5W handheld quantum magnetometer tracks subway train underground

Researchers at China's University of Science and Technology demonstrated a handheld quantum magnetometer about 7 cm³ in size that runs on 5 W and tracked a subway train moving beneath a city street. It offers roughly 10 pT/√Hz sensitivity in the 0.1–10 Hz range and a 25,200 nT/s slew rate, and also recorded a G4 geomagnetic storm and located a buried metal rod.

• Sensor is ~7 cm³, uses 5 W, sensitivity ~10 pT/√Hz
• Slew rate 25,200 nT/s vs ~10,000 nT/s for QuSpin Mz
• Recorded a G4 geomagnetic storm on June 1, matching INTERMAGNET data
• Blind survey found a rod buried 0.5 m deep in a 40×25 m area