Detecting dishonest parties in a network: A quantum walk based algorithm

Inhalt:
A quantum network enables the execution of advanced protocols like distributed quantum computing, quantum metrology, quantum cryptography, and long-distance quantum communication. Malicious nodes, or dishonest parties, pose significant threats to these protocols, being notoriously difficult to detect and capable of causing severe disruption. We present a general quantum network protocol framework designed to address malicious activities by dishonest parties. Within this framework, we develop a test protocol based on quantum walks that efficiently detects such dishonest nodes. Our protocol exploits unique quantum properties—quantum interference, quantum tunneling, and quantum counterfactuality—which have no classical counterparts, thus offering substantial quantum advantages. Furthermore, we demonstrate that dishonest parties find it extremely challenging to spoof the test, as it relies on the initial state prepared by a trusted node.