…Gil and other modern skeptics need a theory of physics which is compatible with existing quantum mechanics, existing observations of noise processes, existing classical computers, and potential future reductions of noise to sub-threshold (but still constant) rates, all while ruling out large-scale quantum computers. Such a ropy camel-shaped theory would have difficulty in passing through the needle of mathematical consistency.That is saying that it is hard to construct a mathematically consistent theory that excludes quantum computers. But it is also hard to construct a mathematically consistent theory that includes quantum computers.
My FQXi essay tries to explain the foolishness of this "needle of mathematical consistency" argument. There is a similar argument about Bell test experiments. They are unremarkable except that many physicists and philosophers find that they conflict with their prejudices about mathematical needles, whatever they are.
His comment is like saying that gravity is impossible because it is hard to see how quantum gravity would pass through the needle of mathematical consistency. People are always making weird consistency arguments about quantum mechanics. If your take those people seriously, then there is no reality. But you take them just seriously enough to believe in quantum computers? I say that quantum computers are impossible.