Re: What about the brain?
There is no reason to expect brain replacement to require quantum physics. The standard rejoinder is that the brain is "warm, wet and noisy", all of which tends to break quantum relations rather quickly. There may be isolated parts of the brain that use quantum physics for chemical processes, but there is no evidence for the notion (and lots of evidence against) that the brain uses quantum physics for computation.
As a result, it should be possible to replace the brain with a digital simulation. Computer capacity worldwide is starting to enter the ranges of power where such a thing begins to look feasible, depending on the complexity of simulation required. (Which should also not be too high, again due to the previous argument - "warm, wet and noisy" also limits the computational complexity that is being employed.) The first attempt will of course cost billions. Then millions. Then tens of thousands...
Biting the hand that feeds IT
