Firstly, you're going to run into walls if you try to fully understand why the mathematics of quantum mechanics are how they are. Physicists have been going at

Firstly, you're going to run into walls if you try to fully understand why the mathematics of quantum mechanics are how they are. Physicists have been going at it for decades and from what I can tell the picture is not so clear yet. What has been done though is many thousands of experiments showing that the predictions the mathematical theory makes (even the wild, unintuitive ones) are correct. Secondly, I think you're going too deep on this whole 'prediction' thing. The algorithms in quantum computing aren't trying to model something any more than a classical algorithm does. Currently, the notion of a quantum algorithm is just a series of special logic gates that act on qubits instead of bits. What the previous poster said above is correct. Quantum computers are like classical computers with randomization except instead of real probabilities it has what are called complex amplitudes. The way the complex amplitudes behave allow for the states to interact slightly different since they can now 'interfere' with each other to cancel each other out in very specific situations. This power gives quantum computers only slightly more power the classical ones (with randomization). (Most) experts don't think quantum computers can solve NP-hard problems. This power from the interference only helps in very specific problems.