Eugen Dizer

A polar molecule is like a tiny dumbbell with opposite charges at its ends. Normally, such particles quickly stick together or fly apart when they meet — electric forces are too strong. But the authors of the work found a way to turn this aggressiveness into a controlled game.

In an ultracold cloud of 180,000 lithium atoms, about a thousand cesium atoms drift. They are 22 times heavier than their neighbors, which makes them nearly motionless among the fast-moving particles. When such a heavy atom absorbs light, it starts oscillating between two states, and the rate of these oscillations is called the Rabi frequency.