Now it's far from the first time the Huffington Post has gone off promoting bad science, pseudoscience or outright crankery, having for instance lent its voice to Jim Carrey (in his latest role as an immunologist) preaching the 'dangers' of vaccines. I'm not the only one around here who seems to think they've grown increasingly sensationalist as well as anti-science (although this is more in the realm of 'bad science').

(So in the bigger perspective, I guess it's not that bad as far as these things go. Unlike vaccine scares, it's not likely this particular nonsense is going to lead to unnecessary deaths, for instance.)

The reason why I'm relatively qualified here, is that I'm a quantum chemist who studies biochemical systems. In short, I apply quantum mechanics (QM) to figuring out how chemistry works, specifically biochemistry. So I'd hope to know something about the subject. On the other hand I don't really want to appeal to authority alone. (Being somewhat pseudonymous, you've got no real reason to believe in my authority either. But do feel free to ask about quantum chemistry! :) )

"Quantum consciousness"

Is basically what he's talking about. The idea that the workings of the human brain are somehow directly quantum-mechanical. As opposed, I'd guess, to being 'chemical' in nature.

Chopra would count as one of the more high-profile promulgators of this idea, which exists in various forms. The probably best-known advocate (perhaps deserving the credit as 'originator') of this line of thinking is mathematician Roger Penrose. The proponents have different ideas, ranging (in my opinion) from 'fringe' to 'just doesn't know what they're talking about'. Penrose belonging to the former group, Chopra the latter. I think it's highly relevant that I don't know anyone in my field who takes these ideas seriously. (Much less Chopra) Attempting an explanation...

About quantum mechanics

Okay. So, quantum mechanics is infamous for being 'weird' and 'difficult'. Which is true to an extent. But to another extent, the subject has been bogged-down a bit by its own reputation. The early pioneers of the subject (Bohr & co) got into big debates over how the subject should be 'interpreted', a discussion which has gotten carried over into many introductory textbooks (and practically every popular-scientific account) ever since. In a letter to the American Journal of Physics last year, N.G. van Kampen called it "The scandal of quantum mechanics". (incidentally the letter also took a dismissive swipe at quantum-conciousness theories) So in your popular-scientific descriptions people have often confused actual QM (which has not been at dispute) with these 'interpretational' issues.

I'm not going to even attempt to correct the very many misconceptions that abound about QM here, or attempt a popular-scientific explanation. I'll basically just make a one short point.

This is the one quantum-mechanical property that's relevant to this discussion, which is that in quantum mechanics, things can exist in several states at once. (called a superposition) Objects don't have definite locations; rather they're 'smeared out' over space. The lighter they are, and the faster they move, the more 'smeared out' they can be. (those who've read about QM before know I'm referring to the famous Uncertainty Principle)

But if a measurement is carried out on the object, it will have a certain value. Which is part of the 'weirdness'. QM cannot predict what value will be measured, but it can predict the probability of all the possible measurement results. It can predict the average of a large number of measurements. For instance, the electron of a hydrogen atom is most likely to be 53 picometers away from the nucleus. But a single measurement could give any result from zero to infinity.

Heavier, bigger, things on the other hand, get less and less 'smeared out', and you end up with the 'classical' situation, where things assume definite values for their location and speed and other things.

Chopra (and many, many others) misinterprets what 'measurement' means here, assuming that it has something to do with human activity, drawing not only the erroneous conclusion that human (or sentient) perception is what's meant by 'measurement', but indeed that things don't even exist if they're not being 'measured'. Stating: "In fact, everything you are looking at right now depends upon you to exist."

This is a basic misconception which has been debunked repeatedly (no doubt several times a week on physics newsgroups and message boards). Quantum mechanical measurements have nothing to do with 'measurement' per se, and especially not with human activity. It's also at the basis of the Schrödinger's cat 'paradox', as well as many of the early confusion about quantum mechanics.

In short, it's a process known as decoherence. It's not fully understood yet (although a lot of progress has been made since the early days and early confusion of QM). Decoherence is the process whereby quantum systems go from a superposition of different states to a single, definite state, through interactions with their environment. It's 'locked' into this state because there's an increase in entropy (disorder) associated with that change, making it irreversible (2nd law). It's not fully understood yet, but it certainly doesn't resemble the Berkleyian idea Chopra seems to have adopted.

Chopra's version is:

Light can act like a wave or a particle, but not both at the same time. It defies ordinary logic, but Einstein and his colleagues discovered that light "decides" whether to act like a wave or particle depending on the observer.

What he should have written was "in the context of the double-slit experiment", because there's not really a state of 'acting like a wave' and 'acting like a particle'. Although I see how he'd get that impression given that most popular-scientific accounts present the double-slit experiment.

It does not defy ordinary logic. Quantum mechanics, like all physics, is entirely founded on ordinary mathematical logic. Einstein had little to do with the development of quantum mechanics (his contribution basically being his early 1905 paper on the photoelectric effect), and was famously critical of it.

