Device variability of Josephson junctions induced by interface roughness

• URL: http://arxiv.org/abs/2602.03037v1
• Date: Tue, 03 Feb 2026 03:03:43 GMT
• Title: Device variability of Josephson junctions induced by interface roughness
• Abstract summary: Superconducting qubits are commonly realized using Al/AlO$_textx$/Al Josephson junctions.<n>We develop a model for the variability of the Josephson energy $E_J$ induced by interface roughness at the Al/AlO$_textx$ interfaces.
• Score: 4.352963819223116
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: As quantum processors scale to large qubit numbers, device-to-device variability emerges as a critical challenge. Superconducting qubits are commonly realized using Al/AlO$_{\text{x}}$/Al Josephson junctions operating in the tunneling regime, where even minor variations in device geometry can lead to substantial performance fluctuations. In this work, we develop a quantitative model for the variability of the Josephson energy $E_{J}$ induced by interface roughness at the Al/AlO$_{\text{x}}$ interfaces. The roughness is modeled as a Gaussian random field characterized by two parameters: the root-mean-square roughness amplitude $σ$ and the transverse correlation length $ξ$. These parameters are extracted from the literature and molecular dynamics simulations. Quantum transport is treated using the Ambegaokar--Baratoff relation combined with a local thickness approximation. Numerical simulations over $5,000$ Josephson junctions show that $E_{J}$ follows a log-normal distribution. The mean value of $E_{J}$ increases with $σ$ and decreases slightly with $ξ$, while the variance of $E_{J}$ increases with both $σ$ and $ξ$. These results paint a quantitative and intuitive picture of Josephson energy variability induced by surface roughness, with direct relevance for junction design.

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