The original version of this story appeared in Quanta Magazine.
Nearly a century ago, the physicist Erwin Schrödinger called attention to a quirk of the quantum world that has fascinated and vexed researchers ever since. When quantum particles such as atoms interact, they shed their individual identities in favor of a collective state that’s greater, and weirder, than the sum of its parts. This phenomenon is called entanglement.
Researchers have a firm understanding of how entanglement works in idealized systems containing just a few particles. But the real world is more complicated. In large arrays of atoms, like the ones that make up the stuff we see and touch, the laws