We have quantum mechanics but quantum computers have been late in coming, suggesting that our universe would be difficult to simulate.
Quantum computers are computers which use quantum superposition for parallel processing, and are not required for simulating quantum mechanics. And our "classical" computers do in fact take advantage of quantum mechanics, as classical physics does not allow for solid state transistors.
And our "classical" computers do in fact take advantage of quantum mechanics, as classical physics does not allow for solid state transistors.
I don't understand what point you're trying to make here, but classical physics allows for mechanical computers.
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