Secure Information Infrastructure Advances with Quantum Sensing and Disturbance Localization Capabilities

The demand for secure communication networks that also possess robust monitoring capabilities drives innovation in quantum technologies, and a team led by Weiqian Zhao, Wenzhao Huang, and Zifu Su, all from South China Normal University, now demonstrates a significant step forward. They present an integrated system that combines quantum key distribution with advanced fibre-optic sensing, creating a network capable of both secure communication and real-time disturbance detection. This novel approach allows the system to not only generate encryption keys using quantum principles, but also to immediately identify and pinpoint the location of any interference along the fibre optic link, offering a new level of security and reliability. Experimental results, achieved over a 30km fibre loop, reveal a key generation rate of 22.4 kbps alongside the ability to detect disturbances ranging from rapid impacts to minute gravitational changes, paving the way for self-diagnosing and exceptionally robust communication networks.

QKD and Fiber Sensing for Simultaneous Security

This research details a novel system integrating quantum key distribution (QKD) with fiber optic sensing for simultaneous secure communication and environmental monitoring. The system combines the security of QKD with the sensitivity of fiber optic sensors, allowing for secure data transmission and real-time monitoring of parameters like strain, temperature, or pressure, all using the same fiber infrastructure. This system achieves both secure communication and sensing simultaneously, reducing infrastructure costs and complexity, and is suitable for applications such as critical infrastructure protection, smart grids, the oil and gas industry, aerospace, and defense and security. The system leverages QKD protocols to establish a secure key between communicating parties and utilizes techniques like Fiber Bragg Gratings or Raman scattering to measure physical parameters, employing wavelength division multiplexing to separate the QKD and sensing signals. This research presents a promising approach to building secure and intelligent sensing networks by combining the strengths of quantum communication and fiber optic sensing technologies, addressing the growing need for both data security and real-time monitoring in various critical applications.

Sagnac Loop for Quantum Key and Diagnostics

Scientists engineered a Sagnac-loop integrated system (SLIS) that simultaneously achieves secure key distribution and high-fidelity channel diagnostics, representing a significant advance in quantum network development. The core of the system utilizes a 30km fiber Sagnac-loop, within which a phase-encoded BB84 quantum key distribution module operates alongside a weak measurement-based module for precise time delay estimation. Harnessing weak measurement and weak value amplification techniques, the team achieved exceptional sensitivity to subwavelength disturbances, detecting dynamic perturbations, including transient impacts and PZT-driven frequency variations, down to 100Hz. Furthermore, the study developed a null-frequencies localization (NFL) method, based on interference characteristics, to precisely estimate disturbance positions along the fiber loop.

Experimental results demonstrate that the SLIS achieves a raw key generation rate of 22.4 kbps while maintaining a quantum bit error rate below 5% during 20 minutes of continuous operation, without requiring active compensation. This innovative system offers distinct advantages in sensing precision, stability, and system-level integration, paving the way for scalable communication and sensing co-design in future robust quantum networks.

Secure Communication and Disturbance Sensing Integrated System

Scientists have developed a Sagnac-loop integrated system (SLIS) that simultaneously achieves secure key distribution and high-precision sensing of disturbances within a fiber-optic network. This breakthrough integrates ring-based quantum key distribution (QKD) with fiber-based weak measurement (WM) enhanced sensing, creating a system capable of both communication and real-time channel monitoring. In the event of a communication interruption, the SLIS seamlessly transitions to a perception system, employing interference measurement and WM techniques to identify the source of the disturbance. Experiments demonstrate that, over a 30km Sagnac loop channel, the SLIS achieves a raw key generation rate of 22.

4 kbps with stable operation. The system exhibits strong capability in detecting both dynamic and quasi-static disturbances, accurately detecting transient impacts and PZT-driven frequency variations down to 100Hz, and utilizes null-frequencies localization alignment to pinpoint the disturbance location. Furthermore, the SLIS resolves gravitational changes as small as 100g, corresponding to a time-delay variation of 9.81 as, demonstrating exceptional sensitivity to quasi-static disturbances. By combining secure communication with integrated sensing capabilities, this work delivers a novel technical pathway toward self-diagnosing, robust quantum networks and represents a significant step forward in the development of advanced information infrastructure.

Secure Communication and High-Precision Fiber Sensing

This research demonstrates a Sagnac-loop integrated system that successfully combines quantum key distribution with fiber-optic sensing capabilities, representing a significant advance in secure communication infrastructure. The system operates by seamlessly switching between secure key exchange and environmental monitoring when disturbances are detected, enhancing robustness against potential threats and ensuring communication integrity. Experimental results, achieved over a 30km fiber loop, confirm a stable key generation rate alongside the ability to detect vibrations as low as 100Hz and resolve gravitational changes with attosecond-level precision. The integrated approach allows for concurrent operation of communication and sensing functions, enabling real-time monitoring of channel conditions and potential eavesdropping attempts, while also supporting multi-user scalability. This work establishes a practical and extensible platform for integrated quantum communication and sensing, paving the way for self-diagnosing and resilient networks capable of adapting to changing environmental conditions.