The cat sits in one box, but its fate is tied by an invisible thread to another box, where a radioactive atom lies. As long as no one looks, the cat is neither alive nor dead. That is Schrödinger's famous thought, and it has been nagging physicists for nearly a century. In a new paper, the cat ends up in two boxes at once, and the authors track exactly when the sentence is carried out.

The central question: at what moment does quantum uncertainty give way to a definite outcome? People usually say that measurement "collapses" the wave function, but those are just words. The authors propose a mechanism. They describe measurement as signal amplification, much like a quiet whisper turning into a loud shout through a megaphone. The amplitude of the field carrying information about the state grows over time, and at large amplification two branches appear, corresponding to different outcomes.

The most interesting part happens at the moment when the coupling to the meter is broken. It is then, and not earlier, that it is determined whether the cat is alive or dead. This agrees with macroscopic realism: large objects have definite properties even before we look at them. But there is a nuance. If, after measurement, we select the cases where the outcome is known, the amplitude distribution turns out to be narrower than the uncertainty principle allows. So the amplitudes are hidden from us, yet real.

The cat in two boxes is now not just a paradox but a model that can be tested in the lab. Optical Schrödinger cats are already being created with hundreds of photons, and parametric amplification is a standard tool. If the predictions are confirmed, the debate over the completeness of quantum mechanics will take a new turn. Perhaps hidden variables will come back into play, and the cat will finally acquire definiteness.