This article envisions the concept of a ``Quantum Internet in the Sky", aiming to establish ubiquitous quantum communication links among distant nodes via free-space optical channels. Our key focus is on deploying quantum communication terminals on non-terrestrial platforms, specifically unmanned aerial vehicles and satellites, at various altitudes. By highlighting the unique characteristics of these platforms compared to terrestrial counterparts, we address inherent challenges and discuss potential solutions through meticulous system designs and analyses of typical non-terrestrial quantum communication scenarios. Finally, we illuminate the path forward by proposing essential future directions that underscore the integration of high-dimensional multipartite quantum communications with sensing, computing, and intelligence for multiple users en route to realizing a fully operational Quantum Internet.
This article envisions the concept of a ``Quantum Internet in the Sky", aiming to establish ubiquitous quantum communication links among distant nodes via free-space optical channels. Our key focus is on deploying quantum communication terminals on non-terrestrial platforms, specifically unmanned aerial vehicles and satellites, at various altitudes. By highlighting the unique characteristics of these platforms compared to terrestrial counterparts, we address inherent challenges and discuss potential solutions through meticulous system designs and analyses of typical non-terrestrial quantum communication scenarios. Finally, we illuminate the path forward by proposing essential future directions that underscore the integration of high-dimensional multipartite quantum communications with sensing, computing, and intelligence for multiple users en route to realizing a fully operational Quantum Internet.
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.
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.
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.
Quantum satellite communication (QSC) is emerging as a strategic technology for secure global networking and long-distance quantum connectivity. This review prioritizes the major challenges that still hinder large-scale deployment, including atmospheric loss, beam pointing and tracking, payload constraints, synchronization, scalability, and integration with terrestrial infrastructure. To contextualize these issues, we provide only a concise overview of the core concepts and enabling technologies behind QSC, together with representative milestones such as the Micius mission. Building on this background, the paper surveys recent advances in protocols, hybrid space--terrestrial architectures, turbulence mitigation, and AI-assisted optimization. It then examines future directions, including quantum Internet integration, daylight operation, satellite-supported repeaters, and space-based quantum computing. By centering the discussion on open technical bottlenecks and emerging research trajectories, this review aims to support researchers and engineers working toward practical and resilient QSC systems.
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.
Satellite-based quantum networks are emerging as a promising solution for the development of a global quantum internet in the near future. The ability to leverage the advantageous lower attenuation of optical signals from satellites to ground presents an exciting opportunity to establish a robust and secure quantum communication infrastructure on a global scale. By utilizing a constellation of satellites, it becomes feasible to continuously distribute high-fidelity quantum entanglements among ground stations over long distances, overcoming the limitations of traditional terrestrial-based quantum communication systems. In this article, we first provide a brief survey of existing solutions for satellite-based entanglement distribution, highlighting the various approaches and technologies that have been employed in this rapidly evolving field. We then delve into a formulated optimal entanglement distribution problem, aiming to optimize the distribution of quantum entanglement resources across the satellite network to maximize efficiency and reliability. This problem is addressed through a detailed exploration of several different methodologies and algorithms, each tailored to specific operational settings and constraints. Our experimental results confirm the efficiency of these approaches and provide valuable insights into their practical implementation and performance. Finally, we identify several key directions for further study and development in the realm of satellite-based quantum networks.