Derek F. Jackson Kimball

Tiny magnets inside atoms, nuclear spins, can 'freeze' for long minutes in a cold crystal. This hinders the quick tuning of quantum sensors: everything takes too long to reach the desired state. Physicists have found a way to nudge them with light.

A tiny magnetized sphere floats in a vacuum, held by invisible fields. It starts to spin around the axis of the magnetic field, just like a top that's been given a gentle nudge. That's precession. But when the sphere becomes really small, quantum laws come into play.