Study of Free‐Space Optical Quantum Network: Review and Prospectives (Adv. Sci. 36/2026)

Space-Air-Ground-Sea Integrated Quantum Network This cover artwork illustrates the blueprint of a space-air-ground-sea integrated quantum network for future global quantum connectivity. The image highlights the coordinated roles of satellites, ground stations, mobile platforms (drones, UAVs, maritime platforms), fiber links, and end users in enabling quantum communication across heterogeneous free-space and terrestrial channels. By presenting a multi-layer architecture spanning space, air, ground, and sea, the artwork captures the central theme of the Review by Zhenda Xie and co-wokrers (DOI: 10.1002/advs.202521923): the development of scalable, flexible, and wide-coverage quantum networks through the integration of different free-space platforms and their interfaces with fiber-based infrastructure.