Documentation for version 1.1 of the open-source software SatQuMA: Satellite Quantum Modelling & Analysis. We provide a numerical key rate analysis, which determines the amount of expected key generation in satellite-based quantum key distribution protocols. This key length analysis will help develop an intuition on the effects of different operational scenarios on the key rate and inform the development of source and receiver systems. This numerical toolkit will provide a guide to future satellite missions.
Documentation for version 1.1 of the open-source software SatQuMA: Satellite Quantum Modelling & Analysis. We provide a numerical key rate analysis, which determines the amount of expected key generation in satellite-based quantum key distribution protocols. This key length analysis will help develop an intuition on the effects of different operational scenarios on the key rate and inform the development of source and receiver systems. This numerical toolkit will provide a guide to future satellite missions.
Developing global quantum communication networks is integral to the realisation of the quantum internet, which is expected to impart a similar revolutionary impact on the technological landscape as the classical internet. Satellite-based quantum communications provides a practical route to global quantum networking. In this work, we model finite statistics to determine the finite secret key length generation in SatQKD systems that implement trusted-node downlink operation with weak coherent pulse sources. We optimise the finite key rate for different practical operations and determine the key generation footprints. Our work provides an essential guide for future satellite missions to establish performance benchmarks for both sources and detectors.
Quantum Key Distribution (QKD) is a potential mitigation against quantum computation advances that threaten currently deployed public key cryptosystems. QKD is also a precursor to large-scale quantum communications and the quantum internet. Terrestrial direct transmission of quantum photonic signals is restricted by optical fibre exponential absorption, hence space-based systems have been proposed for intercontinental distribution of quantum keys with lower-loss free-space transmission through vacuum. However, challenges remain for the practical deployment of satellite QKD (SatQKD) such as weather, background light, and terminal deployment. In particular, the short transmission time inherent in low Earth orbit satellite QKD and finite statistical uncertainty can limit secure key generation. Here we illustrate the analysis of these effects and some practical engineering design and operational constraints on key length using the Satellite Quantum Modelling and Analysis (SatQuMA) software package being developed for satellite quantum communications research.
Abstract The goal of the space-based quantum network is to form the backbone of the quantum internet for long-distance secure data transfer, networked distributed quantum information processing, and other applications. Consider that the quantum network evolved from a recent form where a satellite performs a sequence of satellite-to-ground quantum key distribution (SatQKD) missions that allow any two ground nodes to have the symmetric encryption keys, we here develop a framework for the SatQKD downlink modelling and scheduling analysis. Incorporated with the orbital calculation and the meteorological data to downlink SatQKD modelling, the dynamic characteristics of the satellite-to-ground optical transmission could be simulated. Our work shows that the satellite downlink scheduling allows for the possibility to consider different strategies for SatQKD missions such as extending connection for distant ground nodes, prioritized delivery and promoting keys utilization, which may guide design and analysis of future missions for future satellite application.
Abstract Global quantum communications will enable long-distance secure data transfer, networked distributed quantum information processing, and other entanglement-enabled technologies. Satellite quantum communication overcomes optical fibre range limitations, with the first realisations of satellite quantum key distribution (SatQKD) being rapidly developed. However, limited transmission times between satellite and ground station severely constrains the amount of secret key due to finite-block size effects. Here, we analyse these effects and the implications for system design and operation, utilising published results from the Micius satellite to construct an empirically-derived channel and system model for a trusted-node downlink employing efficient Bennett-Brassard 1984 (BB84) weak coherent pulse decoy states with optimised parameters. We quantify practical SatQKD performance limits and examine the effects of link efficiency, background light, source quality, and overpass geometries to estimate long-term key generation capacity. Our results may guide design and analysis of future missions, and establish performance benchmarks for both sources and detectors.
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.
Establishing information-theoretically secure communication between arbitrary locations on Earth is a central goal of quantum networking, for which space-based distribution of quantum entanglement is a leading approach. Modelling and analysis of the performance of satellite entanglement pair distribution is therefore important for the architecture and design of future constellations and space systems. However, entanglement-based quantum key distribution in the absence of quantum repeaters, is especially prone to finite-key effects due to low coincident count rates compared to trusted-node single-path links. Quantifying these effects under realistic orbital conditions is therefore essential for the design of practical satellite quantum communication systems. Here, we develop a high-fidelity model of pair distribution from a low-Earth-orbit satellite that captures orbital dynamics, elevation-dependent loss, background noise, and extraneous detector effects. Integrating this with a finite-key security framework for the BBM92 protocol, we optimise the secret key length across different overpass geometries, orbital altitudes, and optical ground station (OGS) separations. We show that secure key generation remains feasible in early clear daytime conditions using baseline parameters representative of current technologies, while showing that modest system improvements could further extend daytime operation. Finally, we evaluate the annual secret key performance for representative intercity-scale OGS pairings. Our results provide quantitative performance bounds and practical design guidelines for near-term entanglement-based satellite QKD, enabling informed trade-offs between satellite payload complexity, ground infrastructure, and achievable secure key throughput.