2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/90066We analyse security costs in one segment of nested purification protocol in a large quantum cryptography network, employing the quantum switchers and repeaters. We demonstrate that exponential or even super-exponential grow of entanglement resources occurs in dependence on number of the network switchers. For this reason, an optimization in the nested strategy is suggested, preventing a stronger than the exponential grow of entanglement resources.4 pages and 3 figuresQuantum PhysicsOptimization of security costs in nested purification protocoltext