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Reply to 'Discrete and continuous variables for measurement-device-independent quantum cryptography'

Nature Photonics volume 9, pages 773–775 (2015)Cite this article

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Pirandola et al. reply

In a recent correspondence, Xu et al.1 claimed that discrete variable (DV) measurement-device-independent (MDI) quantum key distribution (QKD) (refs. 2,3) would compete with its continuous-variable (CV) counterpart4 at metropolitan distances. Here we discuss how their analysis supports the opposite, showing that our experimental CV rate4 (achieved with practical room-temperature devices) remains one order of magnitude higher than their purely numerical extrapolation for qubits based on nearly ideal parameters and cryogenic detectors — conditions that we consider unsuitable for a realistic and scalable high-rate network that is expected to run on cheap room-temperature devices, including mobile devices. As we show here, our experimental CV rate is confirmed to be two to three orders of magnitude higher than the rate of any realistic simulation of practical DV MDI QKD over short to medium distances. Before clarifying this, we rectify several incorrect claims made against CV MDI QKD and, more generally, CV QKD.

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Figure 1: Comparison between the rates (bits per relay use) of CV MDI QKD and DV MDI QKD versus total Alice–Bob distance (in fibre-equivalent at 0.2 dB per km) for different configurations of the relay.

References

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Authors and Affiliations

  1. Computer Science and York Centre for Quantum Technologies, University of York, York, YO10 5GH, UK

    Stefano Pirandola, Carlo Ottaviani, Gaetana Spedalieri & Samuel L. Braunstein

  2. Department of Physics, University of Toronto, Toronto, M5S 3G4, Canada

    Christian Weedbrook

  3. Department of Mechanical Engineering and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, 02139, Massachusetts, USA

    Seth Lloyd

  4. Department of Physics, Technical University of Denmark, Fysikvej, Kongens Lyngby, 2800, Denmark

    Tobias Gehring, Christian S. Jacobsen & Ulrik L. Andersen

Authors
  1. Stefano Pirandola
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  2. Carlo Ottaviani
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Correspondence to Stefano Pirandola.

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Pirandola, S., Ottaviani, C., Spedalieri, G. et al. Reply to 'Discrete and continuous variables for measurement-device-independent quantum cryptography'. Nature Photon 9, 773–775 (2015). https://doi.org/10.1038/nphoton.2015.207

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