That is an excellent question! And the answer is that when you do the math, the result of taking a subset of the wave function (the mathematical operation is called a "trace") is something that looks like a classical system. If you want the details, see this paper:
Yes.
> If so, how can we talk about discrete systems.
That is an excellent question! And the answer is that when you do the math, the result of taking a subset of the wave function (the mathematical operation is called a "trace") is something that looks like a classical system. If you want the details, see this paper:
http://www.flownet.com/ron/QM.pdf
Or this video
https://www.youtube.com/watch?v=dEaecUuEqfc
which covers the same material.