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Discrete and continuous variables for measurement-device-independent quantum cryptography

Nature Photonics volume 9, pages 772–773 (2015)Cite this article

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In a recent Article in Nature Photonics, Pirandola et al.1 claim that the achievable secret key rates of discrete-variable (DV) measurement-device-independent (MDI) quantum key distribution (QKD) (refs 2,3) are “typically very low, unsuitable for the demands of a metropolitan network” and introduce a continuous-variable (CV) MDI QKD protocol capable of providing key rates which, they claim, are “three orders of magnitude higher” than those of DV MDI QKD. We believe, however, that the claims regarding low key rates of DV MDI QKD made by Pirandola et al.1 are too pessimistic. Here, we show that the secret key rate of DV MDI QKD with commercially available high-efficiency single-photon detectors (SPDs) (for example, see http://www.photonspot.com/detectors and http://www.singlequantum.com) and good system alignment is typically rather high and thus highly suitable for not only long-distance communication but also metropolitan networks. In fact, the secret key rate of DV MDI QKD is only approximately two orders of magnitude away from the fundamental limit set by Takeoka et al.4 for typical metropolitan distances. The very low DV MDI QKD key rate claimed by Pirandola et al.1 is due to a combination of pessimistic assumptions of low-efficiency SPDs and rather high quantum bit error rate (QBER).

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Figure 1: Secret key rate of DV MDI QKD versus CV MDI QKD.

References

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Authors and Affiliations

  1. Research Laboratory of Electronics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, 02139, Massachusetts, USA

    Feihu Xu

  2. Department of Signal Theory and Communications, Escuela de Ingeniería de Telecomunicación, University of Vigo, Vigo, E-36310, Spain

    Marcos Curty

  3. Computational Sciences and Engineering Division, Quantum Information Science Group, Oak Ridge National Laboratory, Oak Ridge, 37831-6418, Tennessee, USA

    Bing Qi

  4. Department of Electrical & Computer Engineering, University of Toronto, Toronto, M5S 3G4, Ontario, Canada

    Li Qian & Hoi-Kwong Lo

Authors
  1. Feihu Xu
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  2. Marcos Curty
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  4. Li Qian
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  5. Hoi-Kwong Lo
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Correspondence to Feihu Xu.

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Xu, F., Curty, M., Qi, B. et al. Discrete and continuous variables for measurement-device-independent quantum cryptography. Nature Photon 9, 772–773 (2015). https://doi.org/10.1038/nphoton.2015.206

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