Advait Mathur

Characterization of Asymmetric Gap-Engineered Josephson Junctions and 3D Transmon Qubits

  1. Zach Steffen,
  2. S. K. Dutta,
  3. Haozhi Wang,
  4. Kungang Li,
  5. Yizhou Huang,
  6. Yi-Hsiang Huang,
  7. Advait Mathur,
  8. F. C. Wellstood,
  9. and B. S. Palmer
We have fabricated and characterized asymmetric gap-engineered junctions and transmon devices. To create Josephson junctions with asymmetric gaps, Ti was used to proximitize and lower
the superconducting gap of the Al counter-electrode. DC IV measurements of these small, proximitized Josephson junctions show a reduced gap and larger excess current for voltage biases below the superconducting gap when compared to standard Al/AlOx/Al junctions. The energy relaxation time constant for an Al/AlOx/Al/Ti 3D transmon was T1 = 1 {\mu}s, over two orders of magnitude shorter than the measured T1 = 134 {\mu}s of a standard Al/AlOx/Al 3D transmon. Intentionally adding disorder between the Al and Ti layers reduces the proximity effect and subgap current while increasing the relaxation time to T1 = 32 {\mu}s.
arxiv pdf