LaiQa: Shaping the Quantum Satellite Communications Beyond Eagle-1

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.laiqa-horizon.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, bringing innovations 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.