Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Telecom-heralded entanglement between multimode solid-state quantum memories


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.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Schematics of the experiment.
Fig. 2: Entanglement verification for a 2-μs AFC.
Fig. 3: Concurrence for different experimental configurations.
Fig. 4: Multimode operation of a quantum memory.

Data availability

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.


  1. 1.

    Kimble, H. J. The quantum internet. Nature 453, 1023–1030 (2008).

    ADS  CAS  Article  Google Scholar 

  2. 2.

    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).

    ADS  CAS  Article  Google Scholar 

  3. 3.

    Chou, C.-W. et al. Functional quantum nodes for entanglement distribution over scalable quantum networks. Science 316, 1316–1320 (2007).

    ADS  CAS  Article  Google Scholar 

  4. 4.

    Yuan, Z.-S. et al. Experimental demonstration of a BDCZ quantum repeater node. Nature 454, 1098–1101 (2008).

    ADS  CAS  Article  Google Scholar 

  5. 5.

    Yu, Y. et al. Entanglement of two quantum memories via fibres over dozens of kilometres. Nature 578, 240–245 (2020).

    ADS  CAS  Article  Google Scholar 

  6. 6.

    Moehring, D. L. et al. Entanglement of single-atom quantum bits at a distance. Nature 449, 68–71 (2007).

    ADS  CAS  Article  Google Scholar 

  7. 7.

    Ritter, S. et al. An elementary quantum network of single atoms in optical cavities. Nature 484, 195–200 (2012).

    ADS  CAS  Article  Google Scholar 

  8. 8.

    Hofmann, J. et al. Heralded entanglement between widely separated atoms. Science 337, 72–75 (2012).

    ADS  CAS  Article  Google Scholar 

  9. 9.

    Bernien, H. et al. Heralded entanglement between solid-state qubits separated by three metres. Nature 497, 86–90 (2013).

    ADS  CAS  Article  Google Scholar 

  10. 10.

    Usmani, I. et al. Heralded quantum entanglement between two crystals. Nat. Photon. 6, 234–237 (2012).

    ADS  CAS  Article  Google Scholar 

  11. 11.

    Stockill, R. et al. Phase-tuned entangled state generation between distant spin qubits. Phys. Rev. Lett. 119, 010503 (2017).

    ADS  CAS  Article  Google Scholar 

  12. 12.

    Sipahigil, A. et al. An integrated diamond nanophotonics platform for quantum-optical networks. Science 354, 847–850 (2016).

    ADS  CAS  Article  Google Scholar 

  13. 13.

    Hedges, M. P., Longdell, J. J., Li, Y. & Sellars, M. J. Efficient quantum memory for light. Nature 465, 1052–1056 (2010).

    ADS  CAS  Article  Google Scholar 

  14. 14.

    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).

    Google Scholar 

  15. 15.

    Seri, A. et al. Laser-written integrated platform for quantum storage of heralded single photons. Optica 5, 934–941 (2018).

    ADS  CAS  Article  Google Scholar 

  16. 16.

    Simon, C. et al. Quantum repeaters with photon pair sources and multimode memories. Phys. Rev. Lett. 98, 190503 (2007).

    ADS  Article  Google Scholar 

  17. 17.

    Chou, C.-W. et al. Measurement-induced entanglement for excitation stored in remote atomic ensembles. Nature 438, 828–832 (2005).

    ADS  CAS  Article  Google Scholar 

  18. 18.

    Humphreys, P. C. et al. Deterministic delivery of remote entanglement on a quantum network. Nature 558, 268–273 (2018).

    ADS  CAS  Article  Google Scholar 

  19. 19.

    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).

    ADS  Article  Google Scholar 

  20. 20.

    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).

    ADS  Article  Google Scholar 

  21. 21.

    Clausen, C. et al. Quantum storage of photonic entanglement in a crystal. Nature 469, 508–511 (2011).

    ADS  CAS  Article  Google Scholar 

  22. 22.

    Saglamyurek, E. et al. Broadband waveguide quantum memory for entangled photons. Nature 469, 512–515 (2011).

    ADS  CAS  Article  Google Scholar 

  23. 23.

    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).

    ADS  Article  Google Scholar 

  24. 24.

    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).

    ADS  CAS  Article  Google Scholar 

  25. 25.

    Afzelius, M., Simon, C., de Riedmatten, H. & Gisin, N. Multimode quantum memory based on atomic frequency combs. Phys. Rev. A 79, 052329 (2009).

    ADS  Article  Google Scholar 

  26. 26.

    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).

    ADS  CAS  Article  Google Scholar 

  27. 27.

    Seri, A. et al. Quantum storage of frequency-multiplexed heralded single photons. Phys. Rev. Lett. 123, 080502 (2019).

    ADS  CAS  Article  Google Scholar 

  28. 28.

    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).

    ADS  Article  Google Scholar 

  29. 29.

    Puigibert, M. G. et al. Entanglement and nonlocality between disparate solid-state quantum memories mediated by photons. Phys. Rev. Res. 2, 013039 (2020).

    CAS  Article  Google Scholar 

  30. 30.

    Caspar, P. et al. Heralded distribution of single-photon path entanglement. Phys. Rev. Lett. 125, 110506 (2020).

    ADS  CAS  Article  Google Scholar 

  31. 31.

    Liu, Y. et al. Experimental twin-field quantum key distribution through sending or not sending. Phys. Rev. Lett. 123, 100505 (2019).

    ADS  CAS  Article  Google Scholar 

  32. 32.

    Zhong, T. et al. Nanophotonic rare-earth quantum memory with optically controlled retrieval. Science 357, 1392–1395 (2017).

    ADS  MathSciNet  CAS  Article  Google Scholar 

  33. 33.

    Wootters, W. K. Entanglement of formation of an arbitrary state of two qubits. Phys. Rev. Lett. 80, 2245–2248 (1998).

    ADS  CAS  Article  Google Scholar 

Download references


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).

Author information




D.L.-R. built and operated the SPDC sources, J.V.R., A.S. and S.G. assembled and operated the solid-state quantum memory setups. D.L.-R. and S.G. designed and built the phase lock for the entanglement measurement. The experiment was conducted by D.L.-R., S.G., J.V.R. and A.S., who also jointly analysed the data. D.L.-R., S.G. and H.d.R. wrote the paper, with input from all co-authors. H.d.R. conceived the experiment and supervised the project.

Corresponding author

Correspondence to Hugues de Riedmatten.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

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.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Fig. 1 Comparison between experimental and modelled values for p11.

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.

Extended Data Table 1 Values of efficiencies for nodes A and B

Supplementary information

Supplementary Information

This file provides additional detailed information about the experiment reported in the main text.

Peer Review File

Source data

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Lago-Rivera, D., Grandi, S., Rakonjac, J.V. et al. Telecom-heralded entanglement between multimode solid-state quantum memories. Nature 594, 37–40 (2021).

Download citation


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing