It's more akin to "we only need to make reliable transistors to make classical computers." With the invention of the planar transistor, going from 1 transistor to 100 or 100k was not that big of a step, comparatively.
It's really really easy to eliminate noise in a digital system of transistors. For analog systems with subtle values, I would say we still can't arbitrarily scale that up with transistors. And quantum is like analog but far worse.
It's really really easy to eliminate noise in a digital system of transistors. For analog systems with subtle values, I would say we still can't arbitrarily scale that up with transistors. And quantum is like analog but far worse.