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.
@article{arxiv.2302.12280,
title = {Characterization of Asymmetric Gap-Engineered Josephson Junctions and 3D Transmon Qubits},
author = {Zach Steffen and S. K. Dutta and Haozhi Wang and Kungang Li and Yizhou Huang and Yi-Hsiang Huang and Advait Mathur and F. C. Wellstood and B. S. Palmer},
journal= {arXiv preprint arXiv:2302.12280},
year = {2023}
}
Comments
5 pages, 3 figures, to be published in IEEE Transactions on Applied Superconductivity