Entanglement verification protocols for distributed systems based on the Quantum Recursive Network Architecture

In distributed systems based on the Quantum Recursive Network Architecture, quantum channels and quantum memories are used to establish entangled quantum states between node pairs. Such systems are robust against attackers that interact with the quantum channels. Conversely, weaknesses emerge when an attacker takes full control of a node and alters the configuration of the local quantum memory, either to make a denial-of-service attack or to reprogram the node. In such a scenario, entanglement verification over quantum memories is a means for detecting the intruder. Usually, entanglement verification approaches focus either on untrusted sources of entangled qubits (photons, in most cases) or on eavesdroppers that interfere with the quantum channel while entangled qubits are transmitted. Instead, in this work we assume that the source of entanglement is trusted, but parties may be dishonest. Looking for efficient entanglement verification protocols that only require classical channels and local quantum operations to work, we thoroughly analyze the one proposed by Nagy and Akl, that we denote as NA2010 for simplicity, and we define and analyze two entanglement verification protocols based on teleportation (denoted as AC1 and AC2), characterized by increasing efficiency in terms of intrusion detection probability versus sacrificed quantum resources.