Guan-Jie Fan-Yuan

Determining the position of an entity can enable security-critical functionalities, such as position-based authorization for transactions and secure tracking of a high-value target. Classical means, however, have been proven incapable of providing secure position verification in the untrusted-prover case, meaning that a prover can mislead verifiers about its actual position. In this work, we propose and experimentally realize a secure position-verification protocol that leverages quantum optics and relativity within an information-theoretic framework. Using phase-randomized weak coherent states, two verifiers separated by 2 km securely verify the prover’s position with an accuracy better than 75 meters. These results establish secure position-based authentication as a practical possibility, paving the way for applications in financial transactions, disaster response, and authenticated secure communications.