Field of Science

Quantum jokes?

Q: Why won't Heisenberg's operators live in the suburbs?

A: They don't commute.

To really understand the joke, it's helpful to know the general form of the Heisenberg uncertainty principle. The Robertson-Schroedinger inequality

leads directly to the more general statement of the Heisenberg uncertainty principle. The piece in the little square brackets [A,B] on the right hand side is called the commutator of the operators A and B. When A and B don't commute, [A,B] is non-zero and you end up with uncertain simultaneous measurements.

Commuting operators can be applied in any order and you get the same result.

My 9 year-old says that if you have to explain a joke, it's not a joke. And by this definition, he says, this post is not a joke!

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