Memory-assisted microwave-to-optical transduction*

Microwave-to-optical quantum transducers will enable coherent interconnection between future superconducting quantum devices. Several platforms have shown promising results reaching the single-photon levels with good device metrics. In all these platforms, the transduced signal comes out with the intense pump fields and therefore require high suppression filtering setups. Rare-earth ions doped in crystals is a leading candidate for quantum transduction application. Yb³⁺ ions doped in YSO crystal demonstrate large hyperfine splittings at zero magnetic field and provide long coherence times. Here, we use a three-level system in Yb:YSO to demonstrate storage of coherent microwave pulses and their on-demand transduction to optical mode. The on-demand transduction is beneficial for synchronizing qubit transfer between quantum devices. Even with no filtering involved, we achieve < 0.5 (0.2) noisy photons in the detection window at a storage time of 460 (700) μs. To prove coherent information transfer, we show interference patterns in transduced optical mode due to two phase- or frequency-different microwave modes. We also show spectro-temporal multi-mode capacity utilizing the spin and optical inhomogeneous broadening in Yb:YSO. Our result is the first demonstration of a microwave-to-optical transducer assisted by memory.