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.

Entanglement of three quantum memories via interference of three single photons


Quantum memory networks as an intermediate stage in the development of a quantum internet1 will enable a number of significant applications2,3,4,5. To connect and entangle remote quantum memories, it is best to use photons. In previous experiments6,7,8,9,10,11,12,13, entanglement of two memory nodes has been achieved via photon interference. Going beyond the state of the art by entangling many quantum nodes at a distance is highly sought after. Here, we report the entanglement of three remote quantum memories via three-photon interference. We employ laser-cooled atomic ensembles and make use of a ring cavity to enhance the overall efficiency of our memory–photon entanglement. By interfering three single photons from three separate set-ups, we create entanglement of three memories and three photons. Then, by measuring the photons and applying feed-forward, we achieve heralded entanglement between the three memories. Our experiment may be employed as a building block to construct larger and complex quantum networks14,15.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Experiment layout.
Fig. 2: Characterization of a single entangled atom–photon pair.
Fig. 3: Characterization of the sixfold entanglement |GHZ6〉.
Fig. 4: Characterization of the three-memory entanglement |GHZ3〉.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding


  1. Wehner, S., Elkouss, D. & Hanson, R. Quantum internet: a vision for the road ahead. Science 362, eaam9288 (2018).

    Article  ADS  Google Scholar 

  2. Simon, C. Towards a global quantum network. Nat. Photon. 11, 678–680 (2017).

    Article  ADS  Google Scholar 

  3. Gottesman, D., Jennewein, T. & Croke, S. Longer-baseline telescopes using quantum repeaters. Phys. Rev. Lett. 109, 070503 (2012).

    Article  ADS  Google Scholar 

  4. Kómár, P. et al. A quantum network of clocks. Nat. Phys. 10, 582–587 (2014).

    Article  Google Scholar 

  5. Pikovski, I., Zych, M., Costa, F. & Brukner, Č. Universal decoherence due to gravitational time dilation. Nat. Phys. 11, 668–672 (2015).

    Article  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

  13. Delteil, A. et al. Generation of heralded entanglement between distant hole spins. Nat. Phys. 12, 218–223 (2015).

    Article  Google Scholar 

  14. Wallnöfer, J., Zwerger, M., Muschik, C., Sangouard, N. & Dür, W. Two-dimensional quantum repeaters. Phys. Rev. A 94, 052307 (2016).

    Article  ADS  Google Scholar 

  15. Barrett, S. D., Rohde, P. P. & Stace, T. M. Scalable quantum computing with atomic ensembles. New J. Phys. 12, 093032 (2010).

    Article  ADS  Google Scholar 

  16. Sangouard, N., Simon, C., de Riedmatten, H. & Gisin, N. Quantum repeaters based on atomic ensembles and linear optics. Rev. Mod. Phys. 83, 33–80 (2011).

    Article  ADS  Google Scholar 

  17. Yang, S.-J., Wang, X.-J., Bao, X.-H. & Pan, J.-W. An efficient quantum light–matter interface with sub-second lifetime. Nat. Photon. 10, 381–384 (2016).

    Article  ADS  Google Scholar 

  18. Bao, X.-H. et al. Efficient and long-lived quantum memory with cold atoms inside a ring cavity. Nat. Phys. 8, 517–521 (2012).

    Article  Google Scholar 

  19. Yang, S.-J. et al. Highly retrievable spin-wave-photon entanglement source. Phys. Rev. Lett. 114, 210501 (2015).

    Article  ADS  Google Scholar 

  20. 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).

    Article  ADS  Google Scholar 

  21. Jiang, Y., Rui, J., Bao, X.-H. & Pan, J.-W. Dynamical zeroing of spin-wave momentum to suppress motional dephasing in an atomic-ensemble quantum memory. Phys. Rev. A 93, 063819 (2016).

    Article  ADS  Google Scholar 

  22. Saffman, M., Walker, T. G. & Molmer, K. Quantum information with Rydberg atoms. Rev. Mod. Phys. 82, 2313–2363 (2010).

    Article  ADS  Google Scholar 

  23. Li, L., Dudin, Y. O. & Kuzmich, A. Entanglement between light and an optical atomic excitation. Nature 498, 466–469 (2013).

    Article  ADS  Google Scholar 

  24. Li, J. et al. Hong-Ou-Mandel interference between two deterministic collective excitations in an atomic ensemble. Phys. Rev. Lett. 117, 180501 (2016).

    Article  ADS  Google Scholar 

  25. Gühne, O. & Tóth, G. Entanglement detection. Phys. Rep. 474, 1–75 (2009).

    Article  MathSciNet  ADS  Google Scholar 

  26. Choi, K. S., Goban, A., Papp, S. B., van Enk, S. J. & Kimble, H. J. Entanglement of spin waves among four quantum memories. Nature 468, 412–416 (2010).

    Article  ADS  Google Scholar 

  27. Pu, Y. F. et al. Experimental entanglement of 25 individually accessible atomic quantum interfaces. Sci. Adv. 4, eaar3931 (2018).

    Article  Google Scholar 

  28. Yan, Z. et al. Establishing and storing of deterministic quantum entanglement among three distant atomic ensembles. Nat. Commun. 8, 718 (2017).

    Article  ADS  Google Scholar 

  29. Maring, N. et al. Photonic quantum state transfer between a cold atomic gas and a crystal. Nature 551, 485–488 (2017).

    Article  ADS  Google Scholar 

  30. Zhao, T.-M. et al. Entangling different-color photons via time-resolved measurement and active feed forward. Phys. Rev. Lett. 112, 103602 (2014).

    Article  ADS  Google Scholar 

Download references


This work was supported by National Key R&D Program of China (no. 2017YFA0303902), Anhui Initiative in Quantum Information Technologies, National Natural Science Foundation of China, and the Chinese Academy of Sciences.

Author information

Authors and Affiliations



X.-H.B. and J.-W.P. conceived and designed the experiment. B.J. and X.-J.W. mainly carried out the experiment and collected the data with assistance from all other authors. B.J., X.-J.W. and X.-H.B. analysed the data. B.J., X.-J.W., X.-H.B. and J.-W.P. wrote the paper with input from all other authors. X.-H.B. and J.-W.P. supervised the whole project.

Corresponding authors

Correspondence to Xiao-Hui Bao or Jian-Wei Pan.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

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

Supplementary information

Supplementary Information

Supplementary notes and figures.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Jing, B., Wang, XJ., Yu, Y. et al. Entanglement of three quantum memories via interference of three single photons. Nature Photon 13, 210–213 (2019).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


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