Chinese Submarine-Hunting Quantum Sensor Tracks Subway Train Beneath Street

Pencil-sized device, subway-scale signal

The device was developed by Peng Xinhua and colleagues at the University of Science and Technology of China, according to a study published on September 14 in Acta Physica Sinica.

It is scarcely larger than a pencil and draws only 5 watts of power, yet it was able to detect the magnetic disturbance linked to a moving train.

The test recorded a subway train rumbling under a city street, including the train braking into a station.

The researchers’ device also clearly recorded the train’s stop and its departure under traction.

Why the test stands out

The magnetometer was built for hunting submarines, but the reported demonstration used a subway train as the tracked target in a real-world urban setting.

Its significance lies in the contrast between the device’s small size and low power use, and its ability to isolate a train’s magnetic disturbance inside the Earth’s vast background field.

The study describes that signal isolation as clear enough to follow separate stages of the train’s movement beneath the street.

Source: South China Morning Post