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Comment by AndrewStephens | Hacker News Reader

> gate fidelity and other parameters are above certain threshold

A threshold that might be beyond what the physical properties of our universe allow. It is still unclear.

This is what bugs me about both quantum computers and commercial fusion power. There's so much talk about how it's just inevitable and will happen soonish, but a lot of the evidence suggests, in some cases strongly, that it might not ever be possible.

I find it weird how bleeding edge research, at the very edges of both physics and engineering, is treated as though it's a market development about to drop. Possibly a consequence of pure R&D having all but died? Getting funded requires pretending there's a business plan for what you're working on?

There's no strong evidence of impossibility. For quantum computers to be impossible at scale we need new unknown physics. Fusion requires lots of engineering. And before those engineering efforts would show practical impossibility or impracticality, there can't be strong evidence.

By not ever be possible, I mean in a practical sense, including e.g. the economics of it, as well as reliability, checkability, etc.

Jassby's article about fusion (https://thebulletin.org/2017/04/fusion-reactors-not-what-the...) describes several well-understood issues that could prevent commercial fusion power from ever being practically possible.

For quantum computers, the situation is quite similar. Michel Dyakonov and several others have laid out the situation well.

At least we don't have anyone claiming that interstellar travel is just 10 years away, yet. Probably because it's more difficult to make an economic case for it. But the issues are quite similar. In principle, in terms of physics, nothing prevents an interstellar journey. In practice, it just isn't going to happen.

This possibility means discovery of new physics that has no indications of existence yet.

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