The attitude towards the quantum vision about living systems depend on the basic prejudices of the scientist. Average hard wired guy willing to appear as an authority relies on text book wisdom and of course immediately tells that quantum effects cannot be significant in length and time scales involved and that there is absolutely no evidence for them. We should not however trust text book wisdom and -as I have learned- even less to average physicists;-)! After all, living systems look very quantal and we experience directly what could be called free will. We should rely on what we directly experience and ability to think rationally rather than authorities and be ready to question also the existing view about quantum physics.
What could biology and neuroscience give to the quantum physics? This should be the question. If the standard quantum physics does not allow the needed macroscopic quantum phases, we must modify the quantum physics. Even quantum consciousness theorists have usually adopted the view that wave mechanics is enough for understanding of living matter. Penrose has been an exception since he proposes that quantum gravity could be important. Perhaps it is not a mere co-incidence that persons who most passionately believe that the old theory is enough, have also the most limited skills as theorists.
During years I have learned that there is a lot of indirect experimental evidence for the quantum view (the strange findings about the functioning of cell membrane, the effects of ELF em fields on vertebrate brain,...), and have used these bits of experimental data to develop TGD based view about quantum physics. This involves the identification of dark energy and dark matter in terms of macroscopic quantum phases with non-standard large value of Planck constant, the new view about space-time and about the relationship between experienced time and time of physicists, new view about quantum states based on zero energy ontology, etc.. Also p-adic physics is essential in the proposed view about correlates of cognition and intention. Of course, this all this is very speculative and my frustrating realization has been that the good theory necessarily comes long before the experiments directly testing it.
During years the experimentation to test the presence of quantum effects in living matter has begun. And the positive evidence is accumulating. In Discover magazine there is an article titled Is Quantum Mechanics Controlling Your Thoughts? telling among other things about the latest direct evidence of quantum effects provided by experiments related to photosynthesis and odor perception.
Quantum coherence and photosynthesis
The article summarizes in popular terms the contents of the paper Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems by Fleming and collaborators reporting evidence for quantum coherence in photosynthesis. The absorption of photon induces electron current from the point of capture- chlorosome- to the reaction centers. The semiclassical theory predicts the dissipation of the electronic energy to be about 20 per cent whereas the observed dissipation is only about 5 per cent. This suggests quantum coherence. The following abstract of the original article summarizes the essentials.
Photosynthetic complexes are exquisitely tuned to capture solar light efficiently, and then transmit the excitation energy to reaction centres, where long term energy storage is initiated. The energy transfer mechanism is often described by semiclassical models that invoke 'hopping' of excited-state populations along discrete energy levels. Two-dimensional Fourier transform electronic spectroscopy has mapped6 these energy levels and their coupling in the Fenna–Matthews–Olson (FMO) bacteriochlorophyll complex, which is found in green sulphur bacteria and acts as an energy 'wire' connecting a large peripheral light-harvesting antenna, the chlorosome, to the reaction centre. The spectroscopic data clearly document the dependence of the dominant energy transport pathways on the spatial properties of the excited-state wavefunctions of the whole bacteriochlorophyll complex. But the intricate dynamics of quantum coherence, which has no classical analogue, was largely neglected in the analyses—even though electronic energy transfer involving oscillatory populations of donors and acceptors was first discussed more than 70 years ago11, and electronic quantum beats arising from quantum coherence in photosynthetic complexes have been predicted and indirectly observed. Here we extend previous two-dimensional electronic spectroscopy investigations of the FMO bacteriochlorophyll complex, and obtain direct evidence for remarkably long-lived electronic quantum coherence playing an important part in energy transfer processes within this system. The quantum coherence manifests itself in characteristic, directly observable quantum beating signals among the excitons within the Chlorobium tepidum FMO complex at 77 K. This wavelike characteristic of the energy transfer within the photosynthetic complex can explain its extreme efficiency, in that it allows the complexes to sample vast areas of phase space to find the most efficient path.
The popular article translates the article to the following piece of text.
