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Quantum entanglement in photosynthesis?

Nanotechnology is, ultimately, a mechanization of the molecular processes of life. One of the most important of those processes is photosynthesis. If we really understood photosynthesis as deeply as we do, say, gear trains, and had the machinery to build whatever molecular machines we designed, we could build trees that produced gasoline from sunlight and the CO2 in the air.

(just for fun: a gasoline tree with an effective area of 100 m2 would produce about 3 gallons per hour of direct sunlight.)

Quantum entanglement is primarily a laboratory curiosity at the macroscopic scale (at the atomic scale nothing works without quantum mechanics, of course). The major uses that anyone is working on are quantum computing and cryptography. It’s generally thought that quantum effects vanish in systems as large and warm as living cells.

Now a paper from a group at Berkeley claims that quantum entanglement seems to be occurring in photosynthesis:

Light harvesting components of photosynthetic organisms are complex, coupled, many-body quantum systems, in which electronic coherence has recently been shown to survive for relatively long time scales despite the decohering effects of their environments. Within this context, we critically analyze entanglement in multi-chromophoric light harvesting complexes; we clarify the connection between coherence and entanglement in these systems, and establish methods for quantification of entanglement by presenting necessary and sufficient conditions for entanglement and by deriving a measure of global entanglement. These methods are then applied to the Fenna-Matthews-Olson (FMO) protein to extract the initial state and temperature dependencies of entanglement in this complex. We show that while FMO in natural conditions largely contains bipartite entanglement between dimerized chromophores, a small amount of long-range and multipartite entanglement exists even at physiological temperatures. This constitutes the first rigorous quantification of entanglement in a biological system. Finally, we discuss the practical utilization of entanglement in densely packed molecular aggregates such as light harvesting complexes.

The observed entanglement only lasts for picosecond timescales, but that’s enough to affect a chemical reaction.

From later in the paper (LHC = Light Harvesting Complex):

… while entanglement in these systems is a by-product of this quantum coherence – since as discussed in this work, in the presence of coherence entanglement naturally exists for states in the single excitation subspace – it is however not clear whether it has a significant role in the functioning of light harvesting complexes. The non-local correlations of chromophoric electronic states that entanglement embodies are unlikely to impact excitation transport, the main function of LHCs. It is more plausible that entanglement exists merely as a consequence of the critical electronic coherence and the resulting excitation delocalization.
Even if it does not play a significant role in the light harvesting functioning of LHCs, the existence of entanglement in these systems has important practical implications due to the technological applications of entangled states. For example, the presence of entanglement in LHCs sets the stage for investigating the applicability of entanglement-enhanced precision measurement [41] in biological systems. …
In addition to precision metrology, densely packed molecular aggregates such as LHCs have potential for constructing naturally robust quantum devices. …

(H/T Technology Review)

4 Responses to “Quantum entanglement in photosynthesis?”

  1. Says:

    Thanks to Berkeley for the first paper on quantum entangelment in LCH’s. Fascinating. Live long and prosper.
    Mark J. Fiore
    markfiore50@hotmail.com

  2. Marco Sacilotti Says:

    to Foresight Institute &
    to Mohan Sarovar

    I have seen your work on FMO (photosynthesis and entanglement). Congratulations!
    I do not work on entanglement but, may be the enclosed information can be interesting to you (and, may be, for an interesting discussion).
    I’m a physicist working on semiconductors and bandgap engineering for many years.
    Few years ago I could observe that the photosynthesis mechanism, for the electrical charges separation, could be explained by type II (staggered) energetic interfaces between two different molecules.
    More, I’d found that Forster’s theory, for photosynthesis, violates physical laws. This for 3 reason described enclosed (please, see enclosed the ppt in total screen motion). May be this is the only energetic configuration able to separate electrical charges under attraction.
    For this reason I’d prepare a paper, published in Nasa-Arxiv about photosynthesis: http://arxiv.org/abs/1005.1337

    In your FMO-entanglement work, what bothers me is the fact that molecules are separated from their natural environement. Changing the environement, you change the band-gap relative position. This does not imply that your results are not correct but I’m wondering if you can correlate it with the photosynthesis mechanism.
    Moreover, a recent work by Yen Hsun Su et al (Nanoscale vol. 2, page 2639 2010, enclosed) show that changing the medium (environement) in which molecules are present, you change the colour of the leaves. This means that the grenn colour of plants is not a reflexion. If the Chl molecules are still there, it means that the green color of plants can be an emission (interface emission, like in the ppt motion enclosed).

    The ppt enclosed is, may be, the only energetic configuration able to separate electrical charges (able to produce an interface electric field, by energy band bending). You have a paper enclosed (OSA-LAOP publication) showing the interface electric field, necessary to separate electrical charges.

    Could you please comment about the FMO results you have (changing the molecules medium) and entanglement? Should we relate it to photosynthesis? Or relate it to a new observation of interaction between organic molecules?

