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 utilizing 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.
Bibliographical noteFunding Information:
We thank C. M. Wilson and C. W. Sandbo Chang for the useful discussions. A.M. and L.O. acknowledge funding by the Deutsche Forschungsgemeinschaft through the project CRC 910 and the Emmy Noether program (Grant No. ME 4863/1-1). S.K. acknowledges funding by the Israeli Science Foundation (Grant No. 1794/21) and the Israeli Innovation Authority (Grant No. 73754). We acknowledge support by the KIT-Publication Fund of the Karlsruhe Institute of Technology.
© 2023 authors. Published by the American Physical Society.