Well the calculations to do this elimination would have to happen somewhere. Deutsch and the many-worlds interpretation says it happens in parallel universes. And what makes quantum computing so difficult is that you have to arrange those parallel universes to be identical in every way except the inside of the computer itself. That's the only way to get an answer back. If there's interference with the outside environment, the universes become different outside of the computer and you can't get an answer back.

I love this stuff.