mfb wrote:SU3SU2U1 wrote:It can't- no one knows how to get a Born rule out of the theory. WIthout getting the Born rule, you either can't make predictions or you make wrong predictions.

The same is true for all interpretations. The square of the amplitude is just put in. Well... there actually IS an idea how it could be the result of deeper theory.

Looks like that just hides the extra premises under some jibber-jabber (as Mr T would say) about anthropics. It's still putting in rules by hand.

if you measure something symmetrical with amplitudes 1/sqrt(2), you know that you should assign both measurements probability 1/2 because you don't have any evidence that could point one way or the other. Then if you postulate the existence of many independent such qubits, you know that the amplitudes multiply and the probabilities multiply, so you can show that for all amplitudes that are a binary fraction, the Born rule holds. I'm not sure how to do the same thing for non binary-fractions though. This argument does sneak in some extra information, but only a little, and possibly the minimum.