    Thank you

    Marco Sacilotti
    professeur émérite – Université de Bourgogne France
    visitting professor – Depto Fisica UFPE Recife Brazil
    msacilot@gmail.com

    PS
    Recently Yen Hsun Su et al (Nanoscale vol. 2, page 2639 2010), doping sea-urchins with gold nanoparticles, showed that is possible to change the leaves’ colour to red, yellow or blue, depending on the excitation light and the gold nanoparticle size. Exciting sea-urchins/gold system with white light they could obtain yellow colored leaves. Exciting the sea-urchins/gold system with UV (285 nm) they could obtain blue and red colored leaves. As the Chl-a is still there (in the sea-urchins leaf), if green is a reflexion, due to Chl-a, the sea-urchins should keep green. It means we cannot take Chl-a from leaves and conclude “plants are green because Chl-a do not absorbs green light”. Gold nanoparticles change the Chl-a environment, changing the emission colour, and the Chl-a is still there. If they are still there and we cannot consider reflexion anymore, what should be the Gold/Chl-a red or blue mechanism: emission or reflexion ?
    More, an ancient paper by Steven Boxer from Standford University (Mita Chattoraj et al, Proc. Natl. Acad. Sci. USA, vol. 93, p. 8362 August 1996, Biophysics), by exciting GFP, it was proposed tthat the two visible absorption bands correspond to two ground-state conformations. The staggered band gap relative position has “two ground-state like” conformations (please see enclosed the work by Boxer group).

  3. Marco Sacilotti Says:

    Dear Mohan Sarovar

    I have seen your work on FMO (photosynthesis and entanglement). Congratulations!
    I do not work on entanglement but, may be the enclosed information can be interesting to you (and, may be, for an interesting discussion).
    I’m a physicist working on semiconductors and bandgap engineering for many years.
    Few years ago I could observe that the photosynthesis mechanism, for the electrical charges separation, could be explained by type II (staggered) energetic interfaces between two different molecules.
    More, I’d found that Forster’s theory, for photosynthesis, violates physical laws. This for 3 reason described enclosed (please, see enclosed the ppt in total screen motion). May be this is the only energetic configuration able to separate electrical charges under attraction.
    For this reason I’d prepare a paper, published in Nasa-Arxiv about photosynthesis: http://arxiv.org/abs/1005.1337

    In your FMO-entanglement work, what bothers me is the fact that molecules are separated from their natural environement. Changing the environement, you change the band-gap relative position. This does not imply that your results are not correct but I’m wondering if you can correlate it with the photosynthesis mechanism.
    Moreover, a recent work by Yen Hsun Su et al (Nanoscale vol. 2, page 2639 2010, enclosed) show that changing the medium (environement) in which molecules are present, you change the colour of the leaves. This means that the grenn colour of plants is not a reflexion. If the Chl molecules are still there, it means that the green color of plants can be an emission (interface emission, like in the ppt motion enclosed).

    The ppt enclosed is, may be, the only energetic configuration able to separate electrical charges (able to produce an interface electric field, by energy band bending). You have a paper enclosed (OSA-LAOP publication) showing the interface electric field, necessary to separate electrical charges.

    Could you please comment about the FMO results you have (changing the molecules medium) and entanglement? Should we relate it to photosynthesis? Or relate it to a new observation of interaction between organic molecules?

    Thank you

    Marco Sacilotti
    professeur émérite – Université de Bourgogne France
    visitting professor – Depto Fisica UFPE Recife Brazil
    msacilot@gmail.com

    PS
    Recently Yen Hsun Su et al (Nanoscale vol. 2, page 2639 2010), doping sea-urchins with gold nanoparticles, showed that is possible to change the leaves’ colour to red, yellow or blue, depending on the excitation light and the gold nanoparticle size. Exciting sea-urchins/gold system with white light they could obtain yellow colored leaves. Exciting the sea-urchins/gold system with UV (285 nm) they could obtain blue and red colored leaves. As the Chl-a is still there (in the sea-urchins leaf), if green is a reflexion, due to Chl-a, the sea-urchins should keep green. It means we cannot take Chl-a from leaves and conclude “plants are green because Chl-a do not absorbs green light”. Gold nanoparticles change the Chl-a environment, changing the emission colour, and the Chl-a is still there. If they are still there and we cannot consider reflexion anymore, what should be the Gold/Chl-a red or blue mechanism: emission or reflexion ?
    More, an ancient paper by Steven Boxer from Standford University (Mita Chattoraj et al, Proc. Natl. Acad. Sci. USA, vol. 93, p. 8362 August 1996, Biophysics), by exciting GFP, it was proposed tthat the two visible absorption bands correspond to two ground-state conformations. The staggered band gap relative position has “two ground-state like” conformations (please see enclosed the work by Boxer group).

  4. Marco Sacilotti Says:

    OK

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