Entangling microwave-frequency superconducting quantum processors through optical light at ambient temperature would enable means of secure communication and distributed quantum information processing¹. However, transducing quantum signals between these disparate regimes of the electro-magnetic spectrum remains an outstanding goal^{2,3,4,5,6,7,8,9}, and interfacing superconducting qubits, which are constrained to operate at millikelvin temperatures, with electro-optic transducers presents considerable challenges owing to the deleterious effects of optical photons on superconductors^9,10. Moreover, many remote entanglement protocols^11,12,13,14 require multiple qubit gates both preceding and following the upconversion of the quantum state, and thus an ideal transducer should impart minimal backaction¹⁵ on the qubit. Here we demonstrate readout of a superconducting transmon qubit through a low-backaction electro-optomechanical transducer. The modular nature of the transducer and circuit quantum electrodynamics system used in this work enable complete isolation of the qubit from optical photons, and the backaction on the qubit from the transducer is less than that imparted by thermal radiation from the environment. Moderate improvements in the transducer bandwidth and the added noise will enable us to leverage the full suite of tools available in circuit quantum electrodynamics to demonstrate transduction of non-classical signals from a superconducting qubit to the optical domain.

在环境温度下通过光学光纠缠微波频率超导量子处理器将实现安全通信和分布式量子信息处理¹的手段。然而，在这些不同的电磁频谱范围之间转换量子信号仍然是一个突出的目标^{2、3、4、5、6、7、8、9}，以及连接受限于在毫开尔文温度下运行的超导量子比特，由于光子对超导体^9,10的有害影响，电光换能器提出了相当大的挑战。此外，许多远程纠缠协议^{11、12、13、14}在量子态的上转换之前和之后都需要多个量子比特门，因此理想的换能器应该赋予最小的反作用¹⁵在量子比特上。在这里，我们演示了通过低反作用电光机械传感器读取超导传输量子比特。这项工作中使用的换能器和电路量子电动力学系统的模块化特性能够将量子比特与光子完全隔离，并且换能器对量子比特的反作用小于来自环境的热辐射所赋予的反作用。换能器带宽的适度改进和增加的噪声将使我们能够利用电路量子电动力学中可用的全套工具来演示非经典信号从超导量子位到光学域的转换。