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An entanglement-based wavelength-multiplexed quantum communication network


Quantum key distribution1 has reached the level of maturity required for deployment in real-world scenarios2,3,4,5,6. It has previously been shown to operate alongside classical communication in the same telecommunication fibre7,8,9 and over long distances in fibre10,11 and in free-space links12,13,14,15. Despite these advances, the practical applicability of quantum key distribution is curtailed by the fact that most implementations and protocols are limited to two communicating parties. Quantum networks scale the advantages of quantum key distribution protocols to more than two distant users. Here we present a fully connected quantum network architecture in which a single entangled photon source distributes quantum states to many users while minimizing the resources required for each. Further, it does so without sacrificing security or functionality relative to two-party communication schemes. We demonstrate the feasibility of our approach using a single source of bipartite polarization entanglement, which is multiplexed into 12 wavelength channels. Six states are then distributed between four users in a fully connected graph using only one fibre and one polarization analysis module per user. Because no adaptations of the entanglement source are required to add users, the network can readily be scaled to a large number of users, without requiring trust in the provider of the source. Unlike previous attempts at multi-user networks, which have been based on active optical switches and therefore limited to some duty cycle, our implementation is fully passive and thus has the potential for unprecedented quantum communication speeds.

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Fig. 1: Network architecture and experimental set-up.
Fig. 2: Spectrum and wavelength multiplexing.
Fig. 3: Experimental results.

Data availability

The data that support the findings of this study are available from the corresponding authors on request.


  1. 1.

    Gisin, N., Ribordy, G., Tittel, W. & Zbinden, H. Quantum cryptography. Rev. Mod. Phys. 74, 145–195 (2002).

    ADS  Article  MATH  Google Scholar 

  2. 2.

    Stucki, D. et al. Long-term performance of the SwissQuantum quantum key distribution network in a field environment. New J. Phys. 13, 123001 (2011).

    ADS  Article  Google Scholar 

  3. 3.

    Sasaki, M. et al. Field test of quantum key distribution in the Tokyo QKD network. Opt. Express 19, 10387–10409 (2011).

    ADS  CAS  Article  Google Scholar 

  4. 4.

    Peev, M. et al. The SECOQC quantum key distribution network in Vienna. New J. Phys. 11, 075001 (2009).

    ADS  Article  CAS  Google Scholar 

  5. 5.

    Xu, F. et al. Field experiment on a robust hierarchical metropolitan quantum cryptography network. Chin. Sci. Bull. 54, 2991–2997 (2009).

    Article  Google Scholar 

  6. 6.

    Elliott, C. et al. Current status of the DARPA quantum network. Proc SPIE 5815, 138–149 (2005).

    ADS  Article  Google Scholar 

  7. 7.

    Choi, I., Young, R. J. & Townsend, P. D. Quantum information to the home. New J. Phys. 13, 063039 (2011).

    ADS  Article  Google Scholar 

  8. 8.

    Mao, Y. et al. Integrating quantum key distribution with classical communications in backbone fiber network. Opt. Express 26, 6010–6020 (2018).

    ADS  CAS  Article  Google Scholar 

  9. 9.

    Patel, K. et al. Coexistence of high-bit-rate quantum key distribution and data on optical fiber. Phys. Rev. X 2, 041010 (2012).

    Google Scholar 

  10. 10.

    Korzh, B. et al. Provably secure and practical quantum key distribution over 307 km of optical fibre. Nat. Photon. 9, 163–168 (2015).

    ADS  CAS  Article  Google Scholar 

  11. 11.

    Yin, H.-L. et al. Measurement-device-independent quantum key distribution over a 404 km optical fiber. Phys. Rev. Lett. 117, 190501 (2016).

    ADS  Article  Google Scholar 

  12. 12.

    Ursin, R. et al. Entanglement-based quantum communication over 144 km. Nat. Phys. 3, 481–486 (2007).

    CAS  Article  Google Scholar 

  13. 13.

