High-Purity Entanglement of Hot Propagating Modes Using Nonreciprocity

TL;DR

This paper demonstrates that nonreciprocity can be used to generate high-purity entangled propagating modes resilient to thermal noise, advancing quantum communication technologies.

Contribution

It introduces a method to use nonreciprocity and engineered reservoirs to produce robust, high-purity entanglement in propagating modes, suitable for circuit QED.

Findings

High-purity entanglement achieved despite thermal fluctuations

Nonreciprocity enables thermal fluctuation rerouting

Applicable to parametric circuit QED implementations

Abstract

Distributed quantum information processing and communication protocols demand the ability to generate entanglement among propagating modes. However, thermal fluctuations can severely limit the fidelity and purity of propagating entangled states, especially for low-frequency modes relevant for radio-frequency (RF) signals. Here we propose nonreciprocity as a resource to render continuous-variable entanglement of propagating modes robust against thermal fluctuations. By utilising a cold-engineered reservoir we break the symmetry of reciprocity in a standard two-mode squeezing interaction between a low- and a high-frequency mode, and show that the rerouting of thermal fluctuations allows the generation of flying entangled states with high purity. Our approach requires only pairwise Gaussian interactions and is thus ideal for parametric circuit QED implementations.