> there are known physical phenomena, such as quantum entanglement
QC researcher here, strictly speaking, this is false. Clifford circuits can be efficiently simulated classically and they exhibit entanglement. The bottom line is we're not entirely sure where the (purported) quantum speedups come from. It might have something to do with entanglement, but it's not enough by itself.
Re: about mermin's device, im not sure why you think it can not be simulated classically when all of the dynamics involved can be explained by 4x4 complex matrices.
QC researcher here, strictly speaking, this is false. Clifford circuits can be efficiently simulated classically and they exhibit entanglement. The bottom line is we're not entirely sure where the (purported) quantum speedups come from. It might have something to do with entanglement, but it's not enough by itself.
Re: about mermin's device, im not sure why you think it can not be simulated classically when all of the dynamics involved can be explained by 4x4 complex matrices.