    Liao, S.-K. et al. Satellite-to-ground quantum key distribution. Nature 549, 43–47 (2017).

    ADS  CAS  Article  Google Scholar 

  14. 14.

    Takenaka, H. et al. Satellite-to-ground quantum-limited communication using a 50-kg-class microsatellite. Nat. Photon. 11, 502–508 (2017).

    CAS  Article  Google Scholar 

  15. 15.

    Günthner, K. et al. Quantum-limited measurements of optical signals from a geostationary satellite. Optica 4, 611–616 (2017).

    Article  Google Scholar 

  16. 16.

    Törmä, P. & Gheri, K. M. Establishing multi-party entanglement with entangled photons. AIP Conf. Proc. 461, 220–228 (1999).

    ADS  Google Scholar 

  17. 17.

    Townsend, P. D. Quantum cryptography on multiuser optical fibre networks. Nature 385, 47–49 (1997).

    ADS  CAS  Article  Google Scholar 

  18. 18.

    Fröhlich, B. et al. A quantum access network. Nature 501, 69–72 (2013).

    ADS  Article  CAS  Google Scholar 

  19. 19.

    Toliver, P. et al. Experimental investigation of quantum key distribution through transparent optical switch elements. IEEE Photonics Technol. Lett. 15, 1669–1671 (2003).

    ADS  Article  Google Scholar 

  20. 20.

    Chen, T.-Y. et al. Metropolitan all-pass and inter-city quantum communication network. Opt. Express 18, 27217–27225 (2010).

    ADS  Article  Google Scholar 

  21. 21.

    Chang, X.-Y., Deng, D.-L., Yuan, X.-X. et al. Experimental realization of an entanglement access network and secure multi-party computation. Sci. Rep. 6, 29453 (2016).

    ADS  Article  PubMed  PubMed Central  Google Scholar 

  22. 22.

    Aktas, D. et al. Entanglement distribution over 150 km in wavelength division multiplexed channels for quantum cryptography. Laser Photonics Rev. 10, 451–457 (2016).

    ADS  Article  Google Scholar 

  23. 23.

    Zhu, E. Y. et al. Multi-party agile QKD network with a fiber-based entangled source. In 2015 Conf. on Lasers and Electro-optics (CLEO): Science and Innovations abstr. JW2A.10 (Optical Society of America, 2015).

  24. 24.

    Lim, H. C., Yoshizawa, A., Tsuchida, H. & Kikuchi, K. Broadband source of telecom-band polarization-entangled photon-pairs for wavelength-multiplexed entanglement distribution. Opt. Express 16, 16052–16057 (2008).

    ADS  CAS  Article  Google Scholar 

  25. 25.

    Herbauts, I., Blauensteiner, B., Poppe, A., Jennewein, T. & Hübel, H. Demonstration of active routing of entanglement in a multi-user network. Opt. Express 21, 29013–29024 (2013).

    ADS  CAS  Article  Google Scholar 

  26. 26.

    Ma, X., Fung, C.-H. & Lo, H.-K. Quantum key distribution with entangled photon sources. Phys. Rev. A 76, 012307 (2007).

    ADS  Article  CAS  Google Scholar 

  27. 27.

    Ciurana, A. et al. Quantum metropolitan optical network based on wavelength division multiplexing. Opt. Express 22, 1576–1593 (2014).

    ADS  CAS  Article  Google Scholar 

  28. 28.

    He, G. P. Simple quantum protocols for the millionaire problem with a semi-honest third party. Int. J. Quant. Inf. 11, 1350025 (2013).

    MathSciNet  Article  MATH  Google Scholar 

  29. 29.

    Islam, T. & Wehner, S. Asynchronous reference frame agreement in a quantum network. New J. Phys. 18, 033018 (2016).

    ADS  MathSciNet  Article  CAS  Google Scholar 

  30. 30.

