Julian Schmitt

A pot of water always boils the same way: hit 100 degrees and bubbles start. Quantum fluids are different. When a cloud of atoms is cooled to near absolute zero, it can turn into a single matter wave — a Bose–Einstein condensate. But the transition itself, it turns out, can happen in three different ways.

Two connected vessels joined by a tube usually settle at the same water level. Here, the vessels start rocking on their own because each has a leak, and the leaks are different. Light in two dimples of a micromirror behaves the same way: photons flow from one well to the other, but they are lost at different rates. These losses do not damp the motion; they set its rhythm.