Optimizing the pump coupling for a three-wave mixing Josephson parametric amplifier

TL;DR

This paper presents an optimized pump coupling scheme for a three-wave mixing Josephson parametric amplifier using microwave filtering, significantly improving power efficiency and reducing pump leakage while maintaining high performance.

Contribution

It introduces a microwave filter-based pump coupling method for JPAs, achieving over three orders of magnitude improvements in efficiency and leakage suppression compared to traditional methods.

Findings

Over three orders of magnitude improvement in power efficiency.

Significant reduction in pump leakage.

Maintains state-of-the-art noise performance and robustness against pump noise.

Abstract

Josephson element-based parametric amplifiers (JPAs) typically require rf pump power that is several orders of magnitude stronger than the maximum signal power they can handle. The low power efficiency and strong pump leakage towards signal circuitry could be critical concerns in application. In this work, we discuss how to optimize the pump coupling scheme for a three-wave mixing JPA by employing microwave filtering techniques, with the goal of maximizing the pump power efficiency and minimize pump leakage without sacrificing other properties of interest. We implement the corresponding filter design in a SNAIL-based JPA and demonstrate more than three orders of magnitude improvement in both power efficiency and pump leakage suppression compared to a similar device with regular capacitive coupling, while maintaining state-of-the-art dynamic range and near-quantum-limited noise performance. Furthermore, we show experimentally that the filter-coupled JPA is more robust against noise input from the pump port, exhibiting no significant change in added noise performance with up to 4 K of effective noise temperature at the pump port.