Superconducting circuits can operate at higher energy efficiencies than their room-temperature counterparts and have the potential to enable large-scale control and readout of quantum computers. However, the required interface with room-temperature electronics creates difficulties in scaling up such cryogenic systems. One option is to use optical fibres as a medium in conjunction with fast optical modulators that can be efficiently driven by electrical signals at low temperatures. However, as superconducting circuits are current operated with low impedances, they interface poorly with conventional electro-optical modulators. Here we report an integrated current-driven modulator that is based on the magneto-optic effect and can operate at temperatures as low as 4 K. The device combines a magneto-optic garnet crystal with a silicon waveguide resonator and integrates an electromagnet to modulate the refractive index of the garnet. The modulator offers data rates of up to 2 Gbps with an energy consumption below 4 pJ per bit of transferred information, which could be reduced to less than 50 fJ per bit by replacing dissipative electrodes with superconductors and optimizing the geometric parameters.

超导电路可以以比室温电路更高的能量效率运行，并有可能实现量子计算机的大规模控制和读出。然而，所需的与室温电子设备的接口在扩大这种低温系统方面造成了困难。一种选择是使用光纤作为介质，结合快速光调制器，该调制器可以在低温下由电信号有效驱动。然而，由于超导电路以低阻抗电流运行，它们与传统电光调制器的接口很差。在这里，我们报告了一种基于磁光效应的集成电流驱动调制器，可以在低至 4 K 的温度下工作。该装置将磁光石榴石晶体与硅波导谐振器相结合，并集成了电磁体来调制石榴石的折射率。该调制器提供高达 2 Gbps 的数据速率，传输信息的每比特能耗低于 4 pJ，通过用超导体替换耗散电极并优化几何参数，可以将其降低到每比特 50 fJ 以下。