Over at Shtetl-optimized Scott discusses some ideas about biological brains and quantum computers.
I commented on the post, thought I’d reproduce the comment here:
It’s suspected that the class of substances known as neurotransmitters (like seratonin) play an important role in defining human behavior.
Just focusing on seratonin: this molecule undergoes a variety of chemical reactions, from its formation through to its binding with receptors in the brain.
Just focusing on the binding reaction: seratonin binds to a certain class of receptors.
If you treat the molecule and the receptor at the Hartree-Fock level, the molecule never binds with the receptor.
(This failure to bind isn’t restricted to this example. An entire class of important reactions (those catalyzed by enzymes) has this feature).
In order to capture the mechanisms responsible for binding, aspects of the binding process need to be treated with more accurate quantum mechanical models, for example coupled cluster methods.
Anyone who claims quantum mechanics is not directly involved in human behavior (which is of course related to consciousness because it’s the only evidence we have for anything related to it) has to explain how a human could be conscious without the ability for any of their neurotransmitters to bind to the receptors in their brains.