  In this paper, we analyse the role of non-Gaussianity in continuous-variable
(CV) quantum key distribution (QKD) with multimode light under mode-mismatch.
We consider entanglement-based protocol with non-Gaussian resources generated
by single-photon-subtraction and zero-photon-catalysis on a two-mode squeezed
vacuum state (TMSV). Our results indicate that, compared to the case of TMSV,
these non-Gaussian resources reasonably enhances the performance of CV-QKD,
even under the effect of noise arising due to mode-mismatch. To be specific,
while in the case of TMSV the maximum transmission distance is limited to 47
Km, single-photon subtracted TMSV and zero-photon-catalysed TMSV yield much
higher distance of 73 Km and 152 Km respectively. However, photon loss as a
practical concern in zero-photon-catalysis setup limits the transmission
distance for zero-photon-catalysed TMSV to 36 Km. This makes
single-photon-subtraction on TMSV to be the best choice for entanglement-based
CV-QKD in obtaining large transmission distance. Nonetheless, we note that the
non-Gaussianity does not improve the robustness of entanglement-based CV-QKD
scheme against detection inefficiency. We believe that our work provides a
practical view of implementing CV-QKD with multimode light under realistic
conditions.
