Impact of Oxygen Vacancies in Josephson Junction on Decoherence of Superconducting Qubits

• URL: http://arxiv.org/abs/2603.11469v1
• Date: Thu, 12 Mar 2026 02:47:22 GMT
• Title: Impact of Oxygen Vacancies in Josephson Junction on Decoherence of Superconducting Qubits
• Abstract summary: Amorphous Al$$O$_3$ is widely used as a barrier material, but under irradiation, oxygen vacancy (V$_O$) defects are readily generated.<n>We investigate the structural characteristics and electronic impact of V$_O$ defects in amorphous Al$$O$_3$ using first-principles calculations.<n>Our results show that both the coordination environment and concentration of V$_O$s strongly influence electrical conductivity.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Superconducting quantum circuits are promising platforms for scalable quantum computing, where qubit coherence is critically determined by microscopic defects in the oxide tunneling barrier of Josephson junctions. Amorphous Al$_2$O$_3$ is widely used as a barrier material, but under irradiation, oxygen vacancy (V$_O$) defects are readily generated, introducing noise sources that accelerate qubit decoherence. We systematically investigate the structural characteristics and electronic impact of V$_O$ defects in amorphous Al$_2$O$_3$ using first-principles calculations and \textit{ab initio} molecular dynamics. Our results show that both the coordination environment and concentration of V$_O$s strongly influence electrical conductivity. In particular, two- and three-coordinated V$_O$s, unique to the amorphous structure, enhance conductivity more than conventional four-coordinated vacancies. Increasing V$_O$ concentration amplifies conductivity fluctuations, which we link to critical current noise in Josephson junctions. Using a noise model, we estimate that higher V$_O$ densities lead to shorter qubit coherence times. These findings provide insights for radiation-hard design of superconducting quantum devices.

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