Optical readout of superconducting qubits using nonreciprocal light propagation

Reading out quantum states is a key bottleneck for scaling superconducting-circuit quantum computers. Current schemes require many high-bandwidth coaxial cables to send and receive microwave readout pulses, leading to prohibitive thermal and physical overheads: a processor with about one hundred qubits would need several hundred readout lines. Optical readout via electro-optic transduction at the processor level is a promising alternative but currently suffers from low signal-to-noise ratios. This project aims to design an optical readout device based on a bosonic Kitaev model to enhance readout efficiency. The group of P. St-Jean has shown that this model can be encoded in the resonant modes of an electro-optic frequency comb, enabling optical readout of microwave signals with a signal-to-noise ratio that increases exponentially with the comb size. The student will use quantum optics tools to assess whether this platform can be extended to the readout of superconducting qubits and whether it offers a real performance gain. The work will involve modeling the electromagnetic field dynamics with Langevin equations, studying the electro-optic properties of commercially available devices (notably thin-film LiNbO3), and simulating the output optical signal to evaluate the platform’s feasibility.

Faculty Supervisor:

Philippe St-Jean

Student:

Partner:

École Polytechnique

Discipline:

Physics

Sector:

Education

University:

Université de Montréal

Program: