In-situ bandaged Josephson junctions for superconducting quantum processors

TL;DR

This paper introduces an improved shadow evaporation method for fabricating Josephson junctions with integrated bandage layers in a single step, reducing contamination and aging effects in superconducting quantum processors.

Contribution

The authors develop a novel in-situ fabrication technique that combines junction and bandage layer creation, simplifying process and enhancing junction stability.

Findings

Single-step fabrication reduces contamination.

Oxidation in oxygen atmosphere decreases junction aging.

Method improves junction quality for quantum computing.

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 oxidized in an oxygen atmosphere directly after deposition.