The ultra-secure quantum network leverages quantum cryptography to deliver unsurpassed data transfer security. In principle, the well-known quantum key distribution (QKD) achieves unconditional security, which raises concerns about the trustworthiness of 6G wireless systems in order to mitigate the gap between practice and theory. The long-distance satellite-to-ground evolving quantum network distributes keys that are ubiquitous to the node on the ground through low-orbit satellites. As the secret key sequence is encoded into quantum states, it is sent through the atmosphere via a quantum channel. It still requires more effort in the physical layer design of deployment ranges, transmission, and security to achieve high-quality quantum communication. In this paper, we first review the quantum states and channel properties for satellite-based quantum networks and long-range quantum state transfer (QST). Moreover, we highlight some challenges, such as transmissivity statistics, estimation of channel parameters and attack resilience, quantum state transfer for satellite-based quantum networks, and wavepacket shaping techniques over atmospheric channels. We underline two research directions that consider the QST and wavepacket shaping techniques for atmospheric transmission in order to encourage further research toward the next generation of satellite-based quantum networks.

翻译：超安全量子网络利用量子密码技术提供无与伦比的数据传输安全性。原则上，著名的量子密钥分发（QKD）能够实现无条件安全性，这引发了对6G无线系统可信度的关注，以弥合实践与理论之间的差距。通过低轨卫星，长距离的星地演进量子网络将密钥分发至地面节点，使其无处不在。由于秘密密钥序列被编码为量子态，它通过量子信道经由大气进行传输。为实现高质量的量子通信，仍需要在部署范围、传输和安全性的物理层设计方面付出更多努力。本文首先综述了基于卫星的量子网络及长距离量子态传输（QST）的量子态与信道特性。此外，我们重点探讨了一些挑战，例如透射率统计、信道参数估计与攻击韧性、基于卫星的量子网络中的量子态传输，以及大气信道上的波包整形技术。我们强调两个研究方向，即针对大气传输的QST与波包整形技术，以促进下一代基于卫星的量子网络的进一步研究。