Atoms, like a swarm of fireflies, shine in unison. When they flash together, the light multiplies — a hundred atoms shine ten thousand times brighter than one. Physicists have turned this trick into a heat engine. A typical motor needs both a hot and a cold source, but here the atoms operate with just a cold one.

The cycle is simple: atoms are synchronously charged with energy, and they release it in a powerful burst. The secret is that power doesn't grow in direct proportion to the number of atoms, but much faster. If one atom produces one unit of power, two produce four, and ten produce a hundred. Because of this, efficiency approaches 100%: the inevitable energy losses, entropy, nearly vanish.

Such an engine opens the door to microscopic devices with fantastic efficiency. It builds on the discoveries of Nobel laureates David Wineland and Serge Haroche. The simplest systems, like the hydrogen atom, are studied using spectroscopy, the precise measurement of light.