Quantum Key Distribution (QKD) supports the negotiation and sharing of private keys with unconditional security between authorized parties. Over the years, theoretical advances and experimental demonstrations have successfully transitioned QKD from laboratory research to commercial applications. As QKD expands its reach globally, it encounters challenges such as performance limitations, cost, and practical security concerns. Nonetheless, innovations in satellite-based QKD and the development of new protocols are paving the way towards a worldwide network. In this review, we provide an overview of QKD implementations, with a focus on protocols, devices, and quantum channels. We discuss the challenges of practical QKD and explore long-haul QKD. Additionally, we highlight the future research directions that are expected to significantly advance the realization of a global QKD network.
@article{arxiv.2511.10982,
title = {Towards Global Quantum Key Distribution},
author = {Haoran Zhang and Haotao Zhu and Ruihua He and Yan Zhang and Chao Ding and Lajos Hanzo and Weibo Gao},
journal= {arXiv preprint arXiv:2511.10982},
year = {2025}
}