Scalable Quantum Networks Enabled by Quditto’s Open-Access Emulation Platform

Quantum Key Distribution promises unhackable communication, but practical deployment faces significant hurdles due to the expense and complexity of building dedicated quantum networks. Blanca Lopez, Angela Diaz-Bricio, and Javier Perez, from the IMDEA Networks Institute, alongside colleagues at Universidad Carlos III de Madrid, address this challenge with Quditto, a new platform that emulates realistic quantum networks. Quditto combines accurate modelling of quantum channels with a simple, standardised interface, allowing researchers to test and refine quantum communication protocols without the need for costly hardware or fibre infrastructure. This innovative approach supports complex network configurations and detailed channel modelling, ultimately accelerating the development and validation of secure quantum communication systems and paving the way for wider adoption of this transformative technology.

Emulating Quantum Networks with High Fidelity

This work introduces Quditto, a novel platform for emulating quantum networks, providing a comprehensive and flexible environment for researchers and developers to design, test, and validate quantum communication systems. Quditto focuses on accurately modeling quantum channels, crucial for realistic simulations, and supports the creation of complex network topologies with various quantum devices. The platform’s modular design enables easy integration of different quantum protocols, devices, and management features, and it implements the ETSI standard for key delivery, facilitating real-time communication and interoperability. Through validation experiments, the team gathered data on platform performance, demonstrated the ability to integrate and test different quantum key distribution protocols, and tested the system with various channel models, including those with eavesdroppers and non-ideal conditions.

These experiments demonstrate the significant impact of channel quality on system performance, with better channels leading to faster key generation and higher key rates. Quditto provides a valuable tool for designing, testing, and validating quantum communication systems before deployment, and its modularity and support for industry standards make it a promising solution for advancing the field of quantum communication. Recognizing the challenges posed by costly hardware and signal degradation in fiber optics, the team developed a system that coordinates the automatic deployment of a realistic network across existing classical equipment and cloud infrastructures. This approach bypasses the need for dedicated, low-loss channels and expensive quantum hardware, enabling distributed experimentation without physical infrastructure constraints. The core of Quditto lies in its modular architecture, which integrates high-fidelity quantum-channel modeling with a standardized Application Programming Interface compliant with ETSI GS QKD 014.

Researchers harnessed the NetSquid quantum simulator to provide realistic quantum behavior within the emulated network. This integration allows users to interact with the network nodes in real time, mirroring the experience of working with physical quantum key distribution hardware. The system delivers the ability to create networks of arbitrary topology, abstracting away the underlying hardware and execution environment. Scientists implemented an automated deployment process, significantly improving the precision of quantum-behavior modeling. Quditto’s design supports pluggable protocol implementations, complex key management schemes, and detailed channel models, including variable attenuation and decoherence, allowing for comprehensive testing under realistic conditions. Validation involved deploying networks of various sizes and demonstrating the platform’s flexibility through proof-of-concept scenarios featuring eavesdropper attacks and heterogeneous channel conditions. This work delivers a complete, standards-compliant emulation framework capable of modeling high-fidelity quantum behavior, supporting multi-device topologies, and maintaining compatibility with commercial quantum key distribution hardware APIs. The system functions as a complete emulator, allowing classical computing equipment to behave in real time as quantum communication hardware would, bridging the gap between simulation and real-world deployment. Quditto’s architecture comprises three key components: the Quditto orchestrator, the modeling engine, and the Quditto nodes.

The nodes handle application requests for cryptographic material via a standardized API, forwarding each request to the modeling engine using a Pub/Sub protocol. When a client requests a key, a “modeling request” message is published, specifying the neighbor involved and the amount of cryptographic material needed. The modeling engine then executes the quantum key distribution protocol, generating the key and calculating the time required for physical equipment to create it. Crucially, the system waits the calculated time before publishing a “result” message, accurately reproducing real-hardware timing.

Experiments demonstrate Quditto’s ability to faithfully reproduce the operational behavior of quantum key distribution infrastructure. The platform accurately models key exchange timing; when a client requests a key, the system waits the calculated time before delivering the cryptographic material, mirroring the behavior of physical equipment. This precise timing is achieved through the modeling engine’s execution of the quantum key distribution protocol and subsequent delay before publishing the “result” message. The system supports real-time interactive and distributed deployments, enabling researchers to evaluate a broad range of experiments under realistic and reproducible conditions. By combining high-fidelity quantum channel modelling with a standardized key-delivery Application Programming Interface, Quditto allows researchers to interact with emulated networks in a manner closely mirroring real-world hardware deployments. The platform’s modular design supports complex network topologies, diverse key management schemes, and detailed channel characteristics, including variable signal loss and decoherence. Validation of Quditto involved deploying networks of varying sizes and demonstrating its capabilities through simulations of eavesdropper attacks and heterogeneous channel conditions.

The researchers highlight that existing tools often lack either the accurate quantum modelling, support for multi-device networks, or compatibility with standard hardware interfaces that Quditto provides. The authors acknowledge a reliance on SimulaQron in previous work, which Quditto overcomes with its improved modelling accuracy. Future work may explore expanding the platform’s capabilities and applying it to more complex network scenarios, ultimately facilitating the development and deployment of practical, secure quantum communication systems.