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LAIQA: Shaping the Quantum satellite communications beyond Eagle-1

Giannis Giannoulis, Nikolaos K. Lyras, Argiris Ntanos, Aristeidis Stathis, Sousanis, A., Giorgos Mazarakis, Gustavo Castro do Amaral, Christine Satter, T. van der Veen, Bob P. F. Dirks, Lukas Achatz, Matthias Fink, Johannes Pseiner, Philip Menz, Peter Freiwang, A. Marousis, Emmanuel M. Xilouris, Spyros Basilakos, C. Willem Korevaar, Yunus Can Gültekin, Makris, N., Konstantinos Tsimvrakidis, George Theodore Kanellos, Martina Ottavi, Mauro Valeri, Athanasios D. Panagopoulos, H. Avramopoulos

Published Jan 1, 2024• 0 citations
Publisher

Abstract

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 LaiQa’s architecture presented in Figure 1, the horizon of LaiQa’s 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.

DOI
10.1117/12.3075388

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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 LaiQa’s architecture presented in Figure 1, the horizon of LaiQa’s 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 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.
A worldwide growing interest in fast and secure data communications pushes technology development along two lines. While fast communications can be realized using laser communications in fiber and free-space, inherently secure communications can be achieved using quantum key distribution (QKD). By combining both technologies in a single device, many synergies can be exploited, therefore reducing size, weight and power of future systems. In recent experiments we demonstrated quantum communications over large distances as well as between an aircraft and a ground station which proved the feasibility of QKD between moving partners. Satellites thus may be used as trusted nodes in combination with QKD receiver stations on ground, thereby enabling fast and secure communications on a global scale. We discuss the previous experiment with emphasis on necessary developments to be done and corresponding ongoing research work of German Aerospace Center (DLR) and Ludwig Maximilians University Munich (LMU). DLR is performing research on satellite and ground terminals for the high-rate laser communication component, which are enabling technologies for the QKD link. We describe the concept and hardware of three generations of OSIRIS (Optical High Speed Infrared Link System) laser communication terminals for low Earth orbiting satellites. The first type applies laser beam pointing solely based on classical satellite control, the second uses an optical feedback to the satellite bus and the third, currently being in design phase, comprises of a special coarse pointing assembly to control beam direction independent of satellite orientation. Ongoing work also targets optical terminals for CubeSats. A further increase of beam pointing accuracy can be achieved with a fine pointing assembly. Two ground stations will be available for future testing, an advanced stationary ground station and a transportable ground station. In parallel the LMU QKD source size will be reduced by more than an order of magnitude thereby simplifying its integration into future free-space optical communication links with CubeSats.
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
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) is currently the only known technique that is able to guarantee information-theoretic secure communications.While many countries have already started developing use-cases based mostly on terrestrial links, the high losses that afflict fiber-based channels make them unsuitable for very-long-distance communications.Taking the quantum networks to a national and global scale thus requires the use of satellite-based quantum communications, as the attenuation experienced by photons in space communications is order of magnitudes lower than the one that characterizes terrestrial networks.Thales Alenia Space in Italy (TAS-I) is positioning itself as a key actor in the development of the technology needed to perform space quantum communications.In this work, we present an overview of the initiatives that are currently being carried out by TAS-I, and define a roadmap whose steps are planned to take the current laboratory experimentation towards the development of a fully operational QKD constellation meant to provide secret keys on a global scale.We also describe a possible implementation of an Italian demonstrator mission based on a LEO satellite that acts as a trusted node to distribute shared keys among a certain number of ground stations; we study the effects of some major system choices and assess the overall achievable performance in terms of Secret Key Volume (SKV).
Satellite based quantum key distribution (QKD) enables the delivery of keys for quantum secure communications over long distances. Maturity of the technology as well as industrial interest keep increasing. So does the technology readiness of satellite free-space optical communications. A satellite QKD system comprises a quantum communication subsystem and a classical communication subsystem (public channel). Both are implemented with free-space optics. Thus, in satellite QKD system design, there are strong synergies that should be exploited as much as possible and lead to an all-optical satellite QKD system. In this paper, we present a system like this locating all optical channels in ITU DWDM C-band. We focus on the overall conceptual design and the setup of the optical channels for quantum and classical signal transmission. The system description addresses the breadboards of a transmitter laser terminal (Alice terminal), a receiver laser terminal, (Bob terminal), the public channel implementation, the interfaced QKD system and the deployed encryption system. The design basis for the Alice terminal is the laser terminal development OSIRISv3. The design basis for the Bob terminal is the ground station development THRUST. The later contains an adaptive optics correction to enable single mode fiber coupling. This enables the interfacing to almost arbitrary quantum receivers such as the Bob modules used in the described experiment. The public channel is composed of a bi-directional 1 Gbps IM/DD system and a MODEM that implements a proprietary waveform optimized for free-space channels. The system was experimentally analyzed in a field test in the framework of the German initiative QuNET which addresses the use case of quantum secure communication for authorities. The results of the experiment are used to model a feasible LEO satellite-ground link. Performance indicators such as quantum bit error rate and secure key rate of a potential mission are estimated analytically.