[kibwen]

> nearly every technological breakthrough in history has been accompanied by plausible-sounding arguments as to why it should have been impossible

Indeed, and at the same the breakthroughs are vastly outnumbered by ideas which had plausible sounding counterarguments which turned out to be correct. Which is to say, the burden of proof is on the people making claims that something implausible-sounding is plausible.

[lisper]

But QC is quite plausible. There is no theoretical constraint that makes it impossible. It really is just an engineering problem at this point.

[kibwen]

But the distinction that we're trying to make here is that people hear "plausible in theory" and think "plausible in practice within the timespan of human civilization", which does not follow.

I'm not trying to say anything about whether or not a CRQC will ever be built. I'm also not trying to say that pursuing PQC in the short term is a bad idea. But what I am saying is that the burden of proof remains on the believers to show that the engineering challenges are more than theoretically surmountable.

[lisper]

Yes, of course that is true. When I said that QC is "just an engineering problem" I did not mean to imply that it was straightforward. It's not. It's a Really Really Hard engineering problem with a lot of unknowns. It might turn out to be like fusion, perpetually 10-20 years away. Or it might turn out to be like the blue LED, seemingly impossible until someone figured out how to do it. I think you'd be foolish to bet your life savings on it either way.