Multi-nodes quantum network in metropolitan area of Naples

Quantum Key Distribution (QKD) has been proven to be an unconditionally secure method for exchanging cryptographic keys under real-world conditions. By exploiting the principles of quantum physics, QKD enables the establishment of secret keys between two communicating parties, ensuring the security of transmitted data. Recently, numerous companies and research institutions have demonstrated the successful implementation of large-scale, high-speed communication systems in both laboratory settings and field tests. Additionally, several advanced network structures have been developed to facilitate secure communication via QKD, contributing to the creation of metropolitan-scale secure networks. In this work, we leverage the state-of-the-art of superconducting nanostrip single-photon detectors (SNSPDs) to enhance the performance of commercial QKD systems. These systems are deployed in a three-node network around the city of Naples, connecting an industrial hub with the Physics Department and the CNR-INO research center.The goal is to establish secure communication channels for exchanging and managing encrypted data. This work represents a significant step toward the practical realization of metropolitan-scale QKD networks and their integration into existing communication infrastructure. By using SNSPDs, we ensure high efficiency and low noise levels, contributing to more reliable and secure key distribution over metropolitan distances. The integration of these technologies demonstrates the feasibility of QKD as a cornerstone for future secure communications in urban environments.