Andre Vallieres

Enhanced Superconducting Qubit Performance Through Ammonium Fluoride Etch

  1. Cameron J. Kopas,
  2. Dominic P. Goronzy,
  3. Thang Pham,
  4. Carlos G. Torres-Castanedo,
  5. Matthew Cheng,
  6. Rory Cochrane,
  7. Patrick Nast,
  8. Ella Lachman,
  9. Nikolay Z. Zhelev,
  10. Andre Vallieres,
  11. Akshay A. Murthy,
  12. Jin-su Oh,
  13. Lin Zhou,
  14. Matthew J. Kramer,
  15. Hilal Cansizoglu,
  16. Michael J. Bedzyk,
  17. Vinayak P. Dravid,
  18. Alexander Romanenko,
  19. Anna Grassellino,
  20. Josh Y. Mutus,
  21. Mark C. Hersam,
  22. and Kameshwar Yadavalli
The performance of superconducting qubits is often limited by dissipation and two-level systems (TLS) losses. The dominant sources of these losses are believed to originate from amorphous
materials and defects at interfaces and surfaces, likely as a result of fabrication processes or ambient exposure. Here, we explore a novel wet chemical surface treatment at the Josephson junction-substrate and the substrate-air interfaces by replacing a buffered oxide etch (BOE) cleaning process with one that uses hydrofluoric acid followed by aqueous ammonium fluoride. We show that the ammonium fluoride etch process results in a statistically significant improvement in median T1 by ∼22% (p=0.002), and a reduction in the number of strongly-coupled TLS in the tunable frequency range. Microwave resonator measurements on samples treated with the ammonium fluoride etch prior to niobium deposition also show ∼33% lower TLS-induced loss tangent compared to the BOE treated samples. As the chemical treatment primarily modifies the Josephson junction-substrate interface and substrate-air interface, we perform targeted chemical and structural characterizations to examine materials‘ differences at these interfaces and identify multiple microscopic changes that could contribute to decreased TLS.
arxiv pdf