The surprise at the bottom of the infinite quantum well

Who remembers the quantum particle trapped in an infinite square well? Ya’ll probably still havin nightmares about it. Turns out there is an interesting new take on this problem that has physicists all a-sea.

For any bods out there who ain’t familiar with it, the simplest problem in any course of quantum mechanics is this: what happens to a quantum particle trapped in a well of a particular width but with infinite sides. The answer is that the probability of finding the particle in any part of the well has a wavelike distribution. This is every physics undergraduate’s shocking introduction to the wave-like behaviour of quantum particles.

It’s straightforward to tackle but start tinkerin’ with this problem and yer get some interesting behaviour. Claude “Acute” Aslangul at the Laboratoire de Physique Theorique de la Matiere Condensee in Paris, asks what happens when you suddenly increase the width of the quantum well.

His answer is that the probability distribution adopts a weird and very un-wavelike pattern and that this pattern is independent of the size of the expansion.

This is a piece o’ good ol’ fashioned physics and here’s a good ol’ fashioned problem for ya: what on Earth is going on here? How can we explain this unwave-like behaviour in physical terms?

Ref: arxiv.org/abs/0709.1101: Surprises in the Suddenly-Expanded Infinite Well

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