The satellite mission EAGLE-1 represents an important step towards a future pan-European secure Quantum Key Distribution (QKD) network. The public-private partnership behind the mission consists of a consortium of universities, research institutes, and companies partially funded by ESA, the European Union, and supported by national delegations. This unique combination of academic partners and industry facilitates a swift knowledge transfer from basic research to commercial application. Within the consortium, Tesat-Spacecom (TESAT) is responsible for developing and integrating the payload assembly of the low-earth orbit EAGLE-1 satellite. In addition, TESAT provides the SCOT80 laser terminal with minor adaptations for the mission. Here, we report on the status, technical aspects and TESATs contribution to the satellite-to-ground prepare-and-measure QKD mission.
The satellite mission EAGLE-1 represents an important step towards a future pan-European secure Quantum Key Distribution (QKD) network. The public-private partnership behind the mission consists of a consortium of universities, research institutes, and companies partially funded by ESA, the European Union, and supported by national delegations. This unique combination of academic partners and industry facilitates a swift knowledge transfer from basic research to commercial application. Within the consortium, Tesat-Spacecom (TESAT) is responsible for developing and integrating the payload assembly of the low-earth orbit EAGLE-1 satellite. In addition, TESAT provides the SCOT80 laser terminal with minor adaptations for the mission. Here, we report on the status, technical aspects and TESATs contribution to the satellite-to-ground prepare-and-measure QKD mission.
The EAGLE-1 mission aims to develop Europe's first sovereign, end-to-end space-based quantum key distribution (QKD) system. The mission is led by the European Space Agency (ESA) and SES in collaboration with several European National Space Agencies and private partners. The state-of-the-art QKD system will consist of a payload on board the EAGLE-1 low Earth orbit (LEO) satellite, optical ground stations, quantum operational networks, and key management system. The EAGLE-1 mission represents a major step for next-generation quantum communication infrastructures, delivering valuable technical results and mission data. The Institute of Communications and Navigation (IKN) of the German Aerospace Center (DLR) is a key partner in the EAGLE-1 mission and is involved in the research and development of elements in both space and ground segments. Here we report on the development of the QKD transmitter, a vital part of the QKD payload, and the customization of the Optical Ground Station Oberpfaffenhofen (OGS-OP) to conduct the IOT phase of EAGLE-1. For the space segment, DLR-IKN is in charge of the design of the QKD transmitter, including the development of the software and firmware. This transmitter generates quantum states which are used to implement a QKD protocol based on an optical signal, that will be transmitted to ground. For the ground segment, The OGS-OP will serve as the in-orbit testing ground station for EAGLE-1. Building upon the expertise with a range of satellites for quantum communication, as well as new implementations, OGS-OP will validate the performance of the payload, optical link and QKD system for the first time. We present the main developments of OGS-OP for the mission, which includes the implementation of an upgraded adaptive optics system to correct for atmospheric distortions and optimize the coupling of the incoming light into a single mode optical fiber.
Eagle-1 satellite which is currently under development, by a consortium of over 20 European (EU) companies, will be the first space-based EU Quantum Key Distribution (QKD) system providing symmetrical quantum keys via the implementation of Prepare & Measure (P&M)-QKD links and is expected to be launched in late 2025. In parallel to this Eagle-1 milestone for European satellite-QKD networks, the European space quantum engineering community should work in parallel on the development of space-QKD components offering in the short-term even higher Key Performance Indicators (KPIs) to meet the demand for high secure key rates, in the middle-term to introduce space-QKD components for system designs and architectures beyond the horizon of Eagle-1, and in the longer term to prepare for the future quantum space internet. LaiQa (Leap in Advancing of crItical Quantum key distribution-spAce components - http://www.laiqahorizon.eu/) project is a collective effort of 8 partners funded by Horizon Europe launched in January 2024, and it aims to come as a pragmatic innovation action addressing the satellite QKD landscape beyond the Eagle-1 milestone, bringinginnovations across different timescales for the EU roadmap of satellite quantum communications. LaiQa will bring to the space-QKD ecosystem 1550 nm space-qualified Decoy-State (DS)-BB84 source for polarization-encoded Prepare & Measure (P&M)-QKD sources in architectures based on trusted satellites. As illustrated in LaiQas architecture presented in Figure 1, the horizon of LaiQas development path goes beyond the standard P&M-based QKD components, since it will pursue the development of a space-deployable high-brightness 1550 nm entangled photon pair source (EPPS). Apart from the novel space implementations, LaiQa aims to accelerate the quantum readiness level of the ground terminals operated as trusted nodes by delivering advanced adaptive optics and fiber-coupling systems for 1550 nm photons, to fully exploit the available fiber-based terrestrial European Quantum Communication Infrastructure (Euro-QCI) segments. Moving towards satellite quantum information networks for applications beyond QKD, LaiQa will bring Photonic Integrated Circuit (PIC)-based implementations for generating photon-pairs which will be combined with novel quantum memory blocks enabling quantum repeater technology, and thus, long-distance entanglement distribution to quantum processing nodes. This concept paper describes the vision, architecture, and implementation aspects of the EU-funded LaiQa project. Preliminary KPIs of LaiQa quantum space technological blocks will be presented and preliminary feasibility analysis for the overall architecture will also be discussed. The demonstration aspects will be also discussed since LaiQa technologies are intended to be deployed over two advance test infrastructures including 2.5 km terrestrial Free Space Optical (FSO)-QKD links and real field deployments in Helmos Optical Ground Station (OGS) in Greece.
