Given the complexity of the physics apparently involved in brain state, the "and CPUs can simulate physics" needs to do a lot of work for it to be a practical possibility.

Simulating the physics of dopamine on neurotransmitter cells in silicon is an extremely complicated roundabout way of getting a program to run faster in response to certain stimuli, but most alternatives are likely to fall well short of conveying the full sensory experience of human emotion. And its a difficult goal to know you've hit when even simple text-parsing neural networks which don't attempt to model human sensory experience can plausibly mimick descriptions of it...