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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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.
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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