What is the cause of the probabilities that appear in quantum measurements? Is the quantum state itself undefined? Is the instrument precision necessary not available? Is the environment unstable?
Quantum Mechanics is not my faith, but I think the probabilities come about because it is easier to explain results of massive amounts of happenings by using statistical probability. The QM faithful take the easiest path; you have to admit QM is the most successful set of theories that has come down the pike in awhile.
Quantum probabilities are due to the universe being acausal & probabilistic. Read about and think deeply about radioactive decay. It is modeled exactly by a poisson probability distribution. In some of its aspects, it can be modeled by a binomial probability distribution. Radioactive decay is only one quantum process which is probablistic. The best theory for such processes requires viewing them as acausal and governed by probability laws rather than deterministic laws. It is counter intuitive to view reality as capricious, but the evidence points that way.
Ultimately, it is just how the universe works. It turns out that we can't know everything about the universe to unlimited precision. Nobody really knows why. The Heisenberg uncertainty principle is one example of how quantum probabilities manifest themselves when we make measurements. Quantum states are well defined. But when measurements are made on those states, the outcomes of those measurements are random, within certain bounds set by the states themselves. Quantum uncertainty is not totally about instrument precision. It goes deeper than that. Quantum mechanics tells us that no matter how precisely we try to measure certain quantities, we will never be able to predict the outcomes of those measurements with certainty. In a sense, it says that ideas such as position, velocity and energy become fuzzy at very small scales.
