Optimal Quantum Key Distribution Networks in npj Quantum information

ISC researchers C. Castellano, V.Brosco and L. Pilozzi coauthored an interesting work published in npj quantum information.

Optimal quantum key distribution networks: capacitance versus security

L. Cirigliano, V.Brosco, C. Castellano, C. Conti, L. Pilozzi,  npj Quantum Information 10, 44 (2024)


The rate and security of quantum communications between users placed at arbitrary points of a quantum communication network depend on the structure of the network, on its extension and on the nature of the communication channels. In this work we propose a strategy for the optimization of trusted-relays based networks that intertwines classical network approaches and quantum information theory. Specifically, by suitably defining a quantum communication efficiency functional, we identify the optimal quantum communication connections through the network by balancing security and the quantum communication rate. The optimized network is then constructed as the network of the maximal quantum communication efficiency connections and its performance is evaluated by studying the scaling of average properties as functions of the number of nodes and of the network spatial extension.

a Distribution of N = 20 points in a square of size L representing the users of a QKD network. The colored lines represent possible paths between users a and b. b Maximum spanning tree for N = 40 nodes. Here and in the following panels the red edges represent the optimal path between user a and user b. Nodes are colored according to their degree. c–f Maximal Quantum Communication Efficiency networks , obtained using our optimization algorithm, for N = 40, L = λ0 and α = 0, 0.2, 0.3, 1.