How decoherence destroys superpositions

[Simon Phoenix]

I have and hold to the ignorance ensemble interpretation which basically answers - why do we get any outcomes at all - by somehow.

and that's how 'textbook' QM answers it too - we get something, somehow. I guess I see decoherence, as applied to measurement theory, as an attempt to resolve the unitary dynamics, non-unitary measurement issue of QM. I've not really seen any interpretation of QM that I'm personally 100% happy with, they all seem to me to have this character of sweeping something under a rug - they just use different rugs.

Perhaps the standard QM advice should be re-written - "just shut up and sweep"

 

[vanhees71]

That's the best advice you can indeed give in QM 1, but with the hint that observables and states are not abstract operators in Hilbert space but clearly defined descriptions of measurement devices and preparation prescriptions, and these are defined by the experimentalists in the lab or the observers at their telescopes or however you observe the world around us. The only thing you need to describe observations with the formalism is just Born's rule, and you should take it seriously: If an observable is indetermined, it's indetermined, and there are only probabilities known (provided the state is known with sufficient precision). If you measure it you get, by construction of the real-world measurement apparatus by a good experimental physicist or engineer, a well-defined value, and if you repeat the experiment sufficiently often with sufficiently well prepared ensembles you can measure the probability and compare with the prediction from the formalism. The most amazing thing about QT is, how accurate it makes these predictions and how robustly is withstood all attempts to disprove it.