  The continuous-variable measurement-device-independent quantum key
distribution (CV-MDI-QKD) is a promising candidate for the immunity to
side-channel attacks, but unfortunately seems to face the limitation of
transmission distance in contrast to discrete-variable (DV) counterpart. In
this paper, we suggest a method of improving the performance of CV-MDI-QKD
involving the achievable secret key rate and transmission distance by using
zero-photon catalysis (ZPC), which is indeed a noiseless attenuation process.
The numerical stimulation results show that the transmission distance of
ZPC-based CV-MDI-QKD under the extreme asymmetric case is better than that of
the original protocol. Attractively, in contrast to the previous single-photon
subtraction (SPS)-based CV-MDI-QKD, the proposed scheme enables a higher secret
key rate and a longer transmission distance. In particular, the ZPC-based
CV-MDI-QKD can tolerate more imperfections of detectors than both the original
protocol and the SPS-based CV-MDI-QKD.
