Discrete-variable measurement-device-independent quantum key distribution suitable for metropolitan networks

We demonstrate that, with a fair comparison, the secret key rate of discrete-variable measurement-device-independent quantum key distribution (DV-MDI-QKD) with high-efficiency single-photon detectors and good system alignment is typically rather high and thus highly suitable for not only long distance communication but also metropolitan networks. The previous reservation on the key rate and suitability of DV-MDI-QKD for metropolitan networks expressed by Pirandola et al. [Nature Photon. 9, 397 (2015)] was based on an unfair comparison with low-efficiency detectors and high quantum bit error rate, and is, in our opinion, unjustified.