Letter | Published:

An entanglement-based wavelength-multiplexed quantum communication network

Naturevolume 564pages225228 (2018) | Download Citation

Abstract

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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Data availability

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

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Acknowledgements

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

Author notes

    • Siddarth Koduru Joshi

    Present address: Quantum Engineering Technology Labs, H. H. Wills Physics Laboratory, Department of Electrical and Electronic Engineering, University of Bristol, Bristol, UK

    • Fabian Steinlechner

    Present address: Fraunhofer Institute for Applied Optics and Precision Engineering, Jena, Germany

    • Fabian Steinlechner

    Present address: Friedrich Schiller Universitz Jena, Abbe Center for Photonics, Jena, Germany

Affiliations

  1. Institute for Quantum Optics and Quantum Information—Vienna, Austrian Academy of Sciences, Vienna, Austria

    • Sören Wengerowsky
    • , Siddarth Koduru Joshi
    • , Fabian Steinlechner
    •  & Rupert Ursin
  2. Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Vienna, Austria

    • Sören Wengerowsky
    • , Siddarth Koduru Joshi
    • , Fabian Steinlechner
    •  & Rupert Ursin
  3. Austrian Institute of Technology, Vienna, Austria

    • Hannes Hübel
  4. Fraunhofer Institute for Applied Optics and Precision Engineering, Jena, Germany

    • Fabian Steinlechner
  5. Friedrich Schiller Universitz Jena, Abbe Center for Photonics, Jena, Germany

    • Fabian Steinlechner

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Contributions

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.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Sören Wengerowsky or Rupert Ursin.

Extended data figures and tables

  1. 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.

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

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DOI

https://doi.org/10.1038/s41586-018-0766-y

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