Integrated Ring-based Quantum Key Distribution with Weak Measurement Enhanced Fiber-Optic Sensing Disturbance Magnitude and Location

TL;DR

This work tackles the challenge of maintaining secure quantum communication in fiber networks while continuously monitoring channel disturbances. It introduces SLIS, a Sagnac-loop architecture that fuses a phase-encoded BB84 QKD module with weak-measurement (WM) enhanced sensing and a null-frequency localization (NFL) module to locate disturbances. Experimentally, SLIS runs a 30 km loop at 22.4 kbps raw rate with QBER below 5% for extended operation, while dynamic disturbances are detected down to 100 Hz and quasi-static perturbations achieve attosecond-level time-delay sensitivity and meter-scale localization. The integrated, self-diagnosing platform supports concurrent communication and perception, offering robust, scalable quantum networks with real-time channel awareness and security enhancements.

Abstract

The deep integration of quantum communication and fiber-optic sensing is pivotal for the development of next-generation multifunctional and highly reliable secure information infrastructure. Here, we present a Sagnac-loop integrated system (SLIS) that, for the first time, combines ring-based quantum key distribution (QKD) with fiber-based weak measurement (WM) enhanced sensing and disturbance localization capabilities. In the event of communication interruption due to external disturbances, the SLIS seamlessly switches to perception system, employing interference measurement and WM techniques to monitor channel disturbances. By integrating null-frequencies localization (NFL) mode, the system precisely determines the disturbance location, enabling rapid identification of security vulnerabilities along the link. Experimental results demonstrate that, over a 30 km Sagnac loop channel, the SLIS achieves a raw key generation rate of 22.4 kbps with stable operation and clear scalability toward network expansion. In terms of perception performance, the SLIS exhibits strong capability for both dynamic and quasi-static disturbances. For dynamic perturbations, the system detects transient impacts and PZT-driven frequency variations down to 100 Hz, and enables long-distance localization via NFL alignment, with improved localization performance as the disturbance position moves farther away along the loop. For quasi-static disturbances, gravitational changes as small as 100 g are resolved, corresponding to a time-delay variation of 9.81 as. This work provides a novel technical pathway toward self-diagnosing, robust quantum networks through integrated communication and sensing functionalities.

Figures (7)

• Figure 1: Schematic diagram of the working process of the SLIS.
• Figure 2: Schematic illustration of the evolution of the optical field within the SLIS.
• Figure 3: Schematic of the relationship between the communication and sensing carriers in the SLIS.
• Figure 4: Schematic diagram of the SLIS. (a) Application methods for three types of disturbances: I. PZT-induced vibrations, II. transient impacts, and III. quasi-static pressure. (b) Post-selection setup for simulating channel time delay variations in WM sensing.
• Figure 5: Experimental results of QKD performance in the SLIS.