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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The data that support the findings of this study are available from the corresponding authors on request.
Gisin, N., Ribordy, G., Tittel, W. & Zbinden, H. Quantum cryptography. Rev. Mod. Phys. 74, 145–195 (2002).
Stucki, D. et al. Long-term performance of the SwissQuantum quantum key distribution network in a field environment. New J. Phys. 13, 123001 (2011).
Sasaki, M. et al. Field test of quantum key distribution in the Tokyo QKD network. Opt. Express 19, 10387–10409 (2011).
Peev, M. et al. The SECOQC quantum key distribution network in Vienna. New J. Phys. 11, 075001 (2009).
Xu, F. et al. Field experiment on a robust hierarchical metropolitan quantum cryptography network. Chin. Sci. Bull. 54, 2991–2997 (2009).
Elliott, C. et al. Current status of the DARPA quantum network. Proc SPIE 5815, 138–149 (2005).
Choi, I., Young, R. J. & Townsend, P. D. Quantum information to the home. New J. Phys. 13, 063039 (2011).
Mao, Y. et al. Integrating quantum key distribution with classical communications in backbone fiber network. Opt. Express 26, 6010–6020 (2018).
Patel, K. et al. Coexistence of high-bit-rate quantum key distribution and data on optical fiber. Phys. Rev. X 2, 041010 (2012).
Korzh, B. et al. Provably secure and practical quantum key distribution over 307 km of optical fibre. Nat. Photon. 9, 163–168 (2015).
Yin, H.-L. et al. Measurement-device-independent quantum key distribution over a 404 km optical fiber. Phys. Rev. Lett. 117, 190501 (2016).
Ursin, R. et al. Entanglement-based quantum communication over 144 km. Nat. Phys. 3, 481–486 (2007).
Liao, S.-K. et al. Satellite-to-ground quantum key distribution. Nature 549, 43–47 (2017).
Takenaka, H. et al. Satellite-to-ground quantum-limited communication using a 50-kg-class microsatellite. Nat. Photon. 11, 502–508 (2017).
Günthner, K. et al. Quantum-limited measurements of optical signals from a geostationary satellite. Optica 4, 611–616 (2017).
Törmä, P. & Gheri, K. M. Establishing multi-party entanglement with entangled photons. AIP Conf. Proc. 461, 220–228 (1999).
Townsend, P. D. Quantum cryptography on multiuser optical fibre networks. Nature 385, 47–49 (1997).
Fröhlich, B. et al. A quantum access network. Nature 501, 69–72 (2013).
Toliver, P. et al. Experimental investigation of quantum key distribution through transparent optical switch elements. IEEE Photonics Technol. Lett. 15, 1669–1671 (2003).
Chen, T.-Y. et al. Metropolitan all-pass and inter-city quantum communication network. Opt. Express 18, 27217–27225 (2010).
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).
Aktas, D. et al. Entanglement distribution over 150 km in wavelength division multiplexed channels for quantum cryptography. Laser Photonics Rev. 10, 451–457 (2016).
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).
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).
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).
Ma, X., Fung, C.-H. & Lo, H.-K. Quantum key distribution with entangled photon sources. Phys. Rev. A 76, 012307 (2007).
Ciurana, A. et al. Quantum metropolitan optical network based on wavelength division multiplexing. Opt. Express 22, 1576–1593 (2014).
He, G. P. Simple quantum protocols for the millionaire problem with a semi-honest third party. Int. J. Quant. Inf. 11, 1350025 (2013).
Islam, T. & Wehner, S. Asynchronous reference frame agreement in a quantum network. New J. Phys. 18, 033018 (2016).
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).
Oh, J., Antonelli, C. & Brodsky, M. Coincidence rates for photon pairs in WDM environment. J. Lightwave Technol. 29, 324–329 (2011).
Ghalbouni, J., Agha, I., Frey, R., Diamanti, E. & Zaquine, I. Experimental wavelength-division-multiplexed photon-pair distribution. Opt. Lett. 38, 34–36 (2013).
Monteiro, F., Martin, A., Sanguinetti, B., Zbinden, H. & Thew, R. T. Narrowband photon pair source for quantum networks. Opt. Express 22, 4371–4378 (2014).
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).
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).
Inagaki, T. et al. Entanglement distribution over 300 km of fiber. Opt. Express 21, 23241–23249 (2013).
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).
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.
Nature thanks V. Martin and the other anonymous reviewer(s) for their contribution to the peer review of this work.
The authors declare no competing interests.
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 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.
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Wengerowsky, S., Joshi, S.K., Steinlechner, F. et al. An entanglement-based wavelength-multiplexed quantum communication network. Nature 564, 225–228 (2018). https://doi.org/10.1038/s41586-018-0766-y
- Quantum Communication Network
- Polarization Analysis Module
- Wavelength Channels
- Active Optical Switching
- Idler Photons
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