Regensburg 2022 – scientific programme

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QI: Fachverband Quanteninformation

QI 13: Implementations: Superconducting Qubits

QI 13.12: Talk

Friday, September 9, 2022, 12:45–13:00, H8

In-situ bandaged Josephson junctions for superconducting quantum processors — •Alexander Bilmes¹, Alexander K. Händel¹, Serhii Volosheniuk², Alexey V. Ustinov¹, and Juergen Lisenfeld¹ — ¹Karlsruhe Institute of Technology (KIT), Wolfgang-Gaedestr. 1, 76131 Karlsruhe, Germany — ²Delft University of Technology, 2628 CJ Delft, Netherlands

Shadow evaporation is commonly used to micro-fabricate the key element of superconducting qubits--the Josephson junction. However, in conventional two-angle deposition circuit topology, unwanted stray Josephson junctions are created which contribute to dielectric loss. So far, this could be avoided by shorting the stray junctions with a so-called bandage layer deposited in an additional lithography step which may further contaminate the chip surface. Here, we present an improved shadow evaporation technique allowing one to fabricate sub-micrometer-sized Josephson junctions together with bandage layers in a single lithography step. We also show that junction aging is significantly reduced when junction electrodes are passivated in an oxygen atmosphere directly after deposition.