Quantum-memory-assisted on-demand microwave-optical transduction.

Tu, Hai-Tao; Liao, Kai-Yu; Qiu, Si-Yuan; Liu, Xiao-Hong; Guo, Yi-Qi; Du, Zheng-Qi; Xu, Yang; Zhang, Xin-Ding et al. · Nat Commun · 2026

basic_science · Level V

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Abstract

Microwave-optical transducers and quantum memories are essential for quantum repeaters enabling a quantum internet. Despite advances in both technologies, integrating these functionalities remains challenging. Here, we theoretically propose and experimentally demonstrate an on-demand microwave-optical quantum transducer based on a Rydberg ensemble. Using cascaded electromagnetically induced transparency, we store microwave photons in a highly excited collective state and convert them into optical photons during retrieval. Leveraging an optical depth of millions for microwave photons and minimal single-photon-level dephasing, our transducer achieves around 90% area-normalized storage efficiency, 2.3 MHz bandwidth, and noise-equivalent temperature of 26 K under cavity-free conditions. Furthermore, our system is cryogenically compatible and extendable for high single-photon conversion efficiency without requiring optical cavity coupling. These findings advance practical on-demand quantum interfaces with broad applications across atomic and solid-state platforms.