A major challenge to the scalability of cryogenic computing platforms is the heat load associated with the growing number of electrical cable connections between the superconducting circuitry and the room-temperature environment. Compared with electrical cables, optical fibres have significantly lower thermal conductivity and are widely used in modern telecommunications. However, optical modulation at cryogenic temperatures remains relatively unexplored. Here we report the cryogenic electro-optical readout of a superconducting electromechanical circuit using a commercial titanium-doped lithium niobate modulator. We demonstrate coherent spectroscopy by measuring optomechanically induced transparency and incoherent thermometry by encoding the mechanical sidebands in an optical signal. We also show that our modulators can maintain their room-temperature Pockels coefficient at 800 mK. Further optimization of the modulator design—for example, by using longer waveguides and materials with a higher Pockels coefficient—could reduce the added noise of our setup to similar levels as current semiconductor microwave amplifiers.

低温计算平台的可扩展性面临的一个主要挑战是与超导电路和室温环境之间的电缆连接数量不断增加相关的热负荷。与电缆相比，光纤的热导率显着降低，在现代电信中得到广泛应用。然而，低温下的光调制仍然相对未开发。在这里，我们报告了使用商用钛掺杂铌酸锂调制器的超导机电电路的低温电光读数。我们通过在光信号中编码机械边带来测量光机械诱导的透明度和非相干测温来证明相干光谱。我们还表明，我们的调制器可以将其室温普克尔斯系数保持在 800 mK。调制器设计的进一步优化——例如，通过使用更长的波导和具有更高普克尔斯系数的材料——可以将我们设置的附加噪声降低到与当前半导体微波放大器相似的水平。