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But also BM and any other interpretation of QT has a measurement problem, if you think there is one. If I understand the philosophers right, their problem is that they think it's not understood, which outcome a measurement on a single quantum system will have, knowing the state (even if it's complete knowledge, i.e., if the system is prepared in a known pure state).lukephysics said:
They exspect that the dynamics of the theory explains, why this state through interaction with a measurement apparatus "collapses" to the eigenstate of the operator that represents the measured observable. That's however in contradiction to the standard version of QT, because unitary time evolution does not lead to such a dynamics. Rather you still have a superposition of entangled states of the measured system and the pointer states of the measurement device. There are two ways out:
(a) One accepts that Nature is inherently random and that the outcome of measurements are thus irreducibly probabilistic. All QT delivers are the probabilities for the outcomes of measurements, and there is nothing more in Nature. That's the minimal statistical interpretation. There's no collapse, the quantum state is purely epistemic. For me that's the most plausible solution of the measurement problem, which is only apparent. It's just a problem for our worldview, which is due to everyday experience with macroscopic systems, whose relevant macroscopic observables behave according to classical physics with determinism as an emergent, approximate phenomenon. All observations and high-precision tests of QT in very many manifestations are consistent with this assumption.
(b) Nevertheless, that's indeed only an educated belief, founded on the overwhelming success and lack of failure of (minimally interpreted) QT. It cannot be ruled out, of course, that maybe QT is nevertheless incomplete, and then QT has to be modified, maybe in such a way that there's an inherent collapse mechanism in the dynamics. What's for sure ruled out is naive EPR "Local Realism". This is the great achievement of Bell's theoretical and Clauser's, Aspect's, et al's experimental work.
What's an RNG? Also one has to accept how Nature is found to behave. Whether there's a god who created the universe the way it looks, is not a question that can decided by the pure sciences. That's a matter of private belief for any individual.lukephysics said:
For me CI is inconsistent. Even the versions, which do not assume a collapse (e.g., Bohr's as well as Heisenberg's version, as far as I can guess from their enigmatic philosophical writings), there's still the "quantum-classical cut", which in no way could be hitherto observed. To the contrary with more and more refined metrology bigger and bigger systems can be shown to behave according to QT (e.g., the motions of the LIGO mirrors, sevel 10kg objects, behave quantum theoretical and show "zero-point motion" of quantum oscillators).
I'm not sure about MWI. On the one hand they claim that there's nothing than unitary time evolution and the "wave function of the universe" is all there is. On the other hand, for the application of QT, again I have to assume Born's rule for subsystems as in standard QT. I don't know, what's gained with MWI compared to the minimal interpretation.
I guess with PW you mean "pilot wave", i.e., de Broglie-Bohm. Within non-relativistic theory it's a consistent mathematical addition to standard QT, but it's not solving any "measurement problems" either. Particles do not follow Bohmian trajectories but behave probabilistically as predicted by standard QT. All attempts to extend the Bohmian program to relativstic QT I'm aware of are even less convincing, violating in the one or the other way Poincare covariance, i.e., they are not relativstic at the end.lukephysics said: