rasp said:
The basic assumption, which seems extremely plausible based on our current understanding of the brain and of decoherence, is that quantumstates corresponding to distinct conscious experiences have to be orthogonal.
Our current understanding of the brain and decoherence puts the decoherence time at less than 10^-13 s (Tegmark's calculation). That's too fast for chemistry. Molecules in water bump into each other slower than that. (on the order of picoseconds) It's like saying it's plausible that the speed at which you swat flies is determined by the motion of air molecules.
The body is chemical. Whatever you believe, you still have to admit that whatever the brain does, the majority of the stuff it does is due to chemistry.
One of Kak's lines of reasoning is this, "Quantum theory has the potential to provide understanding of certain biological processes not amenable to classical explanation. Take the protein-folding problem. [...] Yet Nature solves this problem in a few seconds. Since quantum computing can be exponentially faster than conventional computing, it could very well be the explanation for Nature's speed
Frankly, that's idiotic. Nature doesn't perform calculations, nature just is. There are
plenty of phenomena (and perfectly classical ones) that are exceedingly difficult to calculate. The idea that it'd take 10^127 years or so to calculate the conformation is an estimate made on the basis that it's a combinatorial analysis. Form every possible configuration and 'test' it. That's not what happens. A ball at the edge of a bowl does not try out every possible place it could be, decide the bottom is the best, and goes there. It just rolls down the slope.
But let's just pretend for a second that nature really does 'calculate' every possible protein configuration. How does it 'know' which answer to choose? Thermodynamics would say it should then choose the lowest-energy configuration. They don't. Proteins in living organisms almost
never have their lowest-energy conformation. The lowest-energy configuration is a random mess. Proteins are folded to a specific ordered shape. They are in a
local minimum, not a global one. Biological organisms go to great lengths to ensure that they 'find' the right local minimum of the millions of possibilities, by providing specific environments and 'chaperones' for the protein to fold in. It can take dozens of helper proteins to produce just one complicated one.
If proteins could exist in a big superposition of possible structural conformations, they'd denature themselves. Eggs would instantly turn hard-boiled. We'd all be dead. This is all contrary to very well-known experimental evidence: Most chemical isomers are quite stable. Not even small molecules exist in a superposition. To take the original example of Biot and Pasteur: D-Tartaric acid is D-Tartaric acid, every time you look at it. It does not spontaneously become L-tartaric acid. There's no superposition of D and L forms going on. It's simply ridiculous to think that a protein molecule 1000 times larger could do so. The smallest possible chemical 'unit' - a single hydrogen atom, which in some circumstances
does tunnel or form a superposition, still behaves mostly 'classically'. I can dig up the numbers if you like, but it amounts to little more than a correction to the calculated speeds of hydrogen kinetics.
Quantum computing is great for combinatorial problems, but it's not a combinatorial problem. It's a dynamical problem; the many-body dynamics of a huge system. Those are hard to calculate, even when purely classical. (and when protein-structure calculations are done in the real world, it's with an essentially classical model)
Whatever, he's been paid more than you and so passes one of your rules for respectability.
I didn't say respectability had anything to do with getting paid.
You alleged that I'm somehow averse to speculating on quantum effects in biochemistry. I was merely pointing out that, not am I not averse to (credible) speculation, but as someone who's worked with it, I can claim to have been paid to do it.
But I do not work for a department of philosophy. I work for a department of physics. I don't get paid unless I accompany my speculations with either calculations or experiments. JACS isn't going to accept a paper consisting of little more than worded argument. (at least not unless you sneak it into a review article or something)
I thought I made the point earlier: It's nto about respectability. It's about
expertise. And to the extent that I know anything about anything, the thing I know the most about, is how chemstry and quantum physics relate - and even more specifically, in biochemistry.
Penrose isn't a 'persona non grata'. He's a gifted mathematician who did indisputably important work with Stephen Hawking. I'm happy to hear his opinion on black holes. But I'm not going to rate his speculation on the quantum-mechanical actions of proteins higher than the experiences of those who are experts at doing quantum mechanical calculations on proteins.