Overview of applications of heralded single photon source in quantum key distribution

In this paper, we mainly introduce the preparation and physical properties of the heralded single-photon source, the development history and its applications in three typical quantum key distribution protocols, including BB84, measurement-device-independent and twin-field quantum key distribution protocols. Moreover, we make comparisons of the above quantum key distribution protocols between using heralded single-photon source and using weak coherent sources, and analyze their advantages and disadvantages. Besides, according to the characteristics of single-photon interference in twin-field quantum key distributions, the limitations of separately applying heralded single-photon sources to twin-field quantum key distributions are revealed, and possible solutions are discussed. Therefore, this work may provide valuable references and help for the practical implementation of quantum secure communication in the near future.