Gain compression in Josephson Traveling-Wave Parametric Amplifiers

TL;DR

This paper experimentally investigates gain compression in Josephson traveling-wave parametric amplifiers, revealing that pump depletion and phase-matching processes both contribute to gain saturation, informing optimization for high-power applications.

Contribution

It provides the first comprehensive experimental analysis of gain compression mechanisms in Josephson TWPAs, including pump depletion and phase-matching effects.

Findings

Pump depletion occurs during gain compression.

Power-induced phase-matching contributes to gain saturation.

Insights aid in optimizing TWPAs for high-power applications.

Abstract

Superconducting traveling-wave parametric amplifiers (TWPAs) are increasingly used in various applications, including quantum computing, quantum sensing, and dark matter detection. However, one important characteristic of these amplifiers, gain compression, has not received much attention. As a result, there is a lack of comprehensive experimental exploration of this phenomenon in the existing literature. In this study, we present an experimental investigation of gain compression in a Josephson traveling-wave parametric amplifier based on a four-wave mixing process. We have implemented a novel setup to monitor the complex transmission of both the pump and signal tones, which allows us to simultaneously track pump depletion and signal amplification as functions of signal power and frequency across the entire bandwidth of the device. Our findings indicate that, while pump depletion occurs during gain compression, it is not the only mechanism involved in the saturation of a TWPA. Power-induced phase-matching processes also take place within the device. This study provides valuable insights for optimizing TWPAs for applications that require high total input power, such as multiplexed qubit readout or broadband photon emission.