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An elementary quantum network of single atoms in optical cavities

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Abstract

Quantum networks are distributed quantum many-body systems with tailored topology and controlled information exchange. They are the backbone of distributed quantum computing architectures and quantum communication. Here we present a prototype of such a quantum network based on single atoms embedded in optical cavities. We show that atom–cavity systems form universal nodes capable of sending, receiving, storing and releasing photonic quantum information. Quantum connectivity between nodes is achieved in the conceptually most fundamental way—by the coherent exchange of a single photon. We demonstrate the faithful transfer of an atomic quantum state and the creation of entanglement between two identical nodes in separate laboratories. The non-local state that is created is manipulated by local quantum bit (qubit) rotation. This efficient cavity-based approach to quantum networking is particularly promising because it offers a clear perspective for scalability, thus paving the way towards large-scale quantum networks and their applications.

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Figure 1: A cavity-based quantum network.
Figure 2: Universal quantum network node.
Figure 3: Quantum state transfer between two single-atom network nodes.
Figure 4: Remote entanglement of two single-atom nodes.
Figure 5: Controlled rotation of the entangled state.

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Acknowledgements

We thank D. Moehring for contributions during the early stage of the experiments, and B. Mayer and M. Padilla from the Walter Schottky Institut for gold coating of the fast-moving mirror. This work was supported by the Deutsche Forschungsgemeinschaft (Research Unit 635), by the European Union (Collaborative Project AQUTE) and by the Bundesministerium für Bildung und Forschung via IKT 2020 (QK_QuOReP). E.F. acknowledges support from the Alexander von Humboldt Foundation.

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All authors contributed to the experiment, the analysis of the results and the writing of the manuscript.

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Correspondence to Stephan Ritter.

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The authors declare no competing financial interests.

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Ritter, S., Nölleke, C., Hahn, C. et al. An elementary quantum network of single atoms in optical cavities. Nature 484, 195–200 (2012). https://doi.org/10.1038/nature11023

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