To unearth the bacteria’s inner workings, the researchers zapped the connective proteins with multiple ultra-fast laser pulses. Over a span of femtoseconds, they followed the light energy through the scaffolding to the cellular reaction centers where energy conversion takes place. Then came the revelation: Instead of haphazardly moving from one connective channel to the next, as might be seen in classical physics, energy traveled in several directions at the same time. The researchers theorized that only when the energy had reached the end of the series of connections could an efficient pathway retroactively be found. At that point, the quantum process collapsed, and the electrons’ energy followed that single, most effective path.
My own interpretation would be following.
- Remarkably long lived electronic quantum coherence is claimed to be present. Authors propose that quantum computation like process - quantum random walk -could be in question. If I have understood correctly, the proposed process can halt only by a state function reduction localizing the electron at the reaction center. Completely standard Schrödinger evolution in the network would be otherwise in question. The good news is that the average time to find from the entrance to exit in this kind of process is exponentially shorter than in the classical random walk. One can say that exit plus all other points are always reached after some minimum time and it is enough to perform the state function reduction localizing the electron to the exit.
- Somewhat confusingly, the popularizers claim that the authors argue (I do not have access to the original article) that the quantum random walk selects the shortest path from the chlorosome to the reaction center is in question. Quantum collapse is a non-deterministic process and if it selects the path in this particular case it can select any path with some probability, not always the shortest one. The selection of the shortest path is not necessarily needed since the quantum random walk with fixed entrance and exit is by its inherent nature exponentially faster than its classical counterpart. The proposed interpretation makes sense only if the state function reduction takes place immediately after the electron's state function at the exit becomes non-vanishing. Does it? I cannot say.
If one accepts this view, the sole problem is to understand how macroscopic quantum coherence is possible in the length scales considered. There are good arguments supporting the view that this is not the case for the ordinary quantum mechanics. In TGD framework the hierarchy of Planck constants suggests that both macroscopic quantum coherence and very low dissipation rate are due to the large value of hbar for electrons. For instance, for hbar=5×hbar0 the naive estimate is that dissipation rate should reduce by a factor 1/5 and coherence times and lengths should increase by a factor 5. I have proposed much larger values of hbar in the model of living system. In particular, the model for high temperature super-conductivity assigns to these systems basic biological length scales from p-adic length scale hypothesis (5 nm thickness of lipid layer of cell membrane corresponds to L(149), 10 nm thickness of lipid layer to L(151) and the length scale 2.5 μm of cell nucleus to L(167)). The electron Compton length is scaled up by a factor 211 to so that it corresponds to the p-adic length scale L(149)=5 nm. This would scale up the fundamental bio-time scale of .1 seconds predicted by TGD to be the time scale assignable to causal diamond of electron by factor 222 to about 4 × 105 seconds.
For TGD based ideas about photosynthesis see this.
Odor perception and quantum coherence
The article discusses also the work of the biophysicist Luca Turin related to odor perception as additional support for quantum brain. Before going to the article it is good to summarize the basic ideas about sensory qualia (colors, odors, ...) in TGD inspired theory of consciousness.
- In TGD framework the identification of qualia follows from the identification of quantum jump as a moment of consciousness. Just as quantum numbers characterize the physical state, the increments of quantum numbers characterize the quantum jump between two states. This leads to a capacitor model of the sensory receptor in which the sensory perception corresponds to a generalized di-electric breakdown in which various particles carrying some quantum numbers flow between electrodes and the change of the quantum numbers at second electrodes gives rise to the sensory quale in question.
- It is important that sensory qualia are assigned to the sensory receptors rather than to the neural circuitry of brain as in standard neuroscience. This leads to objections (phantom leg for instance) which are circumvented in TGD based vision about 4-D brain. For instance, phantom leg would correspond to sensory memory resulting by sharing the mental image about pain residing in the geometric past when the leg still existed. A massive back-projection generating virtual sensory input from brain (or from the magnetic body via brain) is needed to build the actual perception as a kind of art-work by filtrating from the actual sensory input a lot of unessential stuff and amplifying the essential features.
- The discovery of Callahan that odor perception of insects seems to be based on IR light inspired my own the proposal that photons at IR frequencies could be involved with the odor perception so that odor perception would be at molecular level seeing by IR light. Even hearing could involve similar "seeing" in appropriate frequency range. Massless extremals (topological light rays) would serve as kind of wave guides parallel to axons along which light would propagate as kind of laser beams between receptor and brain. This would also explain why the mediation of auditory input takes so rapidly.
- I have also proposed frequency coding for the sensory qualia. The first proposal which I dubbed as "Spectroscopy of Consciousness" stated that cyclotron frequencies assignable to various biologically important ions -much below IR range- associated with as such correspond to sensory qualia. Later I gave up this idea and proposed that frequencies code provide only a symbolic representations- define their names- as one might say. The information about qualia and more general sensory data would be represented in terms of cyclotron frequencies inducing dynamical patterns of the cyclotron Bose-Einstein condensates of biologically important ions residing at the magnetic body receiving the sensory information.
Quantum physics may explain the mysterious biological process of smell, too, says biophysicist Luca Turin, who first published his controversial hypothesis in 1996 while teaching at University College London. Then, as now, the prevailing notion was that the sensation of different smells is triggered when molecules called odorants fit into receptors in our nostrils like three-dimensional puzzle pieces snapping into place. The glitch here, for Turin, was that molecules with similar shapes do not necessarily smell anything like one another. Pinanethiol [C10H18S] has a strong grapefruit odor, for instance, while its near-twin pinanol [C10H18O] smells of pine needles. Smell must be triggered, he concluded, by some criteria other than an odorant’s shape alone.
What is really happening, Turin posited, is that the approximately 350 types of human smell receptors perform an act of quantum tunneling when a new odorant enters the nostril and reaches the olfactory nerve. After the odorant attaches to one of the nerve’s receptors, electrons from that receptor tunnel through the odorant, jiggling it back and forth. In this view, the odorant’s unique pattern of vibration is what makes a rose smell rosy and a wet dog smell wet-doggy.
The article A spectroscopic mechanism for primary olfactory perception by Turin explains in detail his theory and various experimental tests. Here are the core ideas in more quantitative terms.
- The theory originates from the proposal of Dyson (not that Dyson;-)!) proposed already 1938 that odor perception might rely on the vibrational spectrum of the odorant rather than its shape alone. The spectrum would be in the wave length range 2.5-10 μm corresponding to photon energies in the range .5 eV - .125 eV. This vibrational spectrum would be excited by the current of electrons tunneling from the receptor to the odorant molecule.
- The proposal is that odor receptor can be regarded as a pair formed by a source and sink of electrons. If there is nothing between source and sink, tunneling can occur if there is electronic energy state with same energy in both source and sink. If there is an odorant molecule between source and sink with vibrational energy E, tunneling can occur indirectly: the electron can excite a vibrational state with this energy and tunneling can occur only if the difference of electron energies in source and sink is E. Therefore the presence of odor molecule would be detected from the occurrence of the tunneling and vibrational energy spectrum would characterize the odor molecule.
One can compare the model of Turin with TGD based ideas.
- The theory of Turin conforms at the general level with the receptor model. The "electrodes" of the sensory capacitor would correspond to the source and sink of electrons and the presence of the odorant molecule between the "electrodes" would induce the current. The current of electrons from the source to the sink should induce the change of total quantum numbers defining the odor quale.
- The first thing to notice is that the upper bound .5 eV for IR energies corresponds to the nominal value of the metabolic energy quantum identified as the energy liberated as proton drops from the atomic space-time sheet with k=137 to a very large space-time sheet or the same process for electron Cooper at k=149 space-time sheet. If Cooper pairs are involved, the latter process would occur in the length scale defined by the thickness of the lipid layer of the cell membrane (5 nm). The lower bound corresponds to a metabolic energy quantum assignable to k= 139 for protons and k=151 transition for electrons (thickness of cell membrane).
- Second point to notice is that TGD predicts a fractal hierarchy of spectra of metabolic energy quanta coming as E(Δk,n)= 2-ΔkE0(1-2-n), n=1,2,..., converging to E(Δk,∞)= 2-ΔkE0 for given p-adic length scale characterized by the difference Δk=k-k0 . E0 denotes the zero point kinetic energy of particle at space-time sheet with p-adic length scale k=k0 and is inversely proportional to the mass of the particle. The transfer of electrons and/or protons between different space-time sheets with any perception for purely metabolic reasons. The simplest option is that since the electrons at the side of the source receive their energy in this manner, their energy spectrum is given by E(Δk,n) (there is of course some resolution meaning a cutoff in n). The specificity of the receptor would require preference of some specific metabolic energy quanta E(Δk,n). If this spectrum characterizes the receptor independently of its chemistry, then not only metabolic energy quanta but also the mechanism of sensory perception is universal. This proposal fails if the receptor has always same spectrum of E(Δk,n) since all receptors would detect all odors.
It is interesting to relate the theory of Turin with the hypothesis of Callahan that the odor perception of insects uses IR light.
- Callahan's work (Callahan, P. S. (1977). Moth and Candle: the Candle Flame as a Sexual Mimic of the Coded Infrared Wavelengths from a Moth Sex Scent. Applied Optics. 16(12) 3089-3097) suggests that the IR photons emitted by the odorant in the transitions between the vibrational states and received by the odor receptor are basically responsible for the odor perception. Turin in turn proposes that the pattern of vibrational excitations in the odor molecule characterizes the perception. These views are consistent if the pattern of vibrational excitations is in 1-1 correspondence with the flow pattern of electrons between different space-time sheets at the receptors if a kind of self-organization pattern results: this is expected to take place in presence of a metabolic energy feed.
- In Callahan's model for the odor perception of insects the simplest odor receptor would "see" the IR light emitted by the odor molecules. Also Turin explains -with different assumptions- that the situation is analogous to that prevailing in retina in that there are receptors sensitive to characteristic energy ranges of photons. One would expect that the odor perception of insects is something very simple. The so called vomeronasal organ is known to be responsible for the perception of socially important odors not generating conscious experience at our level of self hierarchy but having important effect on behavior (perfume industry has long ago realized this!). Vomeronasal organ could utilize this kind of primitive odor receptors.
- The rate for the spontaneous transitions emitting IR light could be rather low. A more advanced receptor would induce more transitions by using tunneling electrons to excite vibrational energy levels in the odorant. This would be like using lamp to see better! The analogy with the transistor is also suggestive: the small base current induced by IR radiation generated by the odor molecule would be amplified in the process. Since the source contains electrons in excited states (at smaller space-time sheets), odor molecules could send negative energy photons dropping electrons to the large space-time sheet along which tunneling is possible. Induced emission would cause a domino like flow of electrons and excitations of the vibrational states of the odor molecule as the counterpart of di-electric breakdown would take place.
- What could then the physical correlates for the primary odor qualia? The increments of some quantum numbers assignable to electrons at the source should be in question. Could the energies E(k,n) characterizing the receptor define the primary odors? Odors and tastes are indeed very intimately related to metabolic activities;-). A natural consequence would be that besides the radiation generated by the transfer of electrons between space-time sheets would induce odor and perhaps also taste sensation. Organisms serve as food for other organisms so that an optimal detection of nutrients would be the outcome.
Could one assume that also other receptors use metabolic energy quanta as basic excitation energies?
- The first objection is that similar "metabolic qualia" would result in all receptors. This is not a problem if these qualia are qualia not conscious to us but conscious to neuronal selves. For instance, in the TGD based model for visual colors the increments of color quantum numbers (in QCD sense!) define the basic colors, which means that colored particles must be in question (TGD variant of quark color implies the existence of scaled variants of QCD like physics and predicts that also electrons have colored excitations for which there is indeed a growing experimental evidence).
- Second objection is that it does not seem possible to identify E(k,n) as excitation energies in the case of vision. The relevant range of photon energies is [1.65,3.3] eV. By scaling the metabolic energy quantum by a power of 2, the nominal values of relevant maximal metabolic energy quanta E(k,n=∞) are 2 eV and 4 eV. The series of energies approaching 2 eV below 2 eV is 1, 1.5, 1.75, ..., 2 eV so that the range below 2 eV representing red light would be covered. Above 2 eV the series is 2, 3, 3.50,...,4 eV so that the region above 2 eV (orange, yellow, green, blue, indigo, violet) would contain only single line at 3 eV (violet). If the incoming photon can kick the electron to an excited state with energy E0 at the smaller space-time sheet the spectrum contains also the energies E(k,n)+E0. For E0=1.3 eV these excitation energies would come as 2.3, 2.8, 3.05,... 3.3 eV and cover this range.
For TGD based view about qualia see the chapter Quantum Model for Qualia of the book "Bio-systems as Conscious Holograms".