The particle does not 'decide' depending on the observer. Rather in the double-slit experiment, the interaction involved with making the measurement causes decoherence, forces the particle from having had an indefinite location (causing it to act 'like a wave' - forming a superposition), into a definite location (which we associate with 'acting like a particle')

As opposed to what Chopra writes, the brain is assigned no unique role whatsoever in causing decoherence and frankly, it's pretty silly to assume that physicists (or anyone, really) would adhere to such a ridiculously anthropocentric idea.

Why it's wrong

Chopra, Penrose and other proponents basically all work on the assumption that something in the brain is acting quantum-mechanically, i.e. existing in a superposition of states. In addition, some of them argue that the brain is therefore a quantum computer (a 'computer' which utilizes these superpositions to perform certain types of calculations very quickly).

The mainstream view doesn't agree with this. The mainstream view being that the brain, just like everything else we know of in the body, is governed and controlled by chemistry. Chemistry is in fact intrinsically quantum mechanical in nature. Quantum mechanics was in fact developed, not primarily to solve the the problem of the double-slit experiment, but to explain atoms. As far as classical physics is concerned, atoms could not exist!

So if you want to do the theory of chemistry: What's a chemical bond? How does a chemical reaction occur? and so forth, you're dealing with questions that are answered by quantum mechanics (and quantum mechanics alone).

You learn in school that atoms and molecules consist of nuclei surrounded by electrons. The nuclei carry most of the mass (weighing thousands of times more than the electrons) and a positive charge, but chemistry is entirely dictated by the behavior of the electrons. The nucleus just sits there - the effect of its charge on the electrons being its contribution.

The electrons act almost entirely quantum-mechanically, which is why QM is required to describe chemistry. But the nuclei don't act very quantum mechanically - they're too heavy.

So, while the electrons in a molecule act quantum mechanically, the molecule as a whole does not. The atoms of a molecule almost never exist in superpositions of different states. If they could, many molecules and compounds would not be stable over time. They'd rearrange themselves. A lot of the molecules in your body would spontaneously combust, rearranging themselves into lower-energy forms.

(Chopra, OTOH, claims: "However, our every action alters DNA". It does? In what way?)

(Part of) The reason this doesn't happen is that molecules aren't isolated. They interact with their environment (which in QM, constitutes a 'measurement'). They undergo decoherence, forcing them to stay in the state they're in.

This is pretty unsurprising, since if molecules as a whole could act quantum-mechanically like that, we'd probably already know about it from chemistry. See, while quantum mechanics forms the theory of chemistry, it hasn't actually lead to a lot of new discoveries (yet). (Nor is there much, if anything, in biochemistry which is fundamentally unique to biochemistry)

On top of that, I have biochemical objections: That so far, we've not seen any such quantum things going on in any of the biochemistry we do know well - it's unusual for things on the biochemical scale to be really, really different. We share a substantial portion of our DNA with the lowliest of bacteria. Our cellular metabolism isn't that different from an amoeba. Evolution causes nature to 'recycle' its designs. Enzymes with very different functions can have very similar structures due to common evolution. From an evolutionary standpoint, it'd be rather strange if our brains somehow started utilizing a completely unique physical phenomenon.

Nevertheless, physicist Max Tegmark (who's actually a cosmologist, but OTOH something of an expert on decoherence) did the math on some of these quantum-consciousness models and got the result most of us expected: The systems decohere far too quickly (on the order of 10-20 seconds) for it to have any impact on chemistry, much less biology (neuron firing taking place on the order of milliseconds).

Schlosshauer, "Decoherence and the quantum-to-classical transition" (2008) devotes a segment to this controversy and concludes (p374):

It is fair to say a majority of researchers now uphold the view that biological structures in the brain are most likely too prone to decoherence to allow for any quantum coherence to persist over timescales relative to cognitive and conscious processes. Therefore classical models of the brain remain largely unchallenged to date. Based on Tegmark's numerical results and general intuitions about decoherence on macroscopic scales, it is unlikely that this situation will change anytime soon.

Philosophical objections

This refutation hasn't really stopped the proponents of these quantum-consciousness theories, who've continued to look for new ways to somehow link the brain to quantum mechanics. It's hardly a surprise, really. They wouldn't be stopped by that, because they didn't really have any particular scientific reason to formulate such a theory in the first place. Basically, it's a solution in search of a problem.

The fact that we don't know how consciousness works is, after all, just part of the fact that we don't know how the brain works. We don't know how the spleen works either, for that matter. We've mapped the genome but we don't even know which genes are associated with which tissues. So it's not a reason in itself to go looking outside of existing biology and chemistry for an answer to an unsolved question, especially considering how the existing paradigm is doing quite a good job.

Making up a theory without any particular basis for doing so and then go looking for evidence (and/or ways to make your theory work) is a hallmark of bad science and psuedoscience. So is sticking to your theory once it's been disproven.

As for Chopra, well at least he knows more science than L. Ron Hubbard did.

(Damn that was long, thanks for taking the time, if anyone made it this far!)

Update: Rec list? Thanks! I would never have expected that for such a 'niche' (and far from easy) subject!