Overlap junctions for superconducting quantum electronics and amplifiers

TL;DR

This paper extends the fabrication process of overlap Josephson junctions to micrometer scales, enabling the creation of high-performance superconducting quantum devices like tunable amplifiers with minimal infrastructure.

Contribution

It introduces a scalable, efficient fabrication method for overlap Josephson junctions suitable for various superconducting quantum devices.

Findings

Demonstrated a micrometer-scale overlap junction process.

Fabricated a Josephson parametric amplifier with ~30 dB gain.

Achieved devices with negligible insertion loss and high yield.

Abstract

Due to their unique properties as lossless, nonlinear circuit elements, Josephson junctions lie at the heart of superconducting quantum information processing. Previously, we demonstrated a two-layer, submicrometer-scale overlap junction fabrication process suitable for qubits with long coherence times. Here, we extend the overlap junction fabrication process to micrometer-scale junctions. This allows us to fabricate other superconducting quantum devices. For example, we demonstrate an overlap-junction-based Josephson parametric amplifier that uses only 2 layers. This efficient fabrication process yields frequency-tunable devices with negligible insertion loss and a gain of ~ 30 dB. Compared to other processes, the overlap junction allows for fabrication with minimal infrastructure, high yield, and state-of-the-art device performance.