Optical Interfaces for Superconducting Microwave Circuits*

Quantum computers will soon exceed the space and thermal cooling capacity of single cryogenic systems. One of the biggest bottlenecks is microwave lines going into and out of dilution refrigerators. Recent experiments have demonstrated optical readout of superconducting qubits [1,2] and high fidelity control and readout pulse generation [3] via an optical fiber. In order to scale these approaches to meet the size and fidelity requirements of state-of-the-art quantum processors a number of improvements are required, including microwave and optical multiplexing. We discuss active and passive heat loads and the efficiency and added noise requirements for optical to microwave and microwave to optical subsystems. We outline how these technologies could support quantum computers with sufficient qubit numbers for practical applications.

1. Delaney et al. Nature 606, 489 (2022)

2. Mirhosseini et al. Nature 588, 599 (2020)

3. Lecocq et al. Nature 591, 575 (2021)