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.
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.
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.
Satellite based quantum key distribution (QKD) enables the delivery of keys for quantum secure communications over long distances. Maturity of the technology as well as industrial interest keep increasing. So does the technology readiness of satellite free-space optical communications. A satellite QKD system comprises a quantum communication subsystem and a classical communication subsystem (public channel). Both are implemented with free-space optics. Thus, in satellite QKD system design, there are strong synergies that should be exploited as much as possible and lead to an all-optical satellite QKD system. In this paper, we present a system like this locating all optical channels in ITU DWDM C-band. We focus on the overall conceptual design and the setup of the optical channels for quantum and classical signal transmission. The system description addresses the breadboards of a transmitter laser terminal (Alice terminal), a receiver laser terminal, (Bob terminal), the public channel implementation, the interfaced QKD system and the deployed encryption system. The design basis for the Alice terminal is the laser terminal development OSIRISv3. The design basis for the Bob terminal is the ground station development THRUST. The later contains an adaptive optics correction to enable single mode fiber coupling. This enables the interfacing to almost arbitrary quantum receivers such as the Bob modules used in the described experiment. The public channel is composed of a bi-directional 1 Gbps IM/DD system and a MODEM that implements a proprietary waveform optimized for free-space channels. The system was experimentally analyzed in a field test in the framework of the German initiative QuNET which addresses the use case of quantum secure communication for authorities. The results of the experiment are used to model a feasible LEO satellite-ground link. Performance indicators such as quantum bit error rate and secure key rate of a potential mission are estimated analytically.
Quantum Key Distribution (QKD) is currently the only known technique that is able to guarantee information-theoretic secure communications.While many countries have already started developing use-cases based mostly on terrestrial links, the high losses that afflict fiber-based channels make them unsuitable for very-long-distance communications.Taking the quantum networks to a national and global scale thus requires the use of satellite-based quantum communications, as the attenuation experienced by photons in space communications is order of magnitudes lower than the one that characterizes terrestrial networks.Thales Alenia Space in Italy (TAS-I) is positioning itself as a key actor in the development of the technology needed to perform space quantum communications.In this work, we present an overview of the initiatives that are currently being carried out by TAS-I, and define a roadmap whose steps are planned to take the current laboratory experimentation towards the development of a fully operational QKD constellation meant to provide secret keys on a global scale.We also describe a possible implementation of an Italian demonstrator mission based on a LEO satellite that acts as a trusted node to distribute shared keys among a certain number of ground stations; we study the effects of some major system choices and assess the overall achievable performance in terms of Secret Key Volume (SKV).
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 key distribution (QKD) has emerged as the leading approach for establishing information-theoretically secure communication links beyond the reach of terrestrial fiber networks. Over the past decade, missions ranging from the 635 kg Micius satellite to 3U CubeSats such as SpooQy-1 have demonstrated satellite-to-ground QKD, entanglement distribution, and quantum teleportation across distances exceeding 1,200 km. However, existing reviews of these missions focus primarily on quantum protocols and link layer physics, leaving the system level engineering trade offs particularly those governing platform selection, SWaP budgets, and subsystem integration largely unexamined. This paper presents a systems engineering review of space based quantum communication missions developed between 2016 and 2025. Each mission is analyzed through a unified framework encompassing link budget decomposition, payload miniaturization trends, and Acquisition, Tracking, and Pointing (ATP) architectures. A comparative SWaP analysis reveals that payload mass has decreased by approximately one order of magnitude from ~230 kg (Micius) to ~23 kg (Jinan-1) while reported quantum bit error rates have remained below 5%. The analysis identifies three critical gaps: (i) the absence of formal Multidisciplinary Design Optimization (MDO) frameworks in quantum satellite design, (ii) the lack of standardized performance metrics for cross mission comparison, and (iii) the disconnect between constellation level network studies and subsystem level hardware constraints. Based on these findings, system-level design strategies and a technology roadmap are proposed to support the transition from single-link demonstrations to scalable, constellation-ready quantum communication infrastructures.