Question

A quick wikipedia search will reveal the many different approaches to the measurement problem in quantum theory. What I find strange is that they even make up all these weird hypothesis like true randomness, many worlds, bohm and other interpretations when there isn't any ToE they're working it out from. I'm just a layman so maybe my assumption is wrong, but wont a fundamental theory inevitably change quantum theory?

Is really a realistic model where superpositions are nothing but lack of information on our part not likely to come from the ToE?

To my layman mind it seems premature to even begin to try to answer these questions if a theory of everything isn't in place. Or is there actually a reason that people are trying to solve this now? Such as: no matter what the ToE is, quantum theory wont change, superpositon will always exist etc.?

Answer 1

for all practical and experimentally testable purposes, the measurement theory was understood in the late mid 1920s, soon after quantum mechanics was discovered, and the "measurement problem" was solved at the level of phenomenology. The old interpretation of quantum mechanics left some questions open but from an empirical viewpoint, they were "academic questions" only.

Later progress, especially the derivations of decoherence in the 1980s, has confirmed the Copenhagen picture and derived the classical-quantum boundary, a missing piece in the old Copenhagen approach, from the rules of many-body quantum mechanics itself. All problems related to the measurement theory have been answered in principle.

People may prefer different philosophies to interpret quantum mechanics - consistent histories; many worlds; the old positivist Copenhagen interpretation - but they ultimately agree about the predictions for all experiments so their philosophies are physically equivalent. What's important is that the predictions may be made for every situation now.

So the measurement problem can't be solved by quantum field theory, string theory, or anything else, because it has been solved for a long time before these newer layers of physical knowledge started to be studied.

Quantum field theory, string theory, theories describing states of condensed matter physics, nuclear physics, atomic and molecular physics, optics, and other subdisciplines of physics that depend on the quantum phenomena take the universal postulates of quantum mechanics as exactly valid principles that cannot be modified in any way.

Modern developments in the research of entanglement, original started by Einstein and his collaborators (especially Bell's inequalities, GHZM state, and Hardy's paradox), have eliminated all doubts that the new quantum description of the reality has to be taken seriously and all "classical" models of the quantum phenomena may be falsified.

So string theory - and even quantum field theory - don't change anything whatsoever about the shared framework of quantum mechanics and its postulates. The question whether our Universe follows the known laws of quantum mechanics has been answered, de facto for 85 years, and most likely, nothing will ever change about these basic matters again.

There is no real problem over here and the postulates of the quantum dynamical framework below will stay with us.

The world is associated with a Hilbert space
Every complex linear superposition of two allowed vectors is allowed
Every observable is associated with a linear Hermitean operator
The squared absolute values of probability amplitudes - complex inner products with eigenvectors of the observables - determine the probabilities that one or another result will be observed
Nothing except for the probabilities may be predicted; it is incorrect to imagine that any physical system that could be affected by quantum mechanics has any well-defined, determined properties (variable quantities) prior to the measurement
Evolution is encoded in the Hamiltonian or the action, via the Schr