Optically Mediated Control for Superconducting Qubits

In superconducting quantum computers, scaling the control wiring infrastructure poses significant challenges. Optical fibers present a promising alternative to traditional microwave cables, offering advantages such as lower passive heat load, reduced channel footprint, decreased crosstalk, and the potential for optical signal multiplexing.

This work explores the conversion of microwave signals to optical signals via amplitude modulation and their subsequent reconversion to microwave signals at millikelvin (mK) temperatures via a photodiode.

We systematically investigate thermal noise originating at higher temperatures affecting the qubit. The noise levels are compared to optically generated signals by analyzing qubit metrics such as temperature and the resulting unwanted qubit state transitions. We then map power dissipation at the photodiode versus parameters such as optical input power and photodiode bias voltage, and assess signal distortions from photodiode nonlinearity.

We show that controlling qubits via the optical link is possible with similar lifetimes and decoherence rates compared to the standard microwave approach. Furthermore, we quantitatively analyze the scalability of the proposed setup.