Secure Positioning System Verified over 2km Using the Laws of Physics

Scientists have long sought methods for secure position verification, as classical approaches lack inherent security against deceitful provers. Guan-Jie Fan-Yuan, Yang-Guang Shan, and Cong Zhang, alongside Yu-Long Wang et al. from the University of Science and Technology of China and Guangdong University of Technology, now demonstrate an experimentally realised protocol utilising optics and relativity to address this challenge. Their research establishes secure position-based authentication by verifying a prover’s location with sub-75 metre accuracy across a 2km distance, employing phase-randomised weak coherent states. This advancement represents a significant step towards practical applications in areas demanding trustworthy location data, including financial security, disaster relief coordination, and authenticated secure communications. Quantum verification of location using coherent states over extended distances remains a significant challenge in quantum communication Scientists have demonstrated a secure position-verification protocol leveraging quantum optics and relativity, achieving a verification precision better than 75 meters over a 2km distance. This breakthrough addresses a fundamental security vulnerability in classical positioning systems, where a prover can falsely claim a location without detection. The research establishes secure position-based authentication as a practical possibility, with potential applications spanning financial transactions, disaster response, and secure communications. Central to this achievement is the use of phase-randomized weak coherent states, which allow two verifiers to securely confirm the prover’s location within the specified accuracy. This work overcomes limitations inherent in previous quantum position-verification attempts by eliminating the need for single-photon sources and addressing substantial computational demands.

The team developed a system utilizing readily available coherent-state sources, insensitive to modulation loss and compatible with high repetition rates, enabling a high-speed, low-loss polarization-encoding scheme. A Sagnac architecture, constructed from a micro-assembled rotated circulating splitter, achieves high-fidelity polarization-state preparation, while a high-frequency optical switch and superconducting detectors facilitate low-loss polarization analysis, resulting in an overall quantum-optical efficiency of 70% with an error rate of 0.27%. To mitigate latency issues associated with transmitting classical messages, dedicated classical links were engineered using dense-wavelength-division-multiplexed on, off keying, anti-resonant hollow-core fiber transmission, and high-speed PIN photodiode detection. This minimal parallel transmission design, combined with a near-light-speed channel, allows for scalable message sizes with negligible excess latency. Furthermore, a hardware lookup table implemented on a field-programmable gate array and double data rate memory array enables fast credential computation with a latency below 118ns, even within a vast computation space exceeding 10330985980541, corresponding to a security parameter of n = 40. The protocol functions by requiring the prover to perform operations based on information from the verifiers and return the results for verification, with the round-trip time of information exchange bounding the prover’s position. This system represents a complete quantum position verification, combining quantum optics with relativity within an information-theoretic framework, and indicating practical relevance for secure authentication in various real-world scenarios. Experimental setup and protocol for 2km quantum position verification are detailed in the following sections A 72-qubit superconducting processor forms the foundation of this secure position-verification protocol, leveraging optics and relativity within an information-theoretic framework. Two verifiers, separated by a 2km distance, securely verify the prover’s position with an accuracy exceeding 75 meters using phase-randomized weak coherent states. The research establishes finite-size secure bounds and introduces a parameter-optimization method to enhance robustness, elevating quantum position verification to a practical level. The experimental system comprises three main units: V1 and V2, the verifiers, and P, the prover. V1 and V2 each contain a classical bits preparation unit, a quantum state preparation unit for message preparation, and a credential receive unit for position inference. P incorporates a Boolean function unit and a quantum state measurement unit for credential generation. The use of coherent states mitigates the impact of quantum state preparation loss, a critical factor in successful protocol execution. To minimize signal degradation, ultra-low-loss fiber with an attenuation of 0.142 dB/km is employed for the channel. Optical switches with 0.6 dB insertion loss facilitate basis selection, while superconducting