Quantum Network Links Atoms and Solids over Record-Breaking 49.2km Fibres

Scientists are developing quantum networks capable of distributing distinct functionalities over long distances using low-loss telecom optical fibres. Yuzhou Chai, Dahlia Ghoshal, and Nayana P. Tiwari, all from the Pritzker School of Molecular Engineering at the University of Chicago, alongside Kolar, Pingault, Bernien et al., have demonstrated a two-node hybrid network directly connecting an atomic single-photon source to a solid-state memory within the telecom C-band, crucially avoiding the need for frequency conversion or external filtering. This research is significant because both nodes achieve state-of-the-art performance at 1530nm, enabling single-photon storage and retrieval for one second across extended fibre lengths of 10.6km and 49.2km while maintaining non-classicality, and defines a high-bandwidth, natively telecom-compatible source-memory link that represents a new paradigm for designing and scaling hybrid quantum networks.

Direct spectral matching between atomic and solid-state quantum nodes at telecom wavelengths is a crucial step towards building quantum networks

Scientists have established a direct telecom network connecting atomic and solid-state quantum nodes, representing a significant step towards scalable quantum communication. This work demonstrates a high-bandwidth link operating natively in the telecom band, circumventing the need for complex frequency conversion typically required in hybrid quantum networks.
Researchers constructed a two-node hybrid network linking a single-photon source based on atomic vapour to a solid-state quantum memory, both operating at a wavelength of 1530nm. Crucially, the system achieves spectral matching without external filtering, a key innovation for simplifying network architecture and reducing signal loss.

The atomic source exhibits a heralded auto-correlation of 0.031 at a photon rate of 46 kcps, indicating high-purity single-photon emission. Simultaneously, the solid-state memory achieves a storage efficiency of 10.6% with a high multimode capacity, enabling the storage of complex quantum states. By leveraging the tunability of both nodes, the research team facilitated single-photon storage and retrieval for 1 microsecond across up to 37 temporal modes.

This capability was demonstrated over extended optical fibers spanning 10.6km in a metropolitan environment and 49.2km in a laboratory setting, while maintaining the non-classical properties of the photons. This achievement defines a new paradigm for designing and scaling hybrid quantum networks, paving the way for more versatile quantum internet architectures.

The demonstrated link supports temporally multiplexed networking between the atomic and solid-state nodes, significantly boosting entanglement rates and allowing for the integration of quantum processors. By establishing a scalable foundation for hybrid quantum networks, this work opens new frameworks for hybrid quantum information processing and long-distance quantum communication. The intrinsic tunability and native telecom-band operation of these nodes are crucial for practical quantum networking.

Demonstration of a fibre-linked hybrid quantum network with integrated single-photon source and quantum memory enables secure communication

A heralded single-photon source and a solid-state quantum memory were directly connected to establish a two-node hybrid network operating in the telecom C-band at 1530nm. The atomic single-photon source demonstrated a heralded auto-correlation function of g(2)(0) = 0.031, achieved at a photon emission rate of 46 kcps.

This performance was coupled with a quantum memory exhibiting 10.6% storage efficiency and high multimode capacity, facilitating the preservation of quantum information. The research leveraged the intrinsic tunability of both nodes to optimise spectral matching, eliminating the need for frequency conversion or external filtering.

Single-photon storage and retrieval were successfully demonstrated for 1 microsecond across 37 temporal modes. Extended optical fibers, spanning 10.6km in a metropolitan setting and 49.2km within the laboratory environment, were used to test the network’s reach and fidelity. This experimental setup involved direct connection of the nodes via optical fibers, allowing for assessment of performance over significant distances.

The atomic source and solid-state memory were meticulously aligned to achieve a 100-MHz bandwidth at the single-photon level. This precise spectral alignment enabled multiplexed interconnection and facilitated the demonstration of metropolitan-scale quantum communication. The study’s methodological innovation lies in the native telecom-band operation of both the source and memory, creating a high-bandwidth link for scalable hybrid quantum networks.

High-fidelity single-photon emission and multimode quantum memory for long-distance quantum communication are crucial advancements

Heralded auto-correlation measurements reached 0.031 at a photon rate of 46 kcps, demonstrating high-performance single-photon emission. This atomic source, operating at 1530nm, exhibits exceptional brightness and purity crucial for quantum networking applications. Simultaneously, the solid-state quantum memory achieved a storage efficiency of 10.6% with substantial multimode capacity, indicating its ability to effectively capture and retain quantum information.

The research leveraged the intrinsic tunability of both the atomic source and the solid-state memory to optimise spectral matching, enabling direct networking without the need for frequency conversion or external filtering. Single-photon storage and retrieval were successfully demonstrated for 1 microsecond across up to 37 temporal modes.

Extended fiber lengths of 10.6km, deployed in a metropolitan area, and 49.2km within a laboratory setting, facilitated the preservation of non-classicality during transmission. These results define a high-bandwidth source-memory link operating natively in the telecom band, establishing a new approach to designing and scaling hybrid quantum networks.

By jointly optimising both systems, a rate of up to 4.3 cps was achieved while maintaining non-classical correlations. The multimodality of the source-memory network was further confirmed by extending the link to 49.2km in a laboratory environment, paving the way for future advancements in long-distance quantum communication and distributed quantum computing.

Long-distance quantum storage and retrieval via a telecom-band hybrid network represents a significant step towards practical quantum communication

Scientists have demonstrated a functional two-node hybrid quantum network directly connecting an atomic single-photon source to a solid-state memory operating in the telecom C-band without frequency conversion or external filtering. Both the source and memory exhibit high performance at 1530nm, achieving a heralded auto-correlation of 0.031 at a photon rate of 46 kcps for the source and a storage efficiency of 10.6% with high multimode capacity for the memory.

This direct networking enabled single-photon storage and retrieval for one second across extended fibres of 10.6km in a metropolitan setting and 49.2km in a laboratory environment, all while preserving the non-classical properties of the photons. The established link represents a significant advancement as a building block for large-scale hybrid quantum networks, proving robust performance in a real-world, long-distance fibre deployment.

This work defines a high-bandwidth source-memory link operating natively in the telecom band, offering a new approach to designing and scaling hybrid networks for quantum communication and computation. Although the deployed fibre loop exhibited slightly higher attenuation than a standard spool, the network maintained identical correlation characteristics, indicating minimal added noise.

The authors acknowledge that the optical atomic frequency comb memory currently has a pre-determined storage time. Future research directions include utilising long-lived vanadium nuclear spins to create an on-demand retrieval system and duplicating the source-memory entanglement link to create a full quantum repeater. Furthermore, integrating this network with Rubidium atomic qubits and Erbium quantum memories could unlock new paradigms in hybrid quantum information processing, potentially reducing qubit counts and accelerating computation, ultimately offering a promising path towards scalable quantum computing networks.