Quantum Key Distribution (QKD) has emerged as a revolutionary technique for ensuring unconditional secure communication between two parties by exploiting the fundamental principles of quantum mechanics. At present, satellite based QKD is the only choice for distributing secure keys over larger distances, as fiber-based and terrestrial free-space systems have limited range. In this paper, the system engineering study and performance analysis for the satellite based QKD system is presented by carrying out the simulations for different orbits and orbital parameters. This work also presents the methodology to estimate the quantum keys generated for satellite to ground scenario across some of the suitable locations across Indian mainland. The orbital parameters of a LEO orbit are optimized to obtain a required accumulated key of more than 1 Mbits per day across all the ground stations. Two standard operating wavebands viz. 785 nm and 1550 nm, most suitable for quantum communication, are considered for both daylight and eclipse conditions and the difference in accesses, access gaps, access duration, key generation and key accumulation is obtained. A typical use-case scenario analysis for utilization of accumulated key over a year is also presented.
Quantum Key Distribution (QKD) has emerged as a revolutionary technique for ensuring unconditional secure communication between two parties by exploiting the fundamental principles of quantum mechanics. At present, satellite based QKD is the only choice for distributing secure keys over larger distances, as fiber-based and terrestrial free-space systems have limited range. In this paper, the system engineering study and performance analysis for the satellite based QKD system is presented by carrying out the simulations for different orbits and orbital parameters. This work also presents the methodology to estimate the quantum keys generated for satellite to ground scenario across some of the suitable locations across Indian mainland. The orbital parameters of a LEO orbit are optimized to obtain a required accumulated key of more than 1 Mbits per day across all the ground stations. Two standard operating wavebands viz. 785 nm and 1550 nm, most suitable for quantum communication, are considered for both daylight and eclipse conditions and the difference in accesses, access gaps, access duration, key generation and key accumulation is obtained. A typical use-case scenario analysis for utilization of accumulated key over a year is also presented.
Quantum Key Distribution (QKD) is a revolutionary technology which leverages the laws of quantum mechanics to distribute cryptographic keying material between two parties with theoretically unconditional security. Terrestrial QKD systems are limited to distances of <;200 km in both optical fiber and line-of-sight free-space configurations due to severe losses during single photon propagation and the curvature of the Earth. Thus, the feasibility of fielding a low Earth orbit (LEO) QKD satellite to overcome this limitation is being explored. Moreover, in August 2016, the Chinese Academy of Sciences successfully launched the world's first QKD satellite. However, many of the practical engineering performance and security tradeoffs associated with space-based QKD are not well understood for global secure key distribution. This paper presents several system-level considerations for modeling and studying space-based QKD architectures and systems. More specifically, this paper explores the behaviors and requirements that researchers must examine to develop a model for studying the effectiveness of QKD between LEO satellites and ground stations.
Quantum key distribution (QKD), the technology to generate distant secure keys for later usage in secure communication, has become a mature topic since the 1980s. While terrestrial QKD over fiber networks is suitable for short-distance urban networks, QKD via satellites promises to gap the distance requirement on a global scale that limits terrestrial QKD. Satellite QKD requires the exchange of quantum states between a satellite and multiple ground stations. The goal is then to facilitate shared secret keys between the ground stations, which can then be relayed to users near the ground stations. The satellite usually carries the quantum sources as its payload and sends them to the ground station via a downlink. The QKD protocol is heavily influenced by the choice of the quantum source, with typically one of two types: approximate single photon source (such as a weak laser) or an entangled source. Similarly, the ground station must be equipped to receive, measure and process the quantum signals sent by the satellite. Although there are also reverse schemes, where the satellite acts as the receiver and the ground station as the sender, these schemes are less explored due to higher noise in the uplink and less engineering experience. As with any system containing a high heterogeneity, many different implementation schemes lead to a variety of optimized use cases based on different criteria. Satellite QKD carries the further complication that it must be adapted to international standards. In this paper we present different satellite and ground station architectures that lean on the developments in the projects EAGLE-1, QUBE, QuNET, RoGloQuaN, addressing different protocols, sources, satellite sizes and telescope sizes. We also discuss the need for agility and configuration of components in a heterogeneous environment.
