Herewith the text of a recent paper.
Truth is ever to be found in the simplicity, and
not in the multiplicity and confusion of things.
Sir Isaac Newton
Introduction
A recent item in Nature suggests that coherent quantum processes may be common in biological systems, contrary to what was generally supposed.
On the face of it, quantum effects and living organisms seem to occupy utterly different realms. The former are usually observed only on the nanometer scale, surrounded by hard vacuum, ultra-low temperatures and a tightly controlled laboratory environment. The latter inhabit a macroscopic world that is warm, messy and anything but controlled. A quantum phenomenon such as 'coherence', in which the wave patterns of every part of a system stay in step, wouldn't last a microsecond in the tumultuous realm of the cell.
Or so everyone thought. But discoveries in recent years suggest that nature knows a few tricks that physicists don't: coherent quantum processes may well be ubiquitous in the natural world.
Why is quantum coherence in the brain surprising for so many? I expect it may be partly due to the persistence of the old classical/quantum distinction, dating back to Bohr. The modern viewpoint has been admirably expressed by Dyson some time ago in his classic article in Scientific American on “Field Theory,” where he writes: “There is nothing else except these [quantum] fields: the whole of the material universe is built of them.”
I have often quoted Dyson’s wonderfully lucid remarks, but lest the point be lost, let me do so again:
Physicists talk about two kinds of fields: classical fields and quantum fields. Actually, we believe that all fields in nature are quantum fields. A classical field is just a special large-scale manifestation of a quantum field.
I believe another difficulty may be a matter of gestalt. Macroscopic systems are composed of myriad quanta—which nonetheless clearly “cohere” into crystals, rocks, plants and animals. It seems to me that, given the basic property of superposition in quantum systems, that we would fully expect a disturbance in one part of the system to propagate throughout. So I expect it is merely a case of people thinking that quantum theory somehow only applies in the microscopic realm. Yet one need not delve deeply into the subject in order to correct this impression, thanks to Richard Feynman:
I would like to again impress you with the vast range of phenomena that the theory of quantum electrodynamics describes: It's easier to say it backwards: the theory describes all the phenomena of the physical world except the gravitational effect [...] In fact, biologists are trying to interpret as much as they can about life in terms of chemistry, and as I already explained, the theory behind chemistry is quantum electrodynamics.
To drive the point home in regard to the brain, let us briefly revisit Umezawa:
When we recall that almost all of the macroscopic ordered states are the result of quantum field theory, it seems natural to assume that macroscopic ordered states in biological systems are also created by a similar mechanism.
Well, yes, of course, it all seems pretty simple when one puts it like that, but then the clarity exemplified by these authors is all too rare.
Another exciting experimental finding may help us form a better picture of what’s going on in the brain. In Schrödinger’s formulation, quantum systems are described by wave-functions [psi]. If the brain just is a quantum field, we might expect this wave behavior to manifest itself on a large scale, and there is now evidence to support this expectation, thanks to the good people at the Max Planck Institute.
Up to now, scientists had assumed that the early stages of information processing in the brain took place gradually, that is that one stimulus was processed after another in a conveyor-belt-like sequence. This idea must now be revised. As Danko Nikolic from the Max Planck Institute for Brain Research and his Austrian colleagues Wolfgang Maass and Stefan Häusler have shown, the activity in early brain areas depends on stimuli that arose some time ago. "The brain functions like a jug of water into which stones are thrown and, as a result, generate waves," explains Nikolic.’ The waves overlap but the information as to how many stones were thrown into the jug and when they were thrown in is retained in the resulting complex activity patterns of the fluid.’
The brain is clearly able to render this information usable and, for example, to superimpose images seen in succession. The duration and intensity of the continuing effect of images that have just been seen corresponds to a very detailed visual memory also known as iconic memory. If you see an image and close your eyes immediately afterwards it remains visible for a short while. It may be located in the primary visual cortex.
These neural waves bring music to my ears. I have often argued that our perceptual images result from the superposition of photons. Pointing to the synchrony observed in neural firings, I have suggested that this behavior would go a long way toward preserving the phase relations among incident photons, without which a faithful representation of the world could not be achieved. That sounds a little technical, but one only has to consider the effect on a symphony if the musicians were to be out of step with one another. Similar considerations apply to photography, of course. We all understand these days that the analogy between eye and camera must not be pressed too hard, but then we must not lose sight of the telling similarities, either.
