efficient chlorophyll quantum photosynthesis, Mohan Sarovar UCB: Rich Murray 2010.09.03

[Rich Murray]

efficient chlorophyll quantum photosynthesis, Mohan Sarovar UCB: Rich Murray
2010.09.03


http://www.scientificamerican.com/article.cfm?id=quantum-entanglement-and-photo

As nature's own solar cells, plants convert sunlight into energy via
photosynthesis. New details are emerging about how the process is able to
exploit the strange behavior of quantum systems, which could lead to
entirely novel approaches to capturing usable light from the sun.

All photosynthetic organisms use protein-based "antennas" in their cells to
capture incoming light, convert it to energy and direct that energy to
reaction centers -- critical trigger molecules that release electrons and
get the chemical conversion rolling. These antennas must strike a difficult
balance: they must be broad enough to absorb as much sunlight as possible
yet not grow so large that they impair their own ability to shuttle the
energy on to the reaction centers.

This is where quantum mechanics becomes useful. Quantum systems can exist in
a superposition, or mixture, of many different states at once. What's more,
these states can interfere with one another -- adding constructively at some
points, subtracting at others. If the energy going into the antennas could
be broken into an elaborate superposition and made to interfere
constructively with itself, it could be transported to the reaction center
with nearly 100 percent efficiency.

A new study by Mohan Sarovar, a chemist at the University of California,
Berkeley, shows that some antennas -- namely, those found on a certain type
of green photosynthetic bacteria -- do just that. Moreover, nearby antennas
split incoming energy between them, which leads not just to mixed states but
to states that are entangled over a broad (in quantum terms) distance.
Gregory Scholes, a chemist at the University of Toronto, shows in a soon to
be published study that a species of marine algae utilizes a similar trick.
Interestingly, the fuzzy quantum states in these systems are relatively
long-lived, even though they exist at room temperature and in complicated
biological systems. In quantum experiments in the physics lab, the slightest
intrusion will destroy a quantum superposition (or state).

These studies mark the first evidence of biological organisms that exploit
strange quantum behaviors. A better understanding of this intersection of
microbiology and quantum information, researchers say, could lead to
"bioquantum" solar cells that are more efficient than today's photovoltaics.

Note: This article was originally printed with the title, "Chlorophyll
Power."

http://newscenter.lbl.gov/feature-stories/2010/05/10/untangling-quantum-entanglement/

Untangling the Quantum Entanglement Behind Photosynthesis: Berkeley
scientists shine new light on green plant secrets

MAY 10, 2010
Lynn Yarris [phone]  [hidden email]
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Mohan Sarovar (seated) and (from left) Akihito Ishizaki, Birgitta Whaley and
Graham Fleming carried out the first observation and characterization of
quantum entanglement in a real biological system. (Photo by Roy Kaltschmidt,
Berkeley Lab Public Affairs)

The future of clean green solar power may well hinge on scientists being
able to unravel the mysteries of photosynthesis, the process by which green
plants convert sunlight into electrochemical energy. To this end,
researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley
National Laboratory (Berkeley Lab) and the University of California (UC),
Berkeley have recorded  the first observation and characterization of a
critical physical phenomenon behind photosynthesis known as quantum
entanglement.

Previous experiments led by Graham Fleming, a physical chemist holding joint
appointments with Berkeley Lab and UC Berkeley, pointed to quantum
mechanical effects as the key to the ability of green plants, through
photosynthesis, to almost instantaneously transfer solar energy from
molecules in light harvesting complexes to molecules in electrochemical
reaction centers. Now a new collaborative team that includes Fleming have
identified entanglement as a natural feature of these quantum effects. When
two quantum-sized particles, for example a pair of electrons, are
"entangled," any change to one will be instantly reflected in the other, no
matter how far apart they might be. Though physically separated, the two
particles act as a single entity.


The schematic on the left shows the absorption of light by a light
harvesting complex and the transport of the resulting excitation energy to
the reaction center through the FMO protein. On the right is a monomer of
the FMO protein, showing its orientation relative to the antenna and the
reaction center. The numbers label FMO's seven pigment molecules. (Image
from Mohan Sarovar)

"This is the first study to show that entanglement, perhaps the most
distinctive property of quantum mechanical systems, is present across an
entire light harvesting complex," says Mohan Sarovar, a post-doctoral
researcher under UC Berkeley chemistry professor Birgitta Whaley at the
Berkeley Center for Quantum Information and Computation. "While there have
been prior investigations of entanglement in toy systems that were motivated
by biology, this is the first instance in which entanglement has been
examined and quantified in a real biological system."

The results of this study hold implications not only for the development of
artificial photosynthesis systems as a renewable non-polluting source of
electrical energy, but also for the future development of quantum-based
technologies in areas such as computing -- a quantum computer could perform
certain operations thousands of times faster than any conventional computer.

