Technological advances with real impact

The project has achieved innovations throughout the entire quantum communications cycle, from physical devices to network management. Particularly noteworthy is the integration of quantum key distribution (QKD) systems, a technology that protects communications even against future quantum or disruptive technologies. QKD systems from all manufacturers have been integrated into the European ecosystem. Significant progress has also been made in satellite quantum links within the Q ANSER mission, including space-qualified polarisation tracking systems and complex network control tools.

In this regard, researchers from IMDEA Networks and UC3M developed an advanced testbed solution for secure end-to-end key distribution, combining QKD with cloud-native and SDN architectures, which was also hosted in NEXTONIC’s data centre. This resource is based on a virtualised and disaggregated key management layer deployed on Kubernetes clusters, enabling dynamic session establishment in complex scenarios involving multiple trusted-node hops. The solution has been evaluated by means of Quditto, which is a digital twin service for quantum communications networks for research and experimentation, also developed within the framework of the project. The tests have demonstrated key distribution, robustness against attacks and adverse conditions, and continuous, scalable and secure system operation, with real-time fault detection and QoS. This work was carried out by IMDEA Networks’ NETCOM Lab group in collaboration with the Department of Telematic Engineering at UC3Madrid and the NEXTONIC laboratory. In addition, active collaboration is ongoing with groups from the universities of Vigo and the Basque Country to assess deployments in their regional networks.

IMDEA Networks has also contributed in two additional lines of work in quantum technologies: security and quantum algorithms. The security work, carried out by the IAG and Cybersecurity groups, reviewed the state of the art in quantum network security, including threat models, attack types and proposed mitigations, with the aim of identifying future challenges linked to the integration of quantum and traditional networks, flawed assumptions, oversimplified models and interconnection issues between operators; the study will be published in the coming months.

In parallel, the Opportunistic Architectures group has worked on quantum consensus, designing and testing scalable quantum circuits on IBM hardware to bring quantum network components into a shared symmetric state, and on quantum annealing for Quadratic Knapsack problems, with new formulations consistently outperforming existing ones.

At the same time, the project has promoted advances in quantum information processing, with applications in computing, sensing and future distributed networks. For example, the Spanish Centre of Metrology has developed a quantum optical frequency standard with the potential to distribute ultra-precise and more secure timing signals through fibre-optic networks. In addition, algorithms and artificial intelligence-based techniques have been implemented to optimise quantum systems, with milestones such as the estimation of gravitational wave parameters through quantum computing and the enhancement of circuits on real hardware.

Through these achievements, MADQuantum-CM leaves behind an operational infrastructure, advanced technological capabilities and a collaborative network integrating research, industry and institutions. Madrid is therefore taking a decisive step towards secure communications and the future quantum internet in Spain and Europe.