Handheld quantum sensor tracks subway train beneath city street

Chinese researchers have tested a handheld quantum magnetometer designed to detect submarines by using it to track a subway train beneath a city street, according to the South China Morning Post. The device was developed by Peng Xinhua and colleagues at the University of Science and Technology of China. In the reported demonstration, it isolated the magnetic disturbance produced by a moving train underground, showing that the instrument could detect activity below the surface in an urban setting.

The magnetometer is described as being scarcely larger than a pencil and consuming five watts of power. Its intended application is hunting submarines, but the subway test provided a practical demonstration of its ability to identify a moving source of magnetic interference. The work is described in a study published on September 14 in Acta Physica Sinica.

The supplied material does not specify the train’s depth, the distance from which it was detected, the test location or the precise performance limits of the instrument. It also does not say whether the device has been deployed for submarine detection or is still at the research and testing stage. The report identifies the subway demonstration as a striking real-world test of the compact sensor’s capabilities.