Performance improvement of unidimensional continuous-variable quantum key distribution using zero-photon quantum catalysis

Compared with symmetric Gaussian-modulated coherent state protocol, the unidimensional continuous-variable quantum key distribution (UCVQKD) only modulates one of the quadratures in phase space of coherent state, thereby simplifying its implementation. Although UCVQKD does reduce the system's complexity, its performance is reduced. In this work, we suggest an improved approach for UCVQKD using zero-photon quantum catalysis (ZPQC) technology. By taking advantage of this non-Gaussian operation, both secret key rate and maximal transmission distance of UCVQKD can be enhanced. Moreover, compared with another well-studied non-Gaussian operation, i.e., photon subtraction, ZPQC has higher success possibility, so that it would be beneficial for improving the amount of information acquired by legitimate users. Numerical simulation shows that the performance of UCVQKD can be improved by properly applying ZPQC. In particular, we find out that the performance of ZPQC-based UCVQKD outperforms that of photon subtraction-based UCVQKD, thereby providing an alternative way to better improve UCVQKD system. Furthermore, by taking finite-size effect into account, we derive more practical secure bound of ZPQC-based UCVQKD.