Quantum-coherent optical isolation and circulation using frequency conversion on a chip

TL;DR

This paper demonstrates a scalable, chip-integrated quantum optical isolator and circulator using frequency conversion, achieving high performance while preserving quantum coherence, enabling advanced quantum communication applications.

Contribution

It introduces a novel, integrated, nonmagnetic quantum optical nonreciprocity device based on frequency conversion, with high fidelity and tunability, advancing quantum photonic technology.

Findings

Achieved 34 dB isolation with low 0.8 dB insertion loss.

Maintained 97% operational fidelity and broad 44 GHz bandwidth.

Enabled scalable, on-chip quantum nonreciprocal photonic devices.

Abstract

Breaking optical reciprocity enables new regimes of light--matter interaction with broad implications for fundamental physics and emerging quantum technologies. Although various approaches have been explored to achieve optical nonreciprocity, realizing it at the single-photon level has remained a major challenge. Here, we demonstrate nonmagnetic optical nonreciprocity -- including both isolation and circulation -- in the quantum regime, enabled by efficient and noiseless all-optical frequency conversion on an integrated III-V photonic chip. Our device preserves the quantum coherence and entanglement of the input photons while delivering exceptional performance parameters, including a high extinction ratio of 34 dB, low insertion loss of 0.8 dB, broad bandwidth of 44 GHz, high operational fidelity of 97%, and widely tunable operation wavelength. This realization of quantum optical nonreciprocity in a scalable photonic platform opens a pathway toward directional quantum communication and noise-resilient quantum networks.