I'm aware and agree that quantum computer speed is very probably greater than classical and may allow some NP. My point is more that I'd expect the performance cost of QM to equal the complexity class of QM. I don't know, is that the case in current research? Whenever people talk about how expensive it is to compute QM, that always sounds a lot higher than the actual performance they get back out. Or maybe I just have a bad imagination for how high NP really is.

Disagreeing again with the "Ansible is unrealistic" view: I agree it's unrealistic in a global sense, I just think all of its unrealism comes from the use of FTL in the backend. FTL + relativity produces timetravel, yes. I just think it's implausible to expect a physical universe to first provision the mechanics for FTL, then provision a system that gives you timetravel when exposed to FTL, and then very carefully separate those two systems so that they computationally never touch, even though in theory they could! and so in a sense, this physical theory implies that this universe has to be prepared, in principle, to allow time travel and account for it, and having gained this capability has elected to specifically not use it. It just stinks of a massive Occam violation - the potential for time travel is an "entity without necessity", and the theory is bloated by it twice over; once by its inclusion in the physical logic and once again by the additional exclusion mechanism that makes it unusable in every reachable state. And so the ansible universe pays slightly less cost just by leaving out the global censor.

Am I saying "no correct theory can look like this"? No! I am saying it enters the race with a huge handicap.