Schrödinger's cat usually hides in thought experiments — alive and dead at the same time. This time, it was caught in the lab: a light pulse was made to be in two opposite states at once, like a coin hovering in the air, heads and tails at the same time.

To do this, they took two individual photons — particles of light that can be counted one by one, like apples in a basket. One photon was, so to speak, 'single,' the other 'double.' They mixed them on a half-silvered mirror, which randomly transmits or reflects light. When the right signal flashed at the output, the pulse was in a 'cat' state — a mixture of two opposite waves.

Why does this matter? Quantum computers make errors from the slightest noise, like an orchestra thrown off by a cough in the audience. 'Cat' states are the basis of codes that allow errors to be detected and corrected without destroying the computation. Now such 'cats' can be made large and repeated many times.

The coin suspended in midair has finally become not just a thought experiment but a working tool.