Microwave-to-optical quantum transducers will enable coherent interconnection between distant superconducting quantum devices. Ongoing explorations have shown promising results at single-photon levels. However, eliminating noise arising from the concurrence of weak transduced signals with intense pump pulses remains a challenge, requiring high-suppression filtering. Memory-assisted transduction offers a versatile noise-mitigation approach and enables on-demand retrieval of transduced signals. Here, we integrate a quantum memory protocol with transduction in a three-level atomic system. Leveraging zero-first-order Zeeman transitions at zero magnetic field, providing long optical and spin coherence times, and GHz-range hyperfine splitting, we use a low-doping concentration 171Yb3+:Y2SiO5 crystal at 30 mK. We achieve on-demand memory-assisted transduction with 0.4 (and 0.3) noise photons at a storage duration of 460 (and 620) μs. Further, we establish coherence via interference patterns and demonstrate multimode capacity, utilizing spin and optical inhomogeneous broadening. The on-demand retrieval enables qubit synchronization in quantum repeaters, while multimode capacity boosts entanglement generation rates. Current demonstrations of microwave-to-optical transduction suffer from noise due to the pump field. Here, the authors demonstrate memory-assisted microwave-to-optical transduction to avoid noise in a Yb:YSO crystal at 30 mK with zero B-field and multimode functionality.

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Nature

Researchers demonstrate a memory-assisted approach to microwave-to-optical quantum transduction using a low-doping 171Yb3+:Y2SiO5 crystal cooled to 30 mK at zero magnetic field. By integrating a quantum memory protocol with the transduction process, they suppress noise from the pump field, achieving as few as 0.3-0.4 noise photons at storage durations of 460-620 microseconds. The system also shows multimode capacity, which could boost entanglement generation rates for quantum repeater networks linking superconducting quantum devices via optical channels.

Memory-assisted multimode microwave-to-optical transduction