Future quantum networks will enable the distribution of entanglement between distant locations and allow applications in quantum communication, quantum sensing and distributed quantum computation1. At the core of this network lies the ability to generate and store entanglement at remote, interconnected quantum nodes2. Although various remote physical systems have been successfully entangled3,4,5,6,7,8,9,10,11,12, none of these realizations encompassed all of the requirements for network operation, such as compatibility with telecommunication (telecom) wavelengths and multimode operation. Here we report the demonstration of heralded entanglement between two spatially separated quantum nodes, where the entanglement is stored in multimode solid-state quantum memories. At each node a praseodymium-doped crystal13,14 stores a photon of a correlated pair15, with the second photon at telecom wavelengths. Entanglement between quantum memories placed in different laboratories is heralded by the detection of a telecom photon at a rate up to 1.4 kilohertz, and the entanglement is stored in the crystals for a pre-determined storage time up to 25 microseconds. We also show that the generated entanglement is robust against loss in the heralding path, and demonstrate temporally multiplexed operation, with 62 temporal modes. Our realization is extendable to entanglement over longer distances and provides a viable route towards field-deployed, multiplexed quantum repeaters based on solid-state resources.
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The data that support the findings of this study are available from the corresponding author upon reasonable request. Source data are provided with this paper.
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This project received funding from the European Union Horizon 2020 research and innovation programme within the Flagship on Quantum Technologies through grant 820445 (QIA) and under the Marie Skłodowska-Curie grant agreement no. 713729 (ICFOStepstone 2) and no. 758461 (proBIST), by the Gordon and Betty Moore Foundation through grant GBMF7446 to H.d.R., by the Government of Spain (PID2019-106850RB-I00, Severo Ochoa CEX2019-000910-S, BES-2017-082464), Fundació Cellex, Fundació Mir-Puig, and Generalitat de Catalunya (CERCA, AGAUR, Quantum CAT).
The authors declare no competing interests.
Peer review information Nature thanks Daniel Oblak and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.
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Extended data figures and tables
The brown dots show the scaling of p11 using the model derived from equation (7). The shaded area corresponds to the value of p11 that we measured experimentally considering one standard deviation for the error.
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Lago-Rivera, D., Grandi, S., Rakonjac, J.V. et al. Telecom-heralded entanglement between multimode solid-state quantum memories. Nature 594, 37–40 (2021). https://doi.org/10.1038/s41586-021-03481-8