High-efficiency coherent microwave-to-optics conversion via off-resonant scattering

Quantum transducers that can convert quantum signals from the microwave to the optical domain are a crucial optical interface for quantum information technology. Coherent microwave-to-optics conversions have been realized with various physical platforms, but all of them are limited to low efficiencies of less than 50%—the threshold of the no-cloning quantum regime. Here we report coherent microwave-to-optics transduction using Rydberg atoms and off-resonant scattering technique with an efficiency of 82 ± 2% and a bandwidth of about 1 MHz. The high conversion efficiency is maintained for microwave photons ranging from thousands to about 50, suggesting that our transduction is readily applicable to the single-photon level. Without requiring cavities or aggressive cooling for the quantum ground states, our results would push atomic transducers closer to practical applications in quantum technologies.