Satellite-based quantum communications represent a critical advancement in the pursuit of secure, global-scale quantum networks. Leveraging the principles of quantum mechanics, these systems offer unparalleled security through Quantum Key Distribution (QKD) and other quantum communication protocols. This review provides a comprehensive overview of the current state of satellite-based quantum communications, focusing on the evolution from terrestrial to space-based systems. We explore the distinct advantages and challenges of discrete-variable (DV) and continuous-variable (CV) quantum communication technologies in the context of satellite deployments. The paper also discusses key milestones such as the successful implementation of quantum communication via the Micius satellite and outlines the primary challenges, including atmospheric turbulence and the development of quantum repeaters, that must be addressed to achieve a global quantum internet. This review aims to consolidate recent advancements in the field, providing insights and perspectives on the future directions and potential innovations that will drive the continued evolution of satellite-based quantum communications.

翻译：卫星量子通信代表了构建安全全球量子网络的关键进展。这类系统基于量子力学原理，通过量子密钥分发及其他量子通信协议提供无与伦比的安全性。本文综述全面概述了卫星量子通信的现状，重点探讨从地面系统向天基系统的演进。我们深入分析了离散变量与连续变量量子通信技术在卫星部署场景下的独特优势与挑战。文章同时讨论了关键里程碑，如通过“墨子号”卫星成功实现的量子通信，并概述了为实现全球量子互联网必须解决的主要挑战，包括大气湍流和量子中继器的发展。本综述旨在整合该领域的最新进展，为卫星量子通信的未来发展方向与潜在创新提供见解与展望。