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.
Kimble, H. J. The quantum internet. Nature 453, 1023–1030 (2008).
Duan, L.-M., Lukin, M. D., Cirac, J. I. & Zoller, P. Long-distance quantum communication with atomic ensembles and linear optics. Nature 414, 413–418 (2001).
Chou, C.-W. et al. Functional quantum nodes for entanglement distribution over scalable quantum networks. Science 316, 1316–1320 (2007).
Yuan, Z.-S. et al. Experimental demonstration of a BDCZ quantum repeater node. Nature 454, 1098–1101 (2008).
Yu, Y. et al. Entanglement of two quantum memories via fibres over dozens of kilometres. Nature 578, 240–245 (2020).
Moehring, D. L. et al. Entanglement of single-atom quantum bits at a distance. Nature 449, 68–71 (2007).
Ritter, S. et al. An elementary quantum network of single atoms in optical cavities. Nature 484, 195–200 (2012).
Hofmann, J. et al. Heralded entanglement between widely separated atoms. Science 337, 72–75 (2012).
Bernien, H. et al. Heralded entanglement between solid-state qubits separated by three metres. Nature 497, 86–90 (2013).
Usmani, I. et al. Heralded quantum entanglement between two crystals. Nat. Photon. 6, 234–237 (2012).
Stockill, R. et al. Phase-tuned entangled state generation between distant spin qubits. Phys. Rev. Lett. 119, 010503 (2017).
Sipahigil, A. et al. An integrated diamond nanophotonics platform for quantum-optical networks. Science 354, 847–850 (2016).
Hedges, M. P., Longdell, J. J., Li, Y. & Sellars, M. J. Efficient quantum memory for light. Nature 465, 1052–1056 (2010).
Seri, A. et al. Quantum correlations between single telecom photons and a multimode on-demand solid-state quantum memory. Phys. Rev. X 7, 021028 (2017).
Seri, A. et al. Laser-written integrated platform for quantum storage of heralded single photons. Optica 5, 934–941 (2018).
Simon, C. et al. Quantum repeaters with photon pair sources and multimode memories. Phys. Rev. Lett. 98, 190503 (2007).
Chou, C.-W. et al. Measurement-induced entanglement for excitation stored in remote atomic ensembles. Nature 438, 828–832 (2005).
Humphreys, P. C. et al. Deterministic delivery of remote entanglement on a quantum network. Nature 558, 268–273 (2018).
de Riedmatten, H., Afzelius, M., Staudt, M. U., Simon, C. & Gisin, N. A solid-state light–matter interface at the single-photon level. Nature 456, 773–777 (2008).
Laplane, C., Jobez, P., Etesse, J., Gisin, N. & Afzelius, M. Multimode and long-lived quantum correlations between photons and spins in a crystal. Phys. Rev. Lett. 118, 210501 (2017).
Clausen, C. et al. Quantum storage of photonic entanglement in a crystal. Nature 469, 508–511 (2011).
Saglamyurek, E. et al. Broadband waveguide quantum memory for entangled photons. Nature 469, 512–515 (2011).
Ferguson, K. R., Beavan, S. E., Longdell, J. J. & Sellars, M. J. Generation of light with multimode time-delayed entanglement using storage in a solid-state spin-wave quantum memory. Phys. Rev. Lett. 117, 020501 (2016).
Kutluer, K. et al. Time entanglement between a photon and a spin wave in a multimode solid-state quantum memory. Phys. Rev. Lett. 123, 030501 (2019).
Afzelius, M., Simon, C., de Riedmatten, H. & Gisin, N. Multimode quantum memory based on atomic frequency combs. Phys. Rev. A 79, 052329 (2009).
Sinclair, N. et al. Spectral multiplexing for scalable quantum photonics using an atomic frequency comb quantum memory and feed-forward control. Phys. Rev. Lett. 113, 053603 (2014).
Seri, A. et al. Quantum storage of frequency-multiplexed heralded single photons. Phys. Rev. Lett. 123, 080502 (2019).
Yang, T. S. et al. Multiplexed storage and real-time manipulation based on a multiple degree-of-freedom quantum memory. Nat. Commun. 9, 3407 (2018).
Puigibert, M. G. et al. Entanglement and nonlocality between disparate solid-state quantum memories mediated by photons. Phys. Rev. Res. 2, 013039 (2020).
Caspar, P. et al. Heralded distribution of single-photon path entanglement. Phys. Rev. Lett. 125, 110506 (2020).
Liu, Y. et al. Experimental twin-field quantum key distribution through sending or not sending. Phys. Rev. Lett. 123, 100505 (2019).
Zhong, T. et al. Nanophotonic rare-earth quantum memory with optically controlled retrieval. Science 357, 1392–1395 (2017).
Wootters, W. K. Entanglement of formation of an arbitrary state of two qubits. Phys. Rev. Lett. 80, 2245–2248 (1998).
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