    Gayer, O., Sacks, Z., Galun, E. & Arie, A. Temperature and wavelength dependent refractive index equations for MgO-doped congruent and stoichiometric LiNbO3. Appl. Phys. B 91, 343–348 (2008).

    ADS  CAS  Article  Google Scholar 

  31. 31.

    Oh, J., Antonelli, C. & Brodsky, M. Coincidence rates for photon pairs in WDM environment. J. Lightwave Technol. 29, 324–329 (2011).

    ADS  Article  Google Scholar 

  32. 32.

    Ghalbouni, J., Agha, I., Frey, R., Diamanti, E. & Zaquine, I. Experimental wavelength-division-multiplexed photon-pair distribution. Opt. Lett. 38, 34–36 (2013).

    ADS  Article  Google Scholar 

  33. 33.

    Monteiro, F., Martin, A., Sanguinetti, B., Zbinden, H. & Thew, R. T. Narrowband photon pair source for quantum networks. Opt. Express 22, 4371–4378 (2014).

    ADS  CAS  Article  Google Scholar 

  34. 34.

    Kim, T., Fiorentino, M. & Wong, F. N. C. Phase-stable source of polarization-entangled photons using a polarization Sagnac interferometer. Phys. Rev. A 73, 012316 (2006).

    ADS  Article  CAS  Google Scholar 

  35. 35.

    Fedrizzi, A., Herbst, T., Poppe, A., Jennewein, T. & Zeilinger, A. A wavelength-tunable fiber-coupled source of narrowband entangled photons. Opt. Express 15, 15377–15386 (2007).

    ADS  CAS  Article  Google Scholar 

  36. 36.

    Inagaki, T. et al. Entanglement distribution over 300 km of fiber. Opt. Express 21, 23241–23249 (2013).

    ADS  Article  Google Scholar 

  37. 37.

    Roslund, J., De Araújo, R. M., Jiang, S., Fabre, C. & Treps, N. Wavelength-multiplexed quantum networks with ultrafast frequency combs. Nat. Photon. 8, 109–112 (2014).

    ADS  CAS  Article  Google Scholar 

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We thank J. Slim for help with the software and E. Acuña Ortega for assistance in the laboratory. We acknowledge financial support from the Austrian Research Promotion Agency (FFG) Projects—Agentur für Luft- und Raumfahrt (FFG-ALR contracts 854022 and 866025), the European Union (EU) under Horizon 2020 contract number FETOPEN-801060 quantum-enhanced on-chip interference microscopy (Q-MIC) and the Austrian Academy of Sciences.

Reviewer information

Nature thanks V. Martin and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author information




The set-up was built by S.W. and the experiment was conducted by S.W. and S.K.J. The network architecture was conceived by S.K.J. and S.W. The source was designed by F.S., S.W. and S.K.J. H.H. helped with the detection of the single photons. R.U. contributed to the experimental design, source and network and to supervising the project. The paper was written by S.W., S.K.J. and F.S. All authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to Sören Wengerowsky or Rupert Ursin.

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The authors declare no competing interests.

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Extended data figures and tables

Extended Data Fig. 1 Calculated fidelities and quantum-bit error rate (QBER) for two to nine users versus the system efficiency and equivalent fibre length, assuming an attenuation of 0.2 dB km−1.

a, Using detectors with a 1 ns timing jitter. This is great for cheap networks with low losses (those over a small area such as a LAN). b, Using detectors with a 100 ps jitter allows us to sustain much higher losses and many more users. This is useful for long-distance inter-city links. Both graphs were calculated using a generated pair rate of 1.7 million pairs per second and a dark count rate of 500 per second per detector.

Extended Data Table 1 Measured fidelities
Extended Data Table 2 Count rates

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Cite this article

Wengerowsky, S., Joshi, S.K., Steinlechner, F. et al. An entanglement-based wavelength-multiplexed quantum communication network. Nature 564, 225–228 (2018).

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  • Quantum Communication Network
  • Polarization Analysis Module
  • Wavelength Channels
  • Active Optical Switching
  • Idler Photons

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