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International Conference on Space Optics (ICSO)

GEOQKD: quantum key distribution from a geostationary satellite

Bob P. F. Dirks, Ivan Ferrario, Alessandro Le Pera, Daniele Vito Finocchiaro, Marine Desmons, Dorus de Lange, Harry de Man, Arjan J. H. Meskers, Jaco P. J. Morits, Niels M. P. Neumann, Rudolf Saathof, Gert Witvoet

Published Jun 11, 2021• 16 citations
Publisher

Abstract

Due to the distance limitation of quantum communication via ground-based fibre networks, space-based quantum key distribution (QKD) is a viable solution to extend such networks over continental and, ultimately, over global distances. Compared to LEO, QKD from GEO would offer substantial advantages, i.e. large coverage, continuous link to ground stations (cloud cover limited), 24/24h operation (background limited), no tracking required, however, coming with large link losses seen the space-ground distance. TNO, together with Eutelsat and CGI-NL, performed a detailed study on the feasibility of QKD from GEO, including a high level system design of payload and ground segment. We conclude that QKD from GEO is technically feasible, and a favourable solution if the satellite needs to act as an untrusted node (that is, no security assumptions required for the space segment). However, the optimal solution, generating a higher value-for-money, is to use a hybrid system, implementing an untrusted and trusted mode BBM92 QKD protocol. In order to arrive at a minimum required secure bit rate of ~1 bit/s in untrusted mode, a 2x ~0.5m diameter telescope in the space segment is required with <0.25µrad pointing accuracy, a <1GHz entangled photon source, in combination with ~2m diameter telescopes on ground. Details on our assumptions and results and drawings of the high level system design will be presented, as well as the development roadmap describing the required technology improvements and building blocks for the overall hybrid approach, which is applicable to non-GEO applications as well.

DOI
10.1117/12.2599164

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Due to the distance limitation of quantum communication via ground-based fibre networks, space-based quantum key distribution (QKD) is a viable solution to extend such networks over continental and, ultimately, over global distances. Compared to LEO, QKD from GEO would offer substantial advantages, i.e. large coverage, continuous link to ground stations (cloud cover limited), 24/24h operation (background limited), no tracking required, however, coming with large link losses seen the space-ground distance. TNO, together with Eutelsat and CGI-NL, performed a detailed study on the feasibility of QKD from GEO, including a high level system design of payload and ground segment. We conclude that QKD from GEO is technically feasible, and a favourable solution if the satellite needs to act as an untrusted node (that is, no security assumptions required for the space segment). However, the optimal solution, generating a higher value-for-money, is to use a hybrid system, implementing an untrusted and trusted mode BBM92 QKD protocol. In order to arrive at a minimum required secure bit rate of ~1 bit/s in untrusted mode, a 2x ~0.5m diameter telescope in the space segment is required with <0.25µrad pointing accuracy, a <1GHz entangled photon source, in combination with ~2m diameter telescopes on ground. Details on our assumptions and results and drawings of the high level system design will be presented, as well as the development roadmap describing the required technology improvements and building blocks for the overall hybrid approach, which is applicable to non-GEO applications as well.
Quantum Key Distribution (QKD) is the most mature quantum technology, having achieved on-ground applications and commercially available products.In this domain, satellite platforms are essential to achieve a communication range reaching the intercontinental scale, acting thus as enablers for the future global quantum internet operation.This paper will report on the main results of the TNO-Eutelsat-TAS Italy project aiming to evaluate a novel hybrid approach for improved QKD performance particularly suited for geostationary orbits (GEO); the Dutch TKI HTSM sponsors the overall activity.We will present the results of lab-based tests of a novel QKD free-space approach that simultaneously implements the BBM92 protocol in both trusted and trust-free mode, following a joint Eutelsat-TNO patent.The trust-free mode between two ground receivers is the standard BBM92 protocol that uses entangled photons and there is no need for further security assumptions on the satellite payload.In trusted mode operation, one of the two entangled photons is measured directly on board.Key material is generated between ground and satellite.Security measures will be needed in the space segment, which therefore needs to be trusted.Further, we will present a demonstration roadmap aiming at free space field test to validate loss and key rate models for a free space link up to 2.5km in one of the arms.We also present a perspective on potential future GEO-based quantum applications beyond QKD.
Abstract In pursuit of a global quantum key distribution (QKD) network, a service based on untrusted nodes on geostationary satellites could offer wide coverage, continuous operation, and enhanced security compared to the trusted node alternative. Although this scenario has been studied for entanglement-based protocols, such an approach would require large-area telescopes both on the ground and in space. In this work, we analyze the performance of two QKD protocols well adapted to this scenario, namely twin-field (TF) and mode-pairing (MP) QKD, which exhibit high resilience to high-loss channels. Leveraging an in-depth simulation of communication channels corrected with adaptive optics, we assess the expected secret key rates for both protocols in a configuration involving two 50 cm telescopes on board the satellite and ground-based telescopes ranging from 20 cm to 1 m in aperture. Our results show that, in the best case and considering realistic detectors, it is possible to achieve secret key rates on the order of a few 100 bit s −1 for both TF and MP-QKD. We show, notably, that secret key generation is potentially feasible even with 20 cm ground telescopes, highlighting the high scalability potential of such a configuration.
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.
The usage of QKD protocols through the current terrestrial infrastructure is limited to a hundred kilometers due to attenuation problems with fiber. This implies that the satellite will be necessary for the transmission of quantum keys in order to avoid these terrestrial limitations. Therefore, the current debate does not lie in the need for the satellite but rather in what type of infrastructure will be best suited, and specifically the usage of GEO vs LEO satellites. This analysis is not trivial and should not consider only the link budgets and the physical layer as it has been done up to date. It should also consider even more important factors, as the service KPIs that the end user will request such as key rate, availability, security of the keys and their maintenance, etc., as well as the possible communications architectures to provide the service. Therefore, the analysis should introduce the market oriented component, and provide the optimal solutions based on the scenarios and requirements requested by the customer. In this frame, and under ESA ARTES funding, a Spanish consortium led by Hispasat is defining an operational GEO QKD mission that shall fly as hosted payload in 2025. The quantum communications payload proposed in this mission represents a step beyond the state of the art since it is the first implementation of a quantum key distribution channel from geostationary orbit. This new service will involve the implementation of a complete communications system not currently available that will require the development of new technological elements and the adaptation for their operation in space of technologies such as photon sources, telescopes for optical communications compatible with quantum state transmission or processors for the distillation of quantum keys, as well as a whole new ground segment to control and manage the new quantum key distribution service and its integration into a future European secure quantum communications network. Details of the challenges and approach of this mission shall be presented
We present a mission proposal to provide a space based quantum key distribution service. Using entangled photon pairs distributed to two ground stations with a simultaneous double downlink establishes a secret key directly at the user locations. The satellite and the payload do not generate or process any secret key information and the security design, certification and operation of the key management can be restricted to the user locations on ground. Positioning the satellite in GEO enables covering Europe and intercontinental connections, allows flexible service planning to cope with weather constraints and removes the need for coarse tracking telescopes in space and on ground while allowing long integration times. The large link distance and the combined losses of two down links require large optical terminals in space and on ground to obtain a usable secure key generation rate. We will present results from an ESA internal Phase 0 study concentrating on the payload design and performance.
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.