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Schrödinger’s Cat is …

Roger Highfield has a post at the Telegraph site about a set of upcoming experiments that will allow us to see whether Schrödinger’s cat is alive or dead.

Schrödinger’s cat is a paradoxical thought experiment devised by Austrian physicist Erwin Schrödinger. A cat, along with a flask containing a poison and a radioactive source, is placed in a sealed box shielded against environmentally induced quantum decoherence. If an internal Geiger counter detects radiation, the flask is shattered, releasing the poison that kills the cat. The Copenhagen interpretation of quantum mechanics implies that after a while, the cat is simultaneously alive and dead. Yet, when we look in the box, we see the cat either alive or dead, not both alive and dead.

According to the many-worlds interpretation, every event is a branch point. The cat is both alive and dead—regardless of whether the box is opened—but the “alive” and “dead” cats are in different branches of the universe that are equally real but cannot interact with each other.

Another model is known as the Ghirardi–Rimini–Weber-and-Pearle theory or GRWP. In this theory, wave function collapse is a consequence of the vast numbers of atoms in a measuring apparatus interacting with whatever is being observed. Now, there is finally a prospect of lifting this debate beyond dry philosophy by actually testing the GRWP proposal using ultra-precise instruments known as matter wave interferometers to spot tell-tale signs that can reveal if one of the versions of quantum theory is correct and test how real the wave-function collapse is.

If his experiment challenges (or refutes) GWRP, it would be the simplest outcome and back the “shut up and calculate” pragmatists. But if it suggests that GRWP is correct, it could provide the first real evidence that the universe does not split into parallel worlds: that the possibilities of a living and a dead cat do indeed collapse into one reality when we look at it.
Any such experimentally verified deviation from traditional quantum predictions would mark a revolutionary turning point in physics – spurring the debate over what the wave function really means and cracking open a door to reveal a deeper level of reality. Let’s just hope ours is one of the universes in which the experiment works.

You probably should/should not read the whole thing.