Deployment and scalability of the Networked Quantum Magnetometer Array (NQMA) for subterranean detection and perimeter security applications

Developed by FieldLine Industries under sponsorship from the Department of Defense, the Networked Magnetometer Array (NQMA) is a distributed array of rubidium-based scalar quantum magnetometers designed to detect weak magnetic signals generated by tunneling activity, vehicles, and concealed objects. A 64-sensor array was deployed at the Edgar Experimental Mine in Colorado, where it has operated continuously for over a year under harsh environmental conditions. The system demonstrated exceptional resilience and achieved sub-picotesla sensitivity, enabling the localization of unmagnetized ferrous objects, such as a screwdriver, to within one meter, even under 15–20 meters of overburden. Key innovations include the Phantom Field Network (PFN) for in-situ calibration and remote testing, scalable data synchronization and uplink via 5G, and real-time localization algorithms incorporating lead field modeling. As part of a large-scale performance evaluation, the PFN was used to conduct approximately 100,000 individual experiments to quantify system performance, particularly localization accuracy as a function of dipole strength and distance from the sensor array. Under certain source conditions, localization precision reached a variation of less than 10 centimeters, for sources 12 m underground. We also demonstrated underground localization for a large source (mining vehicle) at a range of about 150 m. Results from automated and manual detection show robust system performance across various testing scenarios. These results establish the NQMA as a versatile platform for subterranean detection, perimeter security, geomagnetic monitoring, and potential use in port security and checkpoint scanning. This work advances the state of quantum sensing and offers a promising path toward real-world operational deployment in defense and commercial applications.