In-situ bandaged Josephson junctions for superconducting quantum processors
Alexander Bilmes (Karlsruhe Institut für Technologie)
Alexander K. Händel (Karlsruhe Institut für Technologie)
S. Volosheniuk (TU Delft - QN/van der Zant Lab, Kavli institute of nanoscience Delft)
Alexey V. Ustinov (Karlsruhe Institut für Technologie, Russian Quantum Center, Moscow, National University of Science and Technology MISiS)
Jürgen Lisenfeld (Karlsruhe Institut für Technologie)
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Abstract
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.
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