Xudong Wang

Spontaneous emission was long considered fickle: a quantum dot emits a photon, obeying only probability. The Purcell effect allowed amplifying it by placing the emitter in a resonator, but that only changed the rate, not the spectral shape.

Earth's magnetic field, the one that swings a compass needle, is strong. The new sensor picks up fields a hundred thousand times weaker, and it needs neither liquid helium nor bulky setups. Everything fits on a circuit board, just like the one inside your smartphone.