Skip to main content

Thank you for visiting nature.com. 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.

  • Letter
  • Published:

Experimental demonstration of non-bilocality with truly independent sources and strict locality constraints

Abstract

The ongoing interest in creating a secure global quantum network culminated recently in the demonstration of transcontinental quantum communication1. There is a pressing need to examine the properties attached to a quantum network architecture from multiple perspectives, including physics foundations2, communication security3, the efficient use of resources and innovative technological applications4,5. Here, we present an experimental realization of a five-node quantum network, in which quantum sources at two nodes deliver entangled photon pairs to three measurement nodes. With relevant events between five nodes separated space-like, we demonstrate violation of the Bell inequality and bilocal inequality6, with the locality, measurement independence and quantum source independence loopholes closed simultaneously in a quantum network. This experimental realization may be valuable for the design and implementation of future quantum networks.

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

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Space–time diagram of the simplest quantum network.
Fig. 2: Schematics for testing the bilocality in a network.
Fig. 3: Space–time configuration of relevant events in each experimental trial.
Fig. 4: \({\cal{B}}_{13}\) and \(\cal{S}\) versus noise parameter p.

Similar content being viewed by others

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

References

  1. Liao, S.-K. et al. Satellite-relayed intercontinental quantum network. Phys. Rev. Lett. 120, 030501 (2018).

    Article  ADS  Google Scholar 

  2. Brunner, N., Cavalcanti, D., Pironio, S., Scarani, V. & Wehner, S. Bell nonlocality. Rev. Mod. Phys. 86, 419–478 (2014).

    Article  ADS  Google Scholar 

  3. Vazirani, U. & Vidick, T. Fully device-independent quantum key distribution. Phys. Rev. Lett. 113, 140501 (2014).

    Article  ADS  Google Scholar 

  4. Colbeck, R. A. Quantum and Relativistic Protocols for Secure Multi-party Computation. PhD thesis, Univ. Cambridge (2007).

  5. Lee, C. M. & Hoban, M. J. Towards device-independent information processing on general quantum networks. Phys. Rev. Lett. 120, 020504 (2018).

    Article  ADS  MathSciNet  Google Scholar 

  6. Branciard, C., Gisin, N. & Pironio, S. Characterizing the nonlocal correlations created via entanglement swapping. Phys. Rev. Lett. 104, 170401 (2010).

    Article  ADS  Google Scholar 

  7. Einstein, A., Podolsky, B. & Rosen, N. Can quantum-mechanical description of physical reality be considered complete? Phys. Rev. 47, 777–780 (1935).

    Article  ADS  Google Scholar 

  8. Bell, J. S. On the Einstein–Podolsky–Rosen paradox. Physics 1, 195–200 (1964).

    Article  MathSciNet  Google Scholar 

  9. Hensen, B. et al. Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres. Nature 526, 682–686 (2015).

    Article  ADS  Google Scholar 

  10. Giustina, M. et al. Significant-loophole-free test of Bell’s theorem with entangled photons. Phys. Rev. Lett. 115, 250401 (2015).

    Article  ADS  Google Scholar 

  11. Shalm, L. K. et al. Strong loophole-free test of local realism. Phys. Rev. Lett. 115, 250402 (2015).

    Article  ADS  Google Scholar 

  12. Rosenfeld, W. et al. Event-ready Bell test using entangled atoms simultaneously closing detection and locality loopholes. Phys. Rev. Lett. 119, 010402 (2017).

    Article  ADS  Google Scholar 

  13. Chaves, R., Kueng, R., Brask, J. B. & Gross, D. Unifying framework for relaxations of the causal assumptions in Bell’s theorem. Phys. Rev. Lett. 114, 140403 (2015).

    Article  ADS  Google Scholar 

  14. Chaves, R. Polynomial Bell inequalities. Phys. Rev. Lett. 116, 010402 (2016).

    Article  ADS  MathSciNet  Google Scholar 

  15. Rosset, D. et al. Nonlinear Bell inequalities tailored for quantum networks. Phys. Rev. Lett. 116, 010403 (2016).

    Article  ADS  MathSciNet  Google Scholar 

  16. Fritz, T. Beyond Bell’s theorem II: scenarios with arbitrary causal structure. Commun. Math. Phys. 341, 391–434 (2016).

    Article  ADS  MathSciNet  Google Scholar 

  17. Żukowski, M., Zeilinger, A., Horne, M. & Ekert, A. ‘Event-ready-detectors’ Bell experiment via entanglement swapping. Phys. Rev. Lett. 71, 4287–4290 (1993).

