Stopping and Freezing a Bullet

Well, not so much a bullet as pretty much any paramagnetic atom (which means most atoms). Reminiscent of Sisyphus cooling only with really big magnetic pulses instead of polarization gradients.

The principle is similar to coilguns being developed by the military to launch projectiles, only “in reverse,” Raizen says. To those atoms with their dipoles aligned opposite the beam’s direction, the pulses are like hills they have to climb, except that each hill disappears before the atoms have a chance to slide “downhill.”