Non-Gaussian postselection and virtual photon subtraction in continuous-variable quantum key distribution

TL;DR

This paper introduces a non-Gaussian postselection technique to emulate photon subtraction in continuous-variable quantum key distribution, improving performance and distance without complex hardware, especially effective in low signal-to-noise scenarios.

Contribution

It proposes a virtual photon subtraction method via non-Gaussian postselection, enhancing CV QKD performance and distance while avoiding hardware imperfections.

Findings

Improved secure transmission distance in CV QKD.

Better reconciliation performance in low SNR regimes.

Feasibility of practical implementation demonstrated.

Abstract

Photon subtraction can enhance the performance of continuous-variable quantum key distribution (CV QKD). However, the enhancement effect will be reduced by the imperfections of practical devices, especially the limited efficiency of a single-photon detector. In this paper, we propose a non-Gaussian postselection method to emulate the photon substraction used in coherent-state CV QKD protocols. The virtual photon subtraction not only can avoid the complexity and imperfections of a practical photon-subtraction operation, which extends the secure transmission distance as the ideal case does, but also can be adjusted flexibly according to the channel parameters to optimize the performance. Furthermore, our preliminary tests on the information reconciliation suggest that in the low signal-to-noise ratio regime, the performance of reconciliating the postselected non-Gaussian data is better than that of the Gaussian data, which implies the feasibility of implementing this method practically.