Coherent control of a superconducting qubit using light

Abstract

Quantum communications technologies require a network of quantum processors connected with low-loss and low-noise communication channels capable of distributing entangled states. Superconducting microwave qubits operating in cryogenic environments have emerged as promising candidates for quantum processor nodes. However, scaling these systems is challenging because they require bulky microwave components with high thermal loads that can quickly overwhelm the cooling power of a dilution refrigerator. Telecommunication frequency optical signals, however, can be fabricated in significantly smaller form factors to avoid challenges caused by high signal loss, noise sensitivity and thermal loads due to their high carrier frequency and propagation in silica optical fibres. Transduction of information by means of coherent links between optical and microwave frequencies is therefore critical to leverage the advantages of optics for superconducting microwave qubits, while also enabling superconducting processors to be linked with low-loss optical interconnects. Here, we demonstrate coherent optical control of a superconducting qubit. We achieve this by developing a microwave–optical quantum transducer that operates with up to 1.18% conversion efficiency with low added microwave noise, and we demonstrate optically driven Rabi oscillations in a superconducting qubit.