How a Beam of Light Turns into Schrödinger's Cat ⚡ экспресс

A laser beam inside a special crystal spontaneously turns into a “Schrödinger’s cat”—a mixture of two states. Erwin Schrödinger dreamed up this paradox for an atom, but now physicists see it happen with an entire stream of photons.

Light is like a company of soldiers on a parade ground. As long as nothing disturbs them, all the photons march in lockstep—that’s coherence, and their motion is capped at light’s ultimate speed limit. But a crystal that doubles the frequency (turning red into blue) makes the vacuum tremble. The vacuum spawns virtual particles that wink in and out, tugging at the photons. The rhythm falters, and the formation splits into two squads marching out of sync.

Even for beams with 10 million photons, this disorder doesn’t destroy the quantum superposition. The calculations used a hybrid method: quantum mechanics for small numbers and a model of trajectories for intense streams. The outcome was checked with negative peaks on a mathematical state map—something impossible in the classical world. Roy Glauber described coherence, Serge Haroche grew “cats” in resonators, but the crystal turned out to be far simpler. And from sheer emptiness you can squeeze out real light if you rapidly compress space—the dynamic Casimir effect.