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arXiv · 2602.11469

Structural control of two-level defect density revealed by high-throughput correlative measurements of Josephson junctions

Oliver F. Wolff·Harshvardhan Mantry·Rahim Raja·Wei-Hsiang Peng·Kaushik Singirikonda·Seungkyun Lee·Shishir Sudhaman·Rafael Goncalves·Pinshane Y. Huang·Angela Kou·Wolfgang Pfaff
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Abstract

Materials defects in Josephson junctions (JJs), often referred to as two-level systems (TLS), couple to superconducting qubits and are a critical bottleneck for scalable quantum processors. Despite their importance, understanding the microscopic sources of TLS and how to mitigate them has remained a major challenge. Here, we demonstrate a high-throughput, correlated approach to trace the microstructural origins of strongly-coupled TLS in Josephson circuits. We assembled a massive dataset of TLS across 6,000 Al/AlOx/Al JJs and more than 600 atomic resolution transmission electron microscopy images. We statistically link fabrication, microstructure, and TLS occurrence, revealing a strong correlation between Al electrode thickness, Al grain size, and TLS density. Correspondingly, we find a two-thirds reduction in TLS prompted by a change in electrode fabrication parameters. These results demonstrate a robust, data-driven methodology to understand and control defects in quantum circuits and pave the way for significantly reducing TLS density.

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Oliver F. Wolff, Harshvardhan Mantry, Rahim Raja, Wei-Hsiang Peng, Kaushik Singirikonda, Seungkyun Lee, Shishir Sudhaman, Rafael Goncalves, Pinshane Y. Huang, Angela Kou, Wolfgang Pfaff. 2026-02-12. Structural control of two-level defect density revealed by high-throughput correlative measurements of Josephson junctions. https://arxiv.org/abs/2602.11469

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