This comment and GP are two of the most concise and punchy descriptions I've ever heard of some of the deepest aspects of modern physics. On the one hand we have principles of locality and finite propagation speed, which limit the computational work to a small neighborhood, and on the other hand we have principles of non-locality and superposition, which cause the computation to explode as it swallows up potentially everything and every possible thing.

Not necessarily.

You'd be correct given hidden variables.

But we know pretty convincingly that quantum anything does not have hidden variables.

https://en.wikipedia.org/wiki/Bell%27s_theorem

But only if someone observes it. The act of observation forces reality into existence.