Quantum communication will play a crucial role on both the terrestrial and space segments. For the deployment of future pan-European quantum communications infrastructures, several projects and missions have already kicked off to launch satellites equipped with quantum key distribution equipment. The Madrid Quantum Communication Infrastructure is based on novel network paradigms like software-defined networking. These features have been integrated into a model-driven simulator developed to be able to incorporate future scenarios involving satellite quantum communications in a flexible and evolutive approach.
Quantum communication will play a crucial role on both the terrestrial and space segments. For the deployment of future pan-European quantum communications infrastructures, several projects and missions have already kicked off to launch satellites equipped with quantum key distribution equipment. The Madrid Quantum Communication Infrastructure is based on novel network paradigms like software-defined networking. These features have been integrated into a model-driven simulator developed to be able to incorporate future scenarios involving satellite quantum communications in a flexible and evolutive approach.
Quantum Key Distribution (QKD) offers a fundamentally secure method for key exchange, grounded in the principles of quantum mechanics rather than computational complexity. As advancements in quantum computing threaten classical cryptographic systems (such as RSA) QKD presents itself as a crucial technology for future secure communications. Among the primary challenges for global-scale QKD is the limited range of optical fiber channels, making satellite-based free-space optical links an attractive alternative. QKD presents unique constraints related to the short and unreliable communication windows, due to atmospheric conditions and the presence of sunlight, which makes the real time operation of QKD constellations almost impossible. Traditional configurations offering instantaneous global coverage, such as Walker constellations, are not necessary for QKD networks and other constellation designs may be explored. In this work, we present as an alternative a two-height, single orbital plane constellation, which facilitates regular and extended inter-satellite visibility, enabling the constellation to function as a virtual trusted node and increasing network capacity and flexibility. The main technical contribution is the development of a simulation tool designed to evaluate and optimize satellite QKD constellations. The simulator allows researchers and mission planners to assess key generation rates and overall system performance, helping to reduce the risks, costs, and uncertainties involved in satellite deployment. Our approach provides a powerful framework for advancing the development of scalable and efficient global QKD networks.
With the goal of a space-based quantum network is to have satellites distribute keys between any nodes on the ground, we consider an evolved quantum network from a near-term form, in which a space-based relay, satellite executes a sequence of satellite-based quantum key distribution (SatQKD) missions, allowing any two ground nodes to have a shared secure key. Accordingly, we develop a comprehensive framework for the dynamic simulation of SatQKD and consider scheduling QKD downlink in future space-based quantum communication network. The embedding of precise orbital model including beam diffractions and atmosphere effects makes our framework more realistic. Incorporated with the local meteorological data to channel loss model, the cloud cover contribution to transmission disturbance is quantified to realize a quasi-experimental scenario. We provide a trade-off consideration between the duration available for communications and its corresponding average link loss during one orbit, which could be used to support decisions involving the locations of ground stations and the selection of the orbital parameters for a quantum satellite. Our work also shows that satellite downlink schedule could allow for the possibility to consider strategies for different SatQKD missions such as extending connection for distant ground nodes, prioritized delivery, or promoting keys utilization, which can be used as a guideline to support decisions for future satellite application.
Secure communication is essential for modern society, from financial transactions to critical infrastructure. As classical encryption faces threats from advancing computational power, quantum communication provides a fundamentally secure alternative based on physical laws.
We present QuaNTUM (Quantum Network at the Technical University of Munich), a modular and extensible quantum communication testbed enabling scalable experiments across fiber-based campus networks and satellite-ground links. The terrestrial network connects research institutions in Garching near Munich via single-mode fibers in a star topology with polarization-maintaining components, multiplexers, and time-synchronized analysis modules. Active polarization control and real-time feedback support stable qubit transmission for high-fidelity quantum key distribution and entanglement distribution.
A key feature is the integration of deterministic solid-state single-photon sources, including defects in hexagonal boron nitride and excited erbium atoms, with initial deployments on small satellites to bridge terrestrial and free-space channels. As an open-access platform, QuaNTUM enables protocol development, device benchmarking, and hybrid network research, providing a foundation for scalable quantum communication and future global quantum networks.
Abstract With the goal of a space-based quantum network is to have satellites distribute keys between any nodes on the ground, we consider an evolved quantum network from a near-term form, in which a space-based relay, satellite executes a sequence of satellite-based quantum key distribution (SatQKD) missions, allowing any two ground nodes to have a shared secure key. Accordingly, we develop a comprehensive framework for the dynamic simulation of SatQKD and consider scheduling QKD downlink in future space-based quantum communication network. The embedding of precise orbital model including beam diffractions and atmosphere effects makes our framework more realistic. Incorporated with the local meteorological data to channel loss model, the cloud cover contribution to transmission disturbance is quantified to realize a quasi-experimental scenario. We provide a trade-off consideration between the duration available for communications and its corresponding average link loss during one orbit, which could be used to support decisions involving the locations of ground stations and the selection of the orbital parameters for a quantum satellite. Our work also shows that satellite downlink schedule could allow for the possibility to consider strategies for different SatQKD missions such as extending connection for distant ground nodes, prioritized delivery, or promoting keys utilization, which can be used as a guideline to support decisions for future satellite application.
Space-based quantum communication is at a point where we will soon see satellites be launched to demonstrate complete and usable Quantum Key Distribution (QKD) links between several optical ground-stations in an industrial live environment. Therefore, and given the specificities of Quantum Communication, researchers as well as industrials need tools and models to leverage their existing classical optics heritage to design their future QKD constellations. Based on our experience of QKD at Fraunhofer IOF, we have developed a centralizing system which capitalize on our QKD models and completes it with the simulation of constellations, the atmosphere, the scheduling of operations and pointing specifications. This simulation tool is particularly aimed at system engineers, in both research and industry, to assess the performance of their envisioned quantum communication space. This tool encompasses all major design factors of a constellation and quantum channels for the simulation of quantum communication channels which includes optical systems as well as atmospheric propagation. Results are providing important inputs for the design of QKD space missions and systems as well as the expected level of possible services in a real-life environment. Our QKD models not only incorporate all systems in the quantum channel, and their design parameters from the laser source on the emitting side to the final click on the detectors on the receiving side, but also the post-processing impact and dynamic optimization of the quantum parameters to maximize the final secret key rate. Furthermore, the evolutive and modular design of the simulation tool itself makes it possible to incorporate different models for all parts of the simulation, for instance the atmosphere, the constellation propagation or the QKD protocols. This architecture makes it possible to interface with other experts of any field of this space system and incorporate their models too. Moreover, this allows for the assessment and comparison of different models and protocols on the final performance of the space QKD system. Our current implementation uses an in-house BBM92 model and is planned to incorporate further models developed at IOF on BB84, Hyperentangled QKD and High-Dimensional QKD.
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.