Long-lived transmons with different electrode layouts

IQC Seminar - Kungang Li, University of Maryland

In the realm of quantum computing,non-equilibrium quasiparticle tunneling may be a significant loss mechanism in transmon qubits. Understanding the behavior of these quasiparticles across junctions may lead to improved qubit devices . One approach involves the fabrication of asymmetric transmons through gap-engineering techniques aimed at mitigating quasiparticle tunneling and subsequent loss. In our research, we have conducted repeated measurements of the relaxation time (T1) in Al/AlOx/Al transmons featuring electrodes with varying superconducting gap values. Specifically, one device utilized a first-layer electrode formed via thermal evaporation of nominally pure Al, while the counter-electrode incorporated oxygen-doped Al. This device exhibited notable fluctuations in T1, ranging from approximately 100 μs to slightly over 300 μs at 20 mK. Additionally, we explored different configurations of junction layouts in an effort to enhance device performance.

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