The EAGLE-1 mission aims to deliver Europe’s first autonomous space based quantum key distribution (QKD) system launching the EAGLE-1 satellite in 2026. A key element of this demonstration mission is the development and space qualification of a QKD transmitter, essential for enabling secure quantum communications. This paper presents the subsystem-level design, component qualification, system calibration, and functional testing of the QKD transmitter developed by the Institute of Communications and Navigation (KN) of the German Aerospace Center (DLR). The QKD transmitter is responsible for converting quantum key information into an optical signal for transmission to ground. The quantum key and QKD protocol is based on a quantum random number generator (QRNG) and the key bits are encoded in single photons. The transmitter hardware consists of various electrical and optical components, including modulators, attenuators, amplifiers, and passive elements. We discuss component selection criteria, as well as vibration and shock testing to verify launch resilience and thermal vacuum testing to assess operational stability under space conditions. One of the key challenges is the time and bias drift of critical components, which occurs after system boot-up and varies with temperature and time. These drifts directly affect the timing, amplitude, and phase of the optical signal, impacting overall QKD performance. We present the design of the calibration methodologies which ensure autonomous calibration of the transmitter in orbit, which provides the system stability required to adhere to the QKD protocol requirements. Finally, we describe the laboratory tests assessing quantum bit error rates (QBER).
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), a novel cryptographic technique for secure distribution of secret keys between two parties, is the first successful quantum technology to emerge from quantum information science. The security of QKD is guaranteed by fundamental properties of quantum mechanical systems, unlike public-key cryptography whose security depends on difficult to solve mathematical problems such as factoring. Current terrestrial quantum links are limited to about 250 km. However, QKD could soon be deployed on a global scale over free-space links to an orbiting satellite used as a trusted node. \n \nEnvisioning a photonic uplink to a quantum receiver positioned on a low Earth orbit satellite, the Canadian Quantum Encryption and Science Satellite (QEYSSat) is a collaborative project involving Canadian universities, the Canadian Space Agency (CSA) and industry partners. This thesis presents some of the research conducted towards feasibility studies of the QEYSSat mission. \n \nOne of the main goals of this research is to develop technologies for data acquisition and processing required for a satellite-based QKD system. A working testbed system helps to establish firmly grounded estimates of the overall complexity, the computing resources necessary, and the bandwidth requirements of the classical communication channel. It can also serve as a good foundation for the design and development of a future payload computer onboard QEYSSat. \n \nThis thesis describes the design and implementation of a QKD post-processing system which aims to minimize the computing requirements at one side of the link, unlike most traditional implementations which assume symmetric computing resources at each end. The post-processing software features precise coincidence analysis, error correction based on low-density parity-check codes, privacy amplification employing Toeplitz hash functions, and a procedure for automated polarization alignment. \n \nThe system's hardware and software components integrate fully with a quantum optical apparatus used to demonstrate the feasibility of QKD with a satellite uplink. Detailed computing resource requirements and QKD results from the operation of the entire system at high-loss regimes are presented here.
Quantum key distribution (QKD) is a cryptographic method enabling two parties to establish a private encryption key. The range of communication of ground-based QKD is limited to an order of 100km, due to in-fibre attenuations and atmospheric losses, and the development of quantum repeaters remains technologically challenging. While trusted-node links make communication over large distances possible, satellite-QKD is required for communication over global distances. By using satellites equipped with high-quality optical links, satellite-QKD can achieve ultra-long-distance quantum communication in the 1000-km range. The significant potential of satellite-QKD for the creation of global quantum networks thus makes it a particularly interesting field of research. In this analysis, we begin with an overview of the technical parameters of performing satellite-QKD, including infrastructure and protocols. We continue with a high-level summary of advancements in satellite-QKD by analysing past, present and proposed satellite-QKD missions and initiatives around the world. We conclude by discussing the technical challenges currently faced in satellite-QKD, which can be tackled through future research in this area.