Unfortunately it appears that it is physically impossible for there to be a quantum computational aspect to the brain.

For a while I thought that perhaps the “conscious” (i.e. classical computer) part of the brain could act as the “observer” and by an “entangled Quantum Zeno effect” it could make the decoherence time of a brain quantum computer sufficiently long to be physically possible. The Quantum Computer part of the brain would correspond to the “sub-conscious”. Sadly, a discussion with perhaps the greatest theoretical Quantum Physicist on the planet shows that this is not viable 🙁 It therefore appears that there is NOT a quantum computational aspect to the brain.

And just today the bloody obvious hit me like a hammer. If there WAS a quantum computational aspect to the brain – then why would we be stymied by the 2-slit experiment? And more importantly why would Feynman have been able to say that “nobody understands Quantum Mechanics”?

Looks like the brain is a massively parallel classical computer, still it gives very impressive results!!

But I think Roger Penrose showed that it is NOT a Turing machine.

Looks like there are as many papers out there saying the brain is a Turing machine as there are saying it isn’t. However, I don’t know enough about Turing machines to know whether this tells us anything interesting or not about brain function. Maybe you could enlighten me 🙂

The main problem I have with any brain/Turing machine comparison is that “a Turing machine is just a model of computation; it’s not physical. Saying a brain is a TM makes as much sense as declaring it to be a well-formed formula”.

As I remember it, Penrose argues that the brain can compute the answer to a problem that a Turing machine would take an infinite time to compute (Goedel’s theorem?). It was in the Emperor’s New Mind – probably quite dated by now, but I think he was attracted to a quantum involvement in the brain too.

I thought you might have read it there 🙂 I was so totally fed up with that book it was the only book I have ever given away. Penrose teamed up with a mate of mine, Hameroff, to work out a possibility of a Quantum Computer brain based on microtubules. In a brief discussion with David Deutsch I can assure you that there is no way there is a Quantum Computational aspect to the brain – a fact that I am personally gutted about.