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arXiv · 2302.12280

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

Zach Steffen·S. K. Dutta·Haozhi Wang·Kungang Li·Yizhou Huang·Yi-Hsiang Huang·Advait Mathur·F. C. Wellstood·B. S. Palmer
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Abstract

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.

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Zach Steffen, S. K. Dutta, Haozhi Wang, Kungang Li, Yizhou Huang, Yi-Hsiang Huang, Advait Mathur, F. C. Wellstood, B. S. Palmer. 2023-02-23. Characterization of Asymmetric Gap-Engineered Josephson Junctions and 3D Transmon Qubits. https://doi.org/10.1109/tasc.2023.3247987

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