I had the same question as grandparent. Thanks for the links, and maybe I'm not getting this because it's just way over my head, but this article seems to assum

I had the same question as grandparent. Thanks for the links, and maybe I'm not getting this because it's just way over my head, but this article seems to assume that because the non-quantum computers of today can't simulate complex (particles numbering above ~Avogadro's number) quantum systems, they can't exist. This sounds like the article is claiming that the universe is a computer simulation, or that stuff can't exist if we can't compute it. Can someone please help me understand why something being able to exist in our universe depends on if we can calculate the physics for it, or where I've gone wrong in getting to this question?