[dasimon]

I am no expert, but it sounds to me like this headline is an oversimplification.

The abstract of the paper suggests that the authors intend to support the claim that "not all quantum systems can be simulated efficiently using classical computational resources". Essentially that it's impractical to simulate complex nondeterministic quantum behavior using deterministic algorithms.

But what about quantum computers? It would seem to me like their inherent nondeterministic behavior would be an ideal fit for simulating other nondeterministic quantum systems.

In any case, it doesn't sound like they found any real theoretical limitation, just a practical one.

[SigmundA]

Why does matter whether it is simulated efficiently? What if each Planck time or frame takes a huge amount of "real" time to simulate, we would not know it.

Think of a Pixar render farm that takes hours to render one frame, the characters inside would not know that, their world unfolds in real time to them.

[foxhill]

> But what about quantum computers? It would seem to me like their inherent nondeterministic behaviour would be an ideal fit for simulating other nondeterministic quantum systems.

true, but in this case now you either need a computer the size of the universe to simulate the universe in real time, or you can simulate a universe in (incredibly small) fractions of real time in a system less than the size of the universe.

this doesn't even get around the state-storage problem - storing the state of a simulated universe (assuming literally zero-overhead) takes the entirety of the universe too.

> In any case, it doesn't sound like they found any real theoretical limitation, just a practical one.

and therein lies the kicker :)