Pinshane Y. Huang

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

  1. Oliver F. Wolff,
  2. Harshvardhan Mantry,
  3. Rahim Raja,
  4. Wei-Hsiang Peng,
  5. Kaushik Singirikonda,
  6. Seungkyun Lee,
  7. Shishir Sudhaman,
  8. Rafael Goncalves,
  9. Pinshane Y. Huang,
  10. Angela Kou,
  11. and Wolfgang Pfaff
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.
arxiv pdf