Schrödinger’s kittens have never been very cute, and the latest litter is no exception. Images of nebulous clouds of ultracold atoms or microscopic strips of silicon are unlikely to go viral on the internet. All the same, these exotic objects are worth heeding, because they show with unprecedented clarity that quantum mechanics is not just the physics of the extremely small.
“Schrödinger’s kittens,” loosely speaking, are objects pitched midway in size between the atomic scale, which quantum mechanics was originally developed to describe, and the cat that Erwin Schrödinger famously invoked to highlight the apparent absurdity of what that theory appeared to imply. These systems are “mesoscopic”—perhaps around the size of viruses or bacteria, composed of many thousands or even billions of atoms, and thus much larger than the typical scales at which counterintuitive quantum-mechanical properties usually appear. They are designed to probe the question: How big can you get while still preserving those quantum properties?