Cavity electro-optic circuit for microwave-to-optical conversion in the quantum ground state
Wei Fu, Mingrui Xu, Xianwen Liu, Chang‐Ling Zou, Changchun Zhong, Xu Han, Mohan Shen, Yuntao Xu, Risheng Cheng, Sihao Wang, Liang Jiang, Hong X. Tang
Abstract
In the development of microwave-to-optical (MO) quantum transducers, suppressing added noise induced by the optical excitation remains a major challenge. Here we report an integrated superconducting cavity electro-optic circuit based on single crystalline thin-film aluminum nitride of ultralow microwave and optical losses. We demonstrate efficient bi-directional MO conversion at milli-Kelvin temperatures, with near-ground state microwave thermal excitation $({\overline{n}}_{\mathrm{e}}=0.09\ifmmode\pm\else\textpm\fi{}0.06)$, despite the peak power of the optical drive exceeding the cooling power of the dilution refrigerator mixing chamber. Our dynamical study further reveals different light-induced noise generation mechanisms and provides crucial guidelines for optimizing electro-optic circuits in future hybrid microwave-optical quantum links.