All-optical control and multiplexed readout of multiple superconducting qubits

TL;DR

This paper presents an all-optical I/O architecture for superconducting qubits, enabling multiplexed control and readout without degrading qubit coherence, thus addressing scalability challenges in quantum computing.

Contribution

It introduces a broadband traveling-wave Brillouin transducer for optical readout and fiber-integrated photodiodes for control, demonstrating scalable optical interconnects for superconducting quantum circuits.

Findings

Achieved simultaneous optical readout of two qubits with frequency multiplexing.

Maintained qubit coherence times with no measurable degradation.

Single-qubit gate fidelity reduced by only 0.19% using optical control.

Abstract

Superconducting quantum circuits operate at millikelvin temperatures, typically requiring independent microwave cables for each qubit for connecting room-temperature control and readout electronics. However, scaling to large-scale processors hosting hundreds of qubits faces a severe input/output (I/O) bottleneck, as the dense cable arrays impose prohibitive constraints on physical footprint, thermal load, wiring complexity, and cost. Here we demonstrate a complete optical I/O architecture for superconducting quantum circuits, in which all control and readout signals are transmitted exclusively via optical photons. Employing a broadband traveling-wave Brillouin microwave-to-optical transducer, we achieve simultaneous frequency-multiplexed optical readout of two qubits. Combined with fiber-integrated photodiode arrays for control signal delivery, this closed-loop optical I/O introduces no measurable degradation to qubit coherence times, with an optically driven single-qubit gate fidelity showing only a 0.19% reduction relative to standard microwave operation. These results establish optical interconnects as a viable path toward large-scale superconducting quantum processors, and open the possibility of networking multiple superconducting quantum computers housed in separate dilution refrigerators through a centralized room-temperature control infrastructure.