Cryogenic microwave link for quantum local area networks

TL;DR

This paper demonstrates a cryogenic microwave link connecting two superconducting quantum processors over 6.6 meters, successfully distributing entanglement and maintaining quantum coherence at elevated temperatures, advancing distributed quantum computing.

Contribution

It introduces a prototype cryogenic microwave link for quantum local area networks, enabling entanglement distribution over long distances between superconducting circuits.

Findings

Achieved 2.10 dB squeezing and negativity of 0.501 in entanglement.

Distributed entanglement is preserved up to 1 K channel temperature.

Demonstrated feasibility of microwave quantum communication at elevated temperatures.

Abstract

Scalable quantum information processing with superconducting circuits is expected to advance from individual processors located in single dilution refrigerators to more powerful distributed quantum computing systems. The realization of hardware platforms for quantum local area networks (QLANs) compatible with superconducting technology is of high importance in order to achieve a practical quantum advantage. Here, we present a fundamental prototype platform for a microwave QLAN based on a cryogenic link connecting two separate dilution cryostats over a distance of $6.6$ m with a base temperature of $52$ mK in the center. Superconducting microwave coaxial cables are employed to form a quantum communication channel between the distributed network nodes. We demonstrate the continuous-variable entanglement distribution between the remote dilution refrigerators in the form of two-mode squeezed microwave states, reaching squeezing of $2.10 \pm 0.02$ dB and negativity of $0.501 \pm 0.011$. Furthermore, we show that quantum entanglement is preserved at channel center temperatures up to $1$ K, paving the way towards microwave quantum communication at elevated temperatures. Consequently, such a QLAN system can form the backbone for future distributed quantum computing with superconducting circuits.