The device cannot be accurately simulated using a classical computer because it relies on quantum entanglement that has no counterpart in classical physics. The results cannot be simulated even if hidden local variables are used.

The only way to simulate accurately on a classical computer is to use global state but this goes against the instruction that the devices must be isolated from each other.

> This is immaterial, however. It is a well known fact that BQP is in PSPACE and Clifford circuits (a subclass of quantum circuits) can not only be simulated classically, but done so efficiently. It is not controversial.

Yes, BQP problems are solvable and a "subclass" of quantum circuits can be simulated efficiently. But the fact is there are known aspects of reality that cannot be simulated on a classical computer.