Fully Directional Quantum-limited Phase-Preserving Amplifier

TL;DR

This paper introduces a fully directional, quantum-limited phase-preserving amplifier using a superconducting Josephson circuit, achieving high reverse isolation and minimal back-action, suitable for scalable quantum computing systems.

Contribution

It demonstrates a novel four-mode superconducting circuit that achieves full directionality and quantum-limited amplification through interference of parametric processes.

Findings

Achieves reverse isolation surpassing forward gain.

Maintains minimal back-action unaffected by output port noise.

Enables on-chip integration with quantum processors.

Abstract

We present a way to achieve fully directional, quantum-limited phase-preserving amplification in a four-port, four-mode superconducting Josephson circuit by utilizing interference between six parametric processes that couple all four modes. Full directionality, defined as the reverse isolation surpassing forward gain between the matched input and output ports of the amplifier, ensures its robustness against impedance mismatch that might be present at its output port during applications. Unlike existing directional phase-preserving amplifiers, both the minimal back-action and the quantum-limited added noise of this amplifier remains unaffected by noise incident on its output port. In addition, the matched input and output ports allow direct on-chip integration of these amplifiers with other circuit QED components, facilitating scaling up of superconducting quantum processors.