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.
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.
The optical quantum network plays an important role in quantum information technology, enabling important applications including quantum communication, distributed quantum computing, quantum remote sensing, etc. Without the fiber connection limitation, free-space quantum network is free from fiber scattering loss, and enables more flexible quantum network connections. In recent years, rapid progress has been achieved in free-space quantum networks using fixed ground stations, satellites, and mobile platforms. Fixed ground stations are the primary testbeds for free-space experiments, and link distances of up to 144 km have been demonstrated between selected locations. Satellites, free from atmospheric turbulence and absorption, further boost the distance to over a thousand kilometers, enabling intercontinental connections. Besides fixed ground stations and satellites, mobile platforms offer highly flexible connections to end users, as fully presented using drones, after preliminary works using balloons, aircraft, helicopters, etc. Here we review the free-space experiments based on these three platforms, and analyse and compare their characteristics, advantages, and limitations in different scenarios, respectively. In the prospectives, we discuss their unique and complementary roles, and the key challenges and enabling technologies toward the ultimate goal of a practical quantum network, in conjunction with the fiber-based quantum network.
Remarkable achievements have been witnessed in free-space quantum key distribution (QKD), which acts as an available approach to extend the transmission range of quantum communications.The feasibility of transmitting qubits through the free-space channel with the aid of moving platforms like satellites, aircraft, unmanned aerial vehicles (UAVs) has been verified.In view of the limited working time and resource consumption of the satellite-based QKD and the last-mile challenges of connecting satellite nodes with terrestrial networks, the airborne QKD is expected to provide flexible and relay links for the large-scale integrated network.This paper reviews the recent significant progress of QKD based on aircraft or UAVs, highlights their critical techniques, and prospects the future of airborne quantum communications.
Satellites and aerial platforms can be significant in the development of new telecommunications networks, allowing to deploy networks with extremely high performance even in remote areas. Recently, considering the development of quantum communication technologies, many studies are concentrated on Free Space Optic (FSO) Non-Terrestrial links, also considering that the studies performed so far on Optical Fibers (OFs) have not pointed out significant results, especially in terms of coverage. Moreover, the decrease of launch costs and the use of new satellite technologies such as CubeSats make the deployment of satellite constellations affordable. Thanks to the deployment of Non-Terrestrial Quantum Networks (NTQNs), the novel services offered by the Quantum Internet (QI) could be made easily accessible to all. In particular, Quantum Computers (QCs) can perform beyond the capabilities of any classical processor, and the interconnection of these devices on a global scale makes it possible to achieve extremely high computational capabilities, thus opening the way to new applications, such as Quantum Cloud (QCloud). Therefore, the recent studies in this area motivate this survey, which in addition to providing some base concept of quantum information, describes the current technologies needed to create quantum NT backbones. Specifically, this survey examines some studies over the period 2010–2023, which are related to the realization of quantum communications using satellites and other aerial platforms such as High Altitude Platforms (HAPS) and quantum drones. Some of the architectures that are described in this survey make use of the Software-Defined Networking (SDN) paradigm, which can be envisaged as a key enabler for the management of heterogeneous QNs in general. Furthermore, through the description of various experiments, the paper shows the applications that can be enabled by the future quantum NT backbones. In particular, in addition to improving the security of current systems through the Quantum Key Distribution (QKD), it could be possible to interconnect clusters of QCs over long distances and create extremely reliable positioning systems. Finally, the paper outlines some possible future developments.
This article will explore the design and implementation of quantum networks in space integrated with quantum networks on Earth. We propose a three-layer approach, involving GEO and LEO satellites integrated with terrestrial ground stations. We first analyze the channel conditions between the three layers, and then highlight the key role of LEO satellites in the integrated space-terrestrial system – namely the source of entanglement distribution between specified terrestrial stations via direct downlink quantum-optical channels. The GEO satellites in the considered system are used primarily as “coordination” stations, managing and directing the LEO satellites regarding the positioning and timing of entanglement distribution. Complexity, in the form of entanglement distillation and quantum-state correction, is concentrated at the terrestrial stations, and teleportation is used as the primary quantum channel in the LEO uplinks and the inter-terrestrial channels. Although our designs are futuristic in that they assume limited quantum memory at the transceivers, we also discuss some near-term uses of our network in which no quantum memory is available.
In the upcoming 6G era, existing ground networks have evolved toward space-air-ground integrated networks (SAGIN), providing ultra-high data rates, seamless network coverage, and ubiquitous intelligence for communications of applications and services. However, conventional communications in SAGIN still face data confidentiality issues. Fortunately, the concept of Quantum Key Distribution (QKD) over SAGIN is able to provide information-theoretic security for secure communications in SAGIN with quantum cryptography. Therefore, in this article, we propose quantum-secured SAGIN (Q-SAGIN) which are feasible to achieve proven secure communications using quantum mechanics to protect data channels between space, aerial, and ground nodes. Moreover, we propose a universal QKD service provisioning framework to minimize the cost of QKD services under the uncertainty and dynamics of communications in Q-SAGIN. In this framework, fiber-based QKD services are deployed in passive optical networks with the advantages of low loss and high stability. Moreover, the widely covered and flexible satellite-and UAV-based QKD services are provisioned as a supplement during the real-time data transmission phase. Finally, to examine the effectiveness of the proposed concept and framework, a case study of Q-SAGIN in the Metaverse is conducted where uncertain and dynamic factors of the secure communications in Metaverse applications are effectively resolved in the proposed framework.
In recent years, fiber-based quantum key distribution systems have emerged in a growing number of sectors. However, fiber optic links limit the distance that can be covered in point-to-point connections, so developments in free-space quantum communications are important. These can be used to establish free-space QKD links between buildings or to connect remote ground stations using satellite systems. In our research, we are developing an entanglement-based free-space QKD system based and we are simulating quantum communication satellite systems based on entanglement.