single-photon detectors with 90% efficiency perform detection, achieving an overall system transmission efficiency of 70%. A newly developed fast-response high-voltage driver enables these switches to operate at 2MHz, increasing the security resource threshold to 2(n/4 −5) Mbps. Quantum states are prepared using a Sagnac-based setup generating four polarization states, achieving a quantum bit error rate below 0.27% through a rotated circulating splitter. Latency is minimized through a combination of hardware and techniques. A circuit based on FPGA and DDR memory implements Boolean functions, utilizing 1 Tb of DDR capacity corresponding to n = 40, with a delay of 117.3ns primarily due to DDR access. Transmission delays are reduced by employing 978.4m and 981.2m AR-HCF links between verifiers and the prover, alongside DWDM-OOK encoding for simultaneous bit transmission, resulting in excess delays of 22.05ns and 22.39ns respectively. A GaN-based high-voltage driver enables 400V peak-to-peak voltage switching within 50ns, and single-photon detector internal wiring contributes a 17.7ns delay. Secure two-kilometre quantum position verification exceeds 75-metre accuracy thresholds Two verifiers, separated by 2 kilometers, securely verified a prover’s position with an accuracy exceeding 75 meters. This achievement establishes secure position-based authentication as a practical possibility for applications including financial transactions and disaster response. The research demonstrates a complete quantum position verification system combining quantum optics and relativity within an information-theoretic framework. Phase-randomized weak coherent states were utilized, resolving multiphoton security issues and eliminating the need for single-photon sources. Quantum-optical efficiency reached 70 percent, while maintaining an error rate of 0.27 percent during operation. A high-speed, low-loss polarization-encoding scheme was implemented using a Sagnac architecture constructed from a micro-assembled rotated circulating splitter to achieve high-fidelity polarization-state preparation. Dedicated classical links, based on dense-wavelength-division-multiplexed on, off keying signal generation and anti-resonant hollow-core fiber transmission, were developed to address latency issues. These links, combined with high-speed PIN photodiode detection, enabled scalable data transmission with negligible excess latency. Hardware lookup tables, built on a field-programmable gate array and double data rate memory array, facilitated large-n high-speed credential computation. Computation latency remained below 118 nanoseconds over a computation space exceeding 10330985980541, corresponding to a parameter value of n = 40. This level of computation supports 22n doubly-exponential credential computations, approximately 10315653 for n greater than 20, ensuring robust security. The study’s building-scale verification precision, better than 75 meters, indicates practical relevance for secure-zone dimensions and similar applications. Secure remote authentication via relativistic signalling and quantum optics offers unparalleled security guarantees Researchers have demonstrated a secure position-verification protocol utilising optics and relativity, establishing secure position-based authentication as a practical possibility. Two verifiers, separated by a distance of 2km, were able to securely verify the position of a remote prover with an accuracy exceeding 75 meters. This achievement relies on an information-theoretic framework incorporating phase-randomized weak coherent states and leverages the fundamental limits imposed by the speed of light and the distinction between classical and quantum resources. The system achieved a verification range of 74.3 meters with a response delay of 247.8 nanoseconds, indicating a level of practical significance for real-world applications. Adversaries attempting to compromise the system would require distributing an infeasibly large number of entangled qubit pairs, over 10 million per second with perfect fidelity, exceeding current technological capabilities by a substantial margin. This work elevates quantum position verification from a theoretical concept to a deployable technology, offering solutions for position-based authentication in scenarios such as secure financial transactions, disaster response coordination, and access control. The authors acknowledge that the current implementation is limited by the 2km separation between verifiers and the Boolean size of n=40 used in the protocol. Future research may focus on extending the verification range and exploring the scalability of the system for larger networks. Potential applications include tracking critical assets during disaster relief, securing high-value goods, and controlling access to sensitive locations or resources, providing a new layer of security for geographically-dependent operations. 👉 More information 🗞 Relativistic Position Verification with Coherent States 🧠 ArXiv: https://arxiv.org/abs/2602.01787 Tags: