Of Minds, Entanglement and Coherence – Quantum entanglement
Simon Raggett has been working hard to explain how quantum effects might work in the “noisy” environment of our animal minds. This is a very new area and one at the very edge of current research. The label “quantum Biologist” has only just been coined. This is a very readable article that helps show where we are and where we are going
Richard Nissen
Editor
Quantum entanglement is the only known feature of physics that has even a tenuous likeness to the properties claimed for psi or remote communication between either humans or animals. However, this does not justify any vague talk of a connected or entangled universe, as an unrestricted catch-all for whatever we choose to suggest. There are strict constraints as to what entanglement can and can’t do. Even conventional literature with references to teleportation and quantum information can sometimes seem to imply more than is really justified.
Quantum entanglement indicates that where two quanta have become sufficiently closely related, such as for instance two electrons in the same orbital, then a fixed correlations or relationship is established between them. For this entanglement to exist, it is necessary for the quanta to be in a coherent state, meaning that they are in a superposition of different possible states. In the case of our electrons, they can be viewed as being in a superposition of two possible spin states, spin up and spin down, or as having a possibility to come into either spin up or spin down state. The next step is that our electrons become separated. This separation can be over any distance, ranging from the other side of a laboratory bench to the other side of the universe. They are, at this stage, still in a superposition of spin up and spin down. The next step is that one of the electrons is measured, or in more modern scientific parlance, decoheres, as a consequence of interacting with the environment. At this point, it ‘chooses’ between the two superimposed spins, and for this example we shall say that it ‘chooses’ spin up. This is where the fixed correlation between the electrons kicks in. Once the first electron ‘chooses’ spin up, the other electron will also decohere, and its spin will have been in effect preselected for it by the first electron. If the fixed correlation happens to be that the electrons would always have opposite spins, the other electron will find itself with spin down. This is effective over any distance, and just to make matters worse, it is instantaneous.
How should we interpret this, or relate it to our understanding of the universe? Einstein originally proposed this as a falsification of quantum mechanics (EPR experiment, 1935), but experimentation in recent decades has repeatedly supported the concept as being a real process. Entanglement theory proposes instantaneous transmission over any distance. However there are strict constraints on what can be instantaneously transmitted. Energy and by extension matter cannot be transported in this way. As a result, information as we would normally define it, which is instantiated in energy or matter, such as the electrons in a telephone cable, cannot be transmitted by means of entanglement. It is because of this that entanglement is not considered to violate relativity. It appears that all that can be determined by entanglement is the spin or polarisation of quanta, notably the spin of electrons and the polarisation of photons. Even the mass and charge of quanta, albeit that these are fundamental properties, cannot be determined by entanglement. This somewhat qualifies the mainstream references to teleportation. It appears that all that is actually transmitted in teleportation is the spin of electrons. This is considered to represent the teleportation of a quanta because all quanta of a particular type have the same mass and charge, so by shifting the spin of a quanta, one can be argued to have teleported the whole quanta.
Entanglement and spacetime
For the interpretation of what is going on here, I will simply make a suggestion aimed at rendering the concept less puzzling or counter intuitive. This is that entanglement might be easier to come to terms with, if we decide to treat spacetime as the fundamental aspect of the universe. This does not put us outside of mainstream physics, although the majority of physicists probably favour the alternative of regarding the quanta as fundamental and spacetime as a product of the quanta.
However, it seems that if we regard spacetime as fundamental, some things may this become easier to comprehend. In considering how the brain represents the external world to us, it becomes arguable that our notions of space indicate something more fundamental than the quanta. It is a commonplace that the external world bears no resemblance to the images that our brain represents, because the external world comprises only quanta of energy fluctuating in the vacuum. Furthermore the quanta lack a convincingly fundamental nature given an ability to annilate one another or disintegrate. When we consider space, the situation is slightly different. It seems that our perception of space must relate to something real, as there has to be some interval or separation between the aspects of the world, albeit that they are merely arrangements of oscillating energy packets, otherwise we would be living in a singularity.
The representation in our brain can be compared to the map of an underground railway system. The two dimensional system of lines on a piece of paper bears no resemblance at all to the concrete tunnels or metal vehicles of a rail system. However, the representation on the piece of paper of some stations as being further away from the city centre does have, an albeit very distorted, resemblance to the spatial distribution of the city. I think this difference might be trying to tell us that spacetime is the fundamental aspect, and the quanta less fundamental as mere disturbances of, or oscillations in, spacetime. A recent experiment helped to demonstrate spacetime as a reality rather than an abstraction. When an electron was accelerated to one quarter of the speed of light, its energy produced photons out of the quantum vacuum. This confirmed the more descriptive suggestion that observers on a spaceship accelerating towards a significant percentage of the speed of light would see hot particles coming towards them out of the vacuum.
This might not carry all that amount of weight as an argument, if it was not that positing space, or more correctly spacetime, as fundamental does make it rather easier to come to terms with the concept of quantum entanglement. This has had a mind boggling quality for many because the idea of instantaneous transmission over any distance conflicts so much with our other notions about physics, even if it does not strictly conflict with relativity. However, it becomes less difficult, if we regard spacetime as fundamental. The light speed limitation of special relativity applies to the movement of mass and energy, but this constraint does not appear to apply to changes in spacetime itself, so if the entanglement is seen as an aspect of spacetime the existence of instantaneous transfer over distance appears less problematic.
There is now a fairly general view that spacetime is not continuous, but is instead quantised. This view derives from it being easier to achieve compatibility between quantum theory and relativity if spacetime is also quantised. In the last century, Roger Penrose hit on the idea of spacetime as a ‘spin network’ with spin as the only true quantum property, presumably because it is the one the can be transferred by entanglement, as distinct from mass and charge. With this approach, it is possible to view spacetime as a weave or fabric, with the quanta at the nodes of the weave. Penrose’s spin network concept is similar to the more recent loop quantum gravity theory, a rival to the more popular string theory.
As an analogy for our suggestion of how entanglement might operate in spacetime, it is possible to think of spacetime as a bit of cloth. When we shake this out, for the purposes of everyday perception, the movement is seen to be transmitted instantaneously. However if the cloth has a pattern, although the material may stretch or twist, the features of the pattern remains the same number of stitches or distance apart; they are thus more constrained than the fabric of the cloth, in the same way that particles with mass or energy are more constrained than spin or polarisation.
Quantum coherence in organic matter
Our description of quantum entanglement, given previously, follows very much a conventional text book approach. However, it may be that the emphasis of such descriptions misses the really important aspect of entanglement. Attention in such descriptions tends to focus on spins and polarisations. But there is another aspect to entanglement, which is the control of decoherence. When one particle decoheres, the particle it is entangled with immediately decoheres. In earlier times, entanglement referred to two particle systems, but modern research has shown that large numbers of particles can be entangled. Moreover in a system such as organic matter new particles can be brought into entanglement, entanglement can be moved to different parts of the system, and particles that have decohered can become re-entangled.
This brings us to the question of quantum coherence in organic matter. You may find on the internet or read in popular science books the claim that quanta in organic matter would decohere too rapidly to be relevant to its function. A paper by Max Tegmark (1. Tegmark, 2000) is often quoted in this respect. It is true that the conditions of organic matter lead to rapid coherence, but the argument that this prevents coherence having a role in the functioning of organic matter has now been refuted by a whole series of studies.
The first of these was a paper by Greg Engel (2. Engel et al, 2007). This showed that the coherent state of electrons in the photosynthetic complexes of bacteria allowed a much more efficient transfer of energy within these complexes than would be possible with a classical system. The efficiency of energy transfer appears to offer an adaptive advantage to organisms that evolve a coherent system. At first, it appeared possible that the Engel paper might only refer to organisms under rather extreme conditions. His paper dealt with bacteria existing at 77 Kelvin, and coherence is more difficult to maintain at higher temperatures. Since this initial paper in 2007, however, the scope of functional quantum coherence in organisms has been seen to be widespread. A paper by Elizabetta Collini in 2010 (3. Collini et al, 2010) studied functional quantum coherence in organisms at room temperature, while Calhoun et al (4. Calhoun et al, 2009) discussed coherence in multicellular plants. Furthermore, organic quantum coherence may not be confined to plants. A recent study showed that in some aphids that possessed caretenoids, a pigment found in the chloroplasts of plants, light was able to boost ATP production.
Quantum entanglement in organic matter
The other aspect is the role of quantum entanglement in these organic processes. It is clear from recent studies that entanglement exists between electrons in these organisms, but opinion is divided as to whether it has a functional role, or whether this only applies to the coherent state of electrons. What is clear, however, is that entanglement does at least have the potential to be functional in organic material.
In 2010, a study by Francesca Fassioli and Alexandra Olaya-Castro (5. Fassioli & Olaya Castro, 2010) argued that quantum entanglement may be involved in the efficiency of photosynthetic systems. They suggest that entanglement could play a role in coherence-assisted light-harvesting, by allowing precise control of the rate at which excitations are transferred to the photosynthetic reaction centre. That in a sentence is really the nub of it. It appears possible that entanglement can exercise control over coherence, which is itself functional in organic systems.
There is suggested to be a correlation between the extent of entanglement and the efficiency of energy transport. In these systems, quantum coherence is spatially distributed in such a way that entanglement between pairs of molecules allows the control of energy transport in response to variations in the environment. It is argued that a combination of entanglement and coherence may allow a photosynthetic system to cope with varying light intensities. Further to this, another study by Sarovar et al (6. Sarovar, 2009) examined the non-local correlation between the electronic states of spatially separated chromophores. In addition, Ishizaki and Fleming (7. Ishizaki & Fleming, 2009) argued that where entanglement causes decoherence at other sites in an organism, there could be a resurgence of coherence and entanglement at the distant sites, so that in a large system entanglement was not necessarily a point-to-point effect, but instead something more complex that could recycle itself around the system.
Finally a study a 2011 study has looked at the possibility of quantum entanglement in proteins (9. Guerreschi, 2009). This study discusses molecules forced out of thermal equilibrium by oscillations being able to sustain entanglement that would normally be destroyed by environmental noise. It is thought likely that conformational changes in protein may support this type of quantum entanglement. Such conformational changes can force spins to come close or move apart. When spins are far apart, with an interaction that is weaker than the surrounding field there is no entanglement. However, when the spins are forced closer together, the interaction can become stronger than the surrounding field, and entanglement can appear. The oscillation of molecules can thus allow a cyclic regeneration of entanglement. On this basis, entanglement can persistently recur on an oscillating molecule, even if the environment is too hot for static entanglement. This is seen as the basis for functional quantum entanglement in organic matter.
Conclusion
Out of this rather difficult material, we can begin to see how remote communications between organisms could function within the existing scientific paradigm. Quantum entanglement is the only property in physics that has the potential to act as the basis for such a mechanism. We have seen that entanglement has been shown to act instantaneously over any distance, and that it can control decoherence of remote quanta. This latter property now looks to be more interesting than the determination of spin, because quantum coherence has in recent years been shown to have a functional roles in organic matter, possibly including proteins at ambient temperature. On this basis, it is possible to speculate that entanglement between quanta in different organisms could lead to a change in one organism altering functional coherence in a remote one, and thus altering the experience and/or behaviour of the remote organism.
References:-
1.) Tegmark, M. (2000) – Importance of quantum coherence in brain processes – Physical Review, E 61, pp. 4194 – 4206
2.) Engel et al (2007) – Evidence for wavelike transfer through quantum coherence in photosynthetic systems – Nature, 446, p. 782
3.) Collini, Elizabetta et al (2010) – Coherently wired light-harvesting in photosynthetic marine algae at ambient temperatures – Nature, 463, pp. 644-7, doi:10.1038/nature 08811
4.) Calhoun, T.R. (2009) – Journal of Physical Chemistry, B., 113, 16291
5.) Fassioli, Francesca & Olaya-Castro, Alexandra (2010) – Distribution of entanglement in light-harvesting complexes and their quantum efficiency – arXiv: 1012.4059vl [quant-ph]
6.) Sarovar M. et al (2009) – Quantum entanglement in photosynthetic light-harvesting complexes
7.) Ishizaki, A. & Fleming, G. (2009) – Theoretical examination of quantum coherence in photosynthetic systems at physiological temperature – PNAS, 7 August 2009
8.) Guerreschi, G., Cai, J., Popescu, S. & Briegel, H. – Persistent dynamic entanglement from classical motion: How biomolecular machines can generate non-trivial quantum states – arXiv; 1111.2126vl [quant-ph] 9 November 2011
