A kilometer photonic link connecting superconducting circuits in two dilution refrigerators

TL;DR

This paper demonstrates a coherent photonic link connecting superconducting circuits in separate refrigerators over 1 km, advancing scalable quantum networks with improved transduction efficiency.

Contribution

It presents the first experimental realization of a coherent microwave-to-optical link between superconducting circuits in different dilution refrigerators using electro-optic transducers.

Findings

Achieved signal transfer between two superconducting circuits in separate refrigerators.

Connected transducers via 1-km optical fiber enabling long-distance quantum communication.

Enhanced transduction efficiency by over 80 dB compared to commercial modulators.

Abstract

Superconducting quantum processors are a leading platform for implementing practical quantum computation algorithms. Although superconducting quantum processors with hundreds of qubits have been demonstrated, their further scaling up is constrained by the physical size and cooling power of dilution refrigerators. This constraint can be overcome by constructing a quantum network to interconnect qubits hosted in different refrigerators, which requires microwave-to-optical transducers to enable low-loss signal transmission over long distances. Despite that various designs and demonstrations have achieved high-efficiency and low-added-noise transducers, a coherent photonic link between separate refrigerators has not yet been realized. In this work, we experimentally demonstrate coherent signal transfer between two superconducting circuits housed in separate dilution refrigerators, enabled by a pair of frequency-matched aluminum nitride electro-optic transducers connected via a 1-km telecom optical fiber. With transducers at each node achieving >0.1% efficiency, an overall 80 dB improvement in transduction efficiency over commercial electro-optic modulators is attainable, paving the way towards a fully quantum-enabled link. This work provides critical design guidelines towards scalable superconducting quantum networks interconnected by photonic links.