Quantum exists in the extension as we created the concept. It was an useful idea created by Planck and explored by Einstein. It is impressive how one person's ideas can influence all Physics. All Physics is now contaminated by Einstein's views.
Recently Prof. Robitaille published a paper invalidating Kirchoff's Law and by extension, Planck's constant h looses its universality.
In the last 100 years QM comes a long way from quantum creation. I don't think they'll return back to verify any possible mistake.
Theories are models, in Hamiltonian space is possible to mathematically describe various. My point is not invalidate the mathematical model, but its connection with our perception of reality. This is a philosophical question. If a theory is incompatible with our perception, with our capacity to understand the universe in which we live, so this theory is not useful.
Then a question arises and the answer is a choice. There is a fundamental identity between the human mind and the reality in which we live? My choice is Yes. Hence, as consequence of my choice, a fundamental reality can exist. So I can say that human Logic is a expression of existing process in physical reality.
I'm not referring to a person's train of thought, but to a fundamental organic human Logic.
Accepting Logic, the only valid process of knowing the universe becomes deterministic.
The wave function always will collapse in reality. The probability is only expressing what we don't know. Knowing is always a local and deterministic process.
When a mathematical theory Interpretation produces paradoxes, is a clear indication that the Logic was violated.
Let's examine a classical QM experiment, the EPR. We can substitute the particles by balls and the spins by colors, named black and white. The balls are created in pairs, one is black and other is white. We put each ball in one box and separate the 2 boxes for a great distance, 100 light years for instance. We call boxes A and B. One observer open the box A and see the ball inside is black. QM Interpretation states that the information travel instantaneously to box B and the ball "becomes" white!
Is that logical? No. Logic says that the information was already there at the moment the balls were created, so the velocity is zero. As any 5 years old children can understand.
QM superposition Interpretation says until the boxes were open the balls were grey.
Logic says, No. There is no valid superposition of eigenstates. The only valid colors is black Or white.
The only way to entanglement become valid is if a real change in one ball produce a change in the other. Say we change the color of one ball and instantaneously the other color changes.
Transcendental Interpretations violate Logic.
There is a general sensation that QM departed from Logic a long time ago. If QM is not logical anymore, then it is useless.