    Article  ADS  Google Scholar 

  18. Aspect, A., Grangier, P. & Roger, G. Experimental tests of realistic local theories via Bell’s theorem. Phys. Rev. Lett. 47, 460–463 (1981).

    Article  ADS  Google Scholar 

  19. Carvacho, G. et al. Experimental violation of local causality in a quantum network. Nat. Commun. 8, 14775 (2017).

    Article  ADS  Google Scholar 

  20. Saunders, D. J., Bennet, A. J., Branciard, C. & Pryde, G. J. Experimental demonstration of nonbilocal quantum correlations. Sci. Adv. 3, e1602743 (2017).

    Article  ADS  Google Scholar 

  21. Andreoli, F. et al. Experimental bilocality violation without shared reference frames. Phys. Rev. A 95, 062315 (2017).

    Article  ADS  Google Scholar 

  22. Weinfurter, H. Experimental Bell-state analysis. Europhys. Lett. 25, 559–564 (1994).

    Article  ADS  Google Scholar 

  23. Clauser, J. F., Horne, M. A., Shimony, A. & Holt, R. A. Proposed experiment to test local hidden-variable theories. Phys. Rev. Lett. 23, 880–884 (1969).

    Article  ADS  Google Scholar 

  24. Sun, Q.-C. et al. Quantum teleportation with independent sources and prior entanglement distribution over a network. Nat. Photon. 10, 671–675 (2016).

    Article  ADS  Google Scholar 

  25. Abellán, C., Amaya, W., Mitrani, D., Pruneri, V. & Mitchell, M. W. Generation of fresh and pure random numbers for loophole-free Bell tests. Phys. Rev. Lett. 115, 250403 (2015).

    Article  ADS  Google Scholar 

  26. Hong, C., Ou, Z. & Mandel, L. Measurement of subpicosecond time intervals between two photons by interference. Phys. Rev. Lett. 59, 2044–2046 (1987).

    Article  ADS  Google Scholar 

  27. Handsteiner, J. et al. Cosmic Bell test: measurement settings from Milky Way stars. Phys. Rev. Lett. 118, 060401 (2017).

    Article  ADS  Google Scholar 

  28. Li, M.-H. et al. Test of local realism into the past without detection and locality loopholes. Phys. Rev. Lett. 121, 080404 (2018).

    Article  ADS  Google Scholar 

  29. Tavakoli, A., Skrzypczyk, P., Cavalcanti, D. & Acín, A. Nonlocal correlations in the star-network configuration. Phys. Rev. A 90, 062109 (2014).

    Article  ADS  Google Scholar 

  30. Andreoli, F., Carvacho, G., Santodonato, L., Chaves, R. & Sciarrino, F. Maximal qubit violation of n-locality inequalities in a star-shaped quantum network. New J. Phys. 19, 113020 (2017).

    Article  ADS  Google Scholar 

  31. Gisin, N. The elegant joint quantum measurement and some conjectures about n-locality in the triangle and other configurations. Preprint at http://arxiv.org/abs/1708.05556 (2017).

  32. Branciard, C., Rosset, D., Gisin, N. & Pironio, S. Bilocal versus nonbilocal correlations in entanglement-swapping experiments. Phys. Rev. A 85, 032119 (2012).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

We thank Y. Liu, Y. Li and Y.-Q. Nie for enlightening discussions, Y.-L. Mao for assistance, K.-X. Yang for help with the aerial photographs and Quantum Ctek for providing the components used in the QRNGs. This work was supported by the National Key R&D Program of China (2017YFA0303900, 2017YFA0304000), the National Natural Science Foundation of China and the Chinese Academy of Sciences.

Author information

Authors and Affiliations

Authors

Contributions

Q.-C.S., Q.Z., J.F. and J.-W.P. conceived and designed the experiments. B.B. and J.Z. built the QRNGs. W.Z., H.L., L.Y. and Z.W. fabricated the SNSPDs. Q.-C.S. and Y.-F.J. built the experimental network and carried out the experiment. X.J. and X.C. provided experimental assistance. Q.-C.S. and Y.-F.J. analysed the data. Q.-C.S., Q.Z., J.F. and J.-W.P. wrote the manuscript, with input from all authors.

Corresponding authors

Correspondence to Qiang Zhang, Jingyun Fan 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

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Sun, QC., Jiang, YF., Bai, B. et al. Experimental demonstration of non-bilocality with truly independent sources and strict locality constraints. Nat. Photonics 13, 687–691 (2019). https://doi.org/10.1038/s41566-019-0502-7

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41566-019-0502-7

This article is cited by

Search

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