Quantum Key Distribution (QKD) promises information theoretic security. However, the exponential decay of the secure key in optical fibres leads to limitations in long distance QKD distribution across fibres, which is necessary for global Quantum Networks (QNs). Satellite QKD can be used to generate keys over long distances bypassing fibre limitations and is thus a promising approach for global QNs. In this paper, we construct Mixed Integer Linear Program (MILP) models to investigate how to best connect the core fibre network to ground stations to minimise the overall network cost. We design one MILP that can provide a quantitative value for the number of satellites needed for a given configuration and one to optimise the allocation of the core network nodes to ground stations to minimise the overall network cost. We use these models to investigate different strategies to allocate satellites to ground stations during a satellite overpass, showing that allocating satellites based on the expected transmission requirements can reduce the number of satellites needed in a network by up to 40%. Furthermore, we use these models to investigate securing the Data Centre traffic in 2 networks, one local European Network and one Global Network showing costs in the optimal configuration can be up to 40% cheaper than simply connecting core network sites to their geographically closest ground station.
Quantum Key Distribution (QKD) promises information theoretic security. However, the exponential decay of the secure key in optical fibres leads to limitations in long distance QKD distribution across fibres, which is necessary for global Quantum Networks (QNs). Satellite QKD can be used to generate keys over long distances bypassing fibre limitations and is thus a promising approach for global QNs. In this paper, we construct Mixed Integer Linear Program (MILP) models to investigate how to best connect the core fibre network to ground stations to minimise the overall network cost. We design one MILP that can provide a quantitative value for the number of satellites needed for a given configuration and one to optimise the allocation of the core network nodes to ground stations to minimise the overall network cost. We use these models to investigate different strategies to allocate satellites to ground stations during a satellite overpass, showing that allocating satellites based on the expected transmission requirements can reduce the number of satellites needed in a network by up to 40%. Furthermore, we use these models to investigate securing the Data Centre traffic in 2 networks, one local European Network and one Global Network showing costs in the optimal configuration can be up to 40% cheaper than simply connecting core network sites to their geographically closest ground station.
Quantum Key Distribution (QKD) is a foundational technology for future secure communications, and several QKD networks have been already deployed and tested around the world using optical fibers. However, these networks cannot scale in size due to the inefficiency of fiber QKD networks with increasing distances, making satellite networks a major candidate for long-distance QKD networks. In satellite QKD networks, satellites and ground stations can act as trusted relays, distributing keys between satellite-ground station pairs to serve requests among ground stations. Satellite QKD networks face fundamental challenges due the time-varying nature of the connection between ground stations and satellites, caused by both the satellite’s orbital movement and fluctuating atmospheric attenuation. Thus, it is necessary to design novel schemes to dynamically allocate resources for satellite QKD networks that adapt to evolving network conditions in different time intervals. In this work, we investigate the problem of resource allocation in satellite QKD networks taking into account the changing key generation rates, calculated according to evolving weather conditions and satellite visibility. We first model the achievable key rate of connections between satellite and ground stations under different weather conditions, which is used as an input for optimization. We formulate a Mixed-Integer Linear Programming (MILP) model to allocate resources in satellite QKD networks, which decides both link assignments (i.e., deciding which ground to connect to for satellites) and the appropriate routing path for the trusted relay. In addition, the MILP models multiple timeslots and considers keys stored in the quantum key pool (QKP), allowing keys generated during low-load periods to be used later during high-load periods. Moreover, we propose to decide the link configuration with heuristic algorithms and then utilize ILP to decide the appropriate routing path for the trusted relay, which significantly reduces the execution time. The numerical results show that incorporating link configuration within the ILP achieves up to 20% more total served keys compared to heuristicbased baseline approaches, but with an execution time up to 700x longer.
Abstract Satellite-based platforms are currently the only feasible way of achieving intercontinental range for quantum communication, enabling thus the future global quantum internet. Recent demonstrations by the Chinese spacecraft Micius have spurred an international space race and enormous interest in the development of both scientific and commercial systems. Research efforts so far have concentrated upon in-orbit demonstrations involving a single satellite and one or two ground stations. Ultimately satellite quantum key distribution should enable secure network communication between multiple nodes, which requires efficient scheduling of communication with the set of ground stations. Here we present a study of how satellite quantum key distribution can service many ground stations taking into account realistic constraints such as geography, operational hours, and most importantly, weather conditions. The objective is to maximise the number of keys a set of ground stations located in the United Kingdom could share while simultaneously reflecting the communication needs of each node and its relevance in the network. The problem is formulated as a mixed-integer linear optimisation program and solved to a desired optimality gap using a state of the art solver. The approach is presented using a simulation run throughout six years to investigate the total number of keys that can be sent to ground stations.
In the field of Cryptography, Quantum Key Distribution (QKD) is an application of Quantum Information theory that obtained a great deal of attention in recent years. It allows to establish secret keys between two or more parties, in a much safer way than that implemented by classic cryptography (based on discrete logarithms and factorization of prime numbers). The most promising way of realizing a QKD network (especially over great distances) in the near future is by a constellation of satellites. This paper considers the problem of optimizing the orbits of the satellites in order to maximize the minimum key length shared in a network of ground stations over a fixed amount of time. Different networks of stations are considered and the influence of their geographical disposition on the design and the performance index is highlighted. The networks considered are: a global constellation, a regional European constellation, and two in which there are groups of stations in two different narrow bands of latitude. The effect of Inter-satellite links is then taken into account and how, in some cases, they can improve the performances. Finally the daily performance of the considered constellations are analyzed.
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.
Quantum key distribution (QKD) has attracted much attention on secure communications across global networks. QKD over satellite networks can overcome the limitations of terrestrial optical networks, such as large attenuation over long distance fiber channel and difficulty of intercontinental domain communications. Different QKD networks (around the world) can intercommunicate through quantum satellites, leading to a global quantum network in near future. This raises a new resource allocation and management problem of QKD involving multiple satellite layers and distributed ground stations. Using existing schemes, a single satellite cannot perform QKD for ground stations for the whole day. Moreover, the research problem is more challenging due to limitations of satellite coverage: limited cover time of low earth orbit (LEO) satellite, high channel losses of geostationary earth orbit (GEO) satellite, etc. To overcome these limitations, our study proposes a double-layer quantum satellite network (QSN) implemented quantum key pool (QKP) to relay keys for ground stations. We propose a new architecture of trusted-repeater-based double-layer quantum satellite networks, comprising GEO and LEO satellites. We also address the routing and key allocation (RKA) problem for key-relay services over QSNs. We propose a novel joint GEO-LEO routing and key allocation (JGL-RKA) algorithm to solve the RKA problem. Simulative results show that the proposed scheme can increase success probability of key-relay services significantly. We also present the impact of different route selections mechanisms, number of satellite links, satellite node capability, and service granularity on network performance.
Recent technological advancements in satellite based quantum communication has made it a promising technology for realizing global scale quantum networks. Due to better loss distance scaling compared to ground based fiber communication, satellite quantum communication can distribute high quality quantum entanglements among ground stations that are geographically separated at very long distances. This work focuses on optimal distribution of bipartite entanglements to a set of pair of ground stations using a constellation of orbiting satellites. In particular, we characterize the optimal satellite-to-ground station transmission scheduling policy with respect to the aggregate entanglement distribution rate subject to various resource constraints at the satellites and ground stations. We cast the optimal transmission scheduling problem as an integer linear programming problem and solve it efficiently for some specific scenarios. Our framework can also be used as a benchmark tool to measure the performance of other potential transmission scheduling policies.