Giant microwave-optical Kerr nonlinearity via Rydberg excitons in cuprous oxide [dataset]

Microwave-optical conversion is key to future networks of quantum devices, such as those based on superconducting technology. Conversion at the single quantum level requires strong nonlinearity, high bandwidth, and compatibility with a millikelvin environment. A large nonlinearity is observed in Rydberg atoms, but combining atomic gases with dilution refrigerators is technically challenging. Here we demonstrate that a strong microwave-optical nonlinearity in a cryogenic, solid-state system by exploiting Rydberg states of excitons in \cuprite. We measure a microwave-optical cross-Kerr coefficient of B0=0.022±0.008 m V−2 at 4~K, which is several orders of magnitude larger than other solid-state systems. Our results highlight the potential of Rydberg excitons for nonlinear optics, and form the basis for a microwave-optical frequency converter based on Cu2O.

微波-光转换是未来基于超导技术等量子器件网络的核心关键技术。实现单量子级别的转换需具备强非线性、高带宽特性，且需兼容毫开尔文级低温环境。里德伯原子（Rydberg atom）中可观测到极强的非线性效应，但将原子气体与稀释制冷机结合在技术上颇具挑战。本研究通过利用赤铜矿（cuprite）中激子的里德伯态，在低温固态系统中实现了强微波-光非线性效应。我们在4开尔文温度下测得微波-光交叉克尔系数为B₀=0.022±0.008 mV⁻²，该数值较其他固态系统高出数个数量级。本研究证实了里德伯激子在非线性光学领域的应用潜力，同时为基于氧化亚铜（Cu₂O）的微波-光频率转换器奠定了研究基础。