Massimiliano Dispenza

Quantum key distribution (QKD) is an innovative technology allowing information-theoretically-secure key sharing among distant users relying only on fundamental rules of quantum physics, without assumptions about the computational power of the attacker. This work presents the architecture of the Rome QKD Metropolitan Area Network (QMAN), the different layers required to sustain such network, including the Key Management System developed by Leonardo and the interconnection with the Italian Quantum Backbone to intregrate this network in the EuroQCI program. The Rome QMAN is a quantum-safe hybrid network, made up of several nodes that are connected with both commercial fibre and a free-space link.

Twin-Field Quantum Key Distribution (TF-QKD) is an innovative family of protocols characterized by a weaker dependence of the achievable secret key rate on the channel loss, with respect to conventional QKD solutions. In this work, we discuss several important aspects encountered in TF-QKD when transitioning from point-to-point links to a network configuration. 1) The effects of path length mismatch between the two arms of the link (A-C and B-C) is discussed in several configurations. 2) The noise contributions (stronger in in-field deployment) are meticulously analyzed, their effect on the final key rate is estimated and solutions to mitigate the problem are implemented. 3) The topic of building complex and large networks with TF-QKD is tackled to find advantageous configurations. Interconnected macro-star networks based on TF-QKD are simulated by means of the “qkdnetsim” package of the network simulator “ns3”. The upcoming deployment of national QKD networks requires dedicated studies in this direction to build efficient and long-range solutions, compatible with current telecom standards.