Security is a major concern of digital society, and quantum key distribution (QKD) can contribute with an un-conditional secure mechanism for symmetric key distribution. Satellites have the opportunity to overcome the range limit of quantum communications based on fiber networks. This paper presents a method for performance evaluation of QKD based on satellites, exemplified with a case study that considers small satellites (CubeSats) in low Earth orbits (LEO), to illustrate a flexible configuration of the quantum range extender use case. To the best of the authors’ knowledge, this is the first time that a system evaluation derived from orbital propagation data is conducted while also considering QKD with a finite key statistics approach. This evaluation aims to match with the shortness and variability of visibility intervals typical of LEO orbits. The results confirm the feasibility of proposed case study and show the impact of relevant systems and orbital parameters in the key generation performance, such as system characteristics, uplink or downlink configuration, satellite altitude and orbital inclination. The estimated performance is then scaled to a year along with some sensitivity scenarios. The presented results may guide the design of future QKD satellite mission proposals.
Optical quantum communication utilizing satellite platforms has the potential to extend the reach of quantum key distribution (QKD) from terrestrial limits of ∼200 km to global scales. We have developed a thorough numerical simulation using realistic simulated orbits and incorporating the effects of pointing error, diffraction, atmosphere and telescope design, to obtain estimates of the loss and background noise which a satellite-based system would experience. Combining with quantum optics simulations of sources and detection, we determine the length of secure key for QKD, as well as entanglement visibility and achievable distances for fundamental experiments. We analyse the performance of a low Earth orbit satellite for downlink and uplink scenarios of the quantum optical signals. We argue that the advantages of locating the quantum source on the ground justify a greater scientific interest in an uplink as compared to a downlink. An uplink with a ground transmitter of at least 25 cm diameter and a 30 cm receiver telescope on the satellite could be used to successfully perform QKD multiple times per week with either an entangled photon source or with a weak coherent pulse source, as well as perform long-distance Bell tests and quantum teleportation. Our model helps to resolve important design considerations such as operating wavelength, type and specifications of sources and detectors, telescope designs, specific orbits and ground station locations, in view of anticipated overall system performance.
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.
Satellite-based Quantum Key Distribution (QKD) is emerging as a cornerstone technology for secure global communication networks, extending quantum-safe key exchange beyond the limitations of terrestrial fiber systems. Achieving scalable and robust space-to-ground QKD links requires careful optimization of optical terminals, channel conditions, and protocol-specific parameters.In this work, we present a system-level analysis of design priorities for satellite QKD networks, using realistic atmospheric conditions modeled with MODTRAN 6 and a simulation tool designed and developed in-house. For discrete-variable (DV) QKD, we analyze how the secret key rate (SKR) varies with satellite altitude for two telescope aperture sizes under representative rural and urban ground station scenarios. Results show that DV-QKD enables secure key distribution over distances compatible with LEO and MEO satellite links when using moderately sized ground telescopes (600mm and 800mm apertures). For continuous-variable (CV) QKD with Gaussian modulation, SKR is analyzed as a function of satellite altitude under the most favorable link conditions identified in the DV-QKD study (800 mm ground aperture and rural environment), indicating that CV-QKD is feasible for secure key exchange with low-altitude LEO satellites, as long as the excess noise remains within low (yet experimentally achievable) levels (≈ 0.045 SNR). Additionally, we establish upper bounds on tolerable excess noise via heatmap analysis, defining the operational regime for secure CV-QKD.These findings provide quantitative guidance for designing scalable, interoperable, and cost-efficient space-to-ground QKD infrastructures, supporting the development of robust global quantum communication networks.