The research team led by Academician Guo Guangcan of the University of Science and Technology of China (USTC), including researchers Han Zhengfu, Chen Wei, Yin Zhenqiang, Wang Shuang, and their collaborators, has combined the fundamental principles of quantum mechanics with relativistic spacetime constraints to achieve provably secure quantum secure positioning, which can credibly verify a target's location, providing a new technological approach for safeguarding location information security in modern information systems. The related research findings were recently published online in the international academic journal Nature Physics.
Location information is one of the fundamental elements supporting human activities. Reliably verifying a target's true location enables positioning systems not only to determine where a target is, but also to judge whether its location is authentic and trustworthy, thereby endowing location information with new functions such as identity authentication and security credentials. This can provide security guarantees for important scenarios such as commercial transactions, emergency rescue, and public safety.
However, within the classical technological framework, attackers can forge their own location by copying, forwarding classical verification information, and coordinating responses. Quantum information, on the other hand, follows quantum physical principles such as the no-cloning theorem, and combined with relativistic spacetime constraints, can achieve location verification with information-theoretic security. Nevertheless, this scheme imposes extremely stringent requirements on transmission loss, system error rates, and response delays, and had long remained experimentally unverified.
Image source: University of Science and Technology of China
The research team developed a quantum secure positioning theoretical protocol oriented toward practical experimental conditions, and on this basis achieved complete experimental verification for the first time. The team first designed a security protocol based on weak coherent states, significantly enhancing the loss tolerance of practical systems. To address the error rate issue in quantum state preparation, the team further designed a Sagnac quantum state preparation scheme based on a micro-assembled ring splitter, reducing the quantum bit error rate to 0.27%.
On the other hand, constrained by relativistic spacetime relations, system response delay directly affects the accuracy of quantum secure positioning. To this end, the team developed key technologies including multi-wavelength intensity encoding, hollow-core fiber low-latency transmission, and high-speed random logic function processing, compressing the overall system delay to the order of hundreds of nanoseconds and achieving positioning accuracy better than 75 meters, reaching the spatial scale of a single building. The experimental results verified the feasibility of quantum secure positioning under realistic conditions and demonstrated performance potential for practical applications.
The researchers stated that this achievement expands the role of location information in modern information security systems and opens up new technological directions for developing novel location-based security mechanisms and information processing methods.