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Superconducting Qubits Open Quantum Systems Decoherence Quantum Chemistry

textit{Ab initio} Identification of Hydrogen Tunneling as Two-Level Systems in Nb2O5 and Ta2O5

arXiv
Authors: Cristóbal Méndez, Tomás A. Arias

Year

2026

Paper ID

30654

Status

Preprint

Abstract Read

~2 min

Abstract Words

108

Citations

N/A

Abstract

Two-level systems (TLS) in native Nb and Ta oxides limit superconducting-qubit coherence and SRF-cavity quality factors in the microwave frequency range, yet their microscopic origin remains unclear. We combine MLIP-accelerated sampling of hydrogen configurations and diffusion pathways in amorphous Nb and Ta pentoxides with targeted textit{ab initio} validation. Hydrogen is the only light interstitial with barrier-distance combinations near the sim0.1-10 GHz tunneling regime, and its ensemble statistics in amorphous oxides produce effective TLS densities and loss estimates consistent with the experimentally observed higher loss in Nb oxide than in Ta oxide. Our results point to H tunneling as a plausible microscopic TLS source in these materials.

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  • Two-level systems (TLS) in native Nb and Ta oxides limit superconducting-qubit coherence and SRF-cavity quality factors in the microwave frequency range, yet their microscopic...

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References & Citation Signals

[1] DOI https://doi.org/arXiv:2603.17194 [2] arXiv https://arxiv.org/abs/2603.17194 [3] Publisher https://arxiv.org/abs/2603.17194

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