A Traveling Wave Parametric Amplifier Isolator

TL;DR

This paper presents a superconducting traveling-wave parametric amplifier isolator that achieves broadband, quantum-limited amplification with built-in reverse isolation, eliminating the need for bulky magnetic isolators.

Contribution

It introduces a Josephson-junction-based traveling-wave amplifier with integrated isolation using nonlinear frequency conversion and phase matching, enabling broadband, directional amplification.

Findings

Gain up to 20 dB achieved

Reverse isolation up to 30 dB demonstrated

Bandwidth greater than 500 MHz with near-quantum-limited noise

Abstract

Superconducting traveling-wave parametric amplifiers have emerged as highly promising devices for near-quantum-limited broadband amplification of microwave signals and are essential for high quantum-efficiency microwave readout lines. Built-in isolation, as well as gain, would address their primary limitation: lack of true directionality due to potential backward travel of electromagnetic radiation to their input port. Here, we demonstrate a Josephson-junction-based traveling-wave parametric amplifier isolator. It utilizes third-order nonlinearity for amplification and second-order nonlinearity for frequency upconversion of backward propagating modes to provide reverse isolation. These parametric processes, enhanced by a novel phase matching mechanism, exhibit gain of up to 20~dB and reverse isolation of up to 30~dB over a static 3~dB bandwidth greater than 500~MHz, while keeping near-quantum limited added noise. This demonstration of a broadband truly directional amplifier ultimately paves the way towards broadband quantum-limited microwave amplification lines without bulky magnetic isolators and with inhibited back-action.