"The lessons we're learning about the quantum aspects of light harvesting in
natural systems can be applied to the design of artificial photosynthetic
systems that are even better," Sarovar says. "The organic structures in
light harvesting complexes and their synthetic mimics could  also serve as
useful components of quantum computers or other quantum-enhanced devices,
such as wires for the transfer of information."

What may prove to be this study's most significant revelation is that
contrary to the popular scientific notion that entanglement is a fragile and
exotic property, difficult to engineer and maintain, the Berkeley
researchers have demonstrated that entanglement can exist and persist in the
chaotic chemical complexity of a biological system.

"We present strong evidence for quantum entanglement in noisy
non-equilibrium systems at high temperatures by determining the timescales
and temperatures for which entanglement is observable in a protein structure
that is central to photosynthesis in certain bacteria," Sarovar says.

Sarovar is a co-author with Fleming and Whaley of a paper describing this
research that appears on-line in the journal Nature Physics titled "Quantum
entanglement in photosynthetic light-harvesting complexes." Also
co-authoring this paper was Akihito Ishizaki in Fleming's research group.

Green plants and certain bacteria are able to transfer the energy harvested
from sunlight through a network of light harvesting pigment-protein
complexes and into reaction centers with nearly 100-percent efficiency.
Speed is the key -- the transfer of the solar energy takes place so fast
that little energy is wasted as heat. In 2007, Fleming and his research
group reported the first direct evidence that this essentially instantaneous
energy transfer was made possible by a remarkably long-lived, wavelike
electronic quantum coherence.


Through photosynthesis, green plants are able to capture energy from
sunlight and convert it into chemical energy. By exploiting quantum
mechanical effects, the plants transfer energy from sunlight with an
efficiency of nearly 100-percent.

Using electronic spectroscopy measurements made on a femtosecond (millionths
of a billionth of a second) time-scale, Fleming and his group discovered the
existence of "quantum beating" signals, coherent electronic oscillations in
both donor and acceptor molecules. These oscillations are generated by the
excitation energy from captured solar photons, like the waves formed when
stones are tossed into a pond. The wavelike quality of the oscillations
enables them to simultaneously sample all the potential energy transfer
pathways in the photosynthetic system and choose the most efficient.
Subsequent studies by Fleming and his group identified a closely packed
pigment-protein complex in the light harvesting portion of the
photosynthetic system as the source of coherent oscillations.

"Our results suggested that correlated protein environments surrounding
pigment molecules (such as chlorophyll) preserve quantum coherence in
photosynthetic complexes, allowing the excitation energy to move coherently
in space, which in turn enables highly efficient energy harvesting and
trapping in photosynthesis," Fleming says.

In this new study, a reliable model of light harvesting dynamics developed
by Ishizaki and Fleming was combined with the quantum information research
of Whaley and Sarovar to show that quantum entanglement emerges as the
quantum coherence in photosynthesis systems evolves. The focus of their
study was the Fenna-Matthews-Olson (FMO) photosynthetic light-harvesting
protein, a molecular complex found in green sulfur bacteria that is
considered a model system for studying photosynthetic energy transfer
because it consists of only seven pigment molecules whose chemistry has been
well characterized.

"We found numerical evidence for the existence of entanglement in the FMO
complex that persisted over picosecond timescales, essentially until the
excitation energy was trapped by the reaction center," Sarovar says.

"This is remarkable in a biological or disordered system at physiological
temperatures, and illustrates that non-equilibrium multipartite entanglement
can exist for relatively long times, even in highly decoherent
 environments."

The research team also found that entanglement persisted across distances of
about 30 angstroms (one angstrom is the diameter of a hydrogen atom), but
this length-scale was viewed as a product of the relatively small size of
the FMO complex, rather than a limitation of the effect itself.

"We expect that long-lived, non-equilibrium entanglement will also be
present in larger light harvesting antenna complexes, such as LH1 and LH2,
and that in such larger light harvesting complexes it may also be possible
to create and support multiple excitations in order to access a richer
variety of entangled states," says Sarovar.

The research team was surprised to see that significant entanglement
persisted between molecules in the light harvesting complex that were not
strongly coupled (connected) through their electronic and vibrational
states. They were also surprised to see how little impact temperature had on
the degree of entanglement.

"In the field of quantum information, temperature is usually considered very
deleterious to quantum properties such as entanglement," Sarovar says. "But
in systems such as light harvesting complexes, we see that entanglement can
be relatively immune to the effects of increased temperature."

This research was supported in part by U.S. Department of Energy's Office of
Science, and in part by a grant from the Defense Advanced Research Projects
Agency (DARPA).

Berkeley Lab is a U.S. Department of Energy national laboratory located in
Berkeley, California. It conducts unclassified scientific research and is
managed by the University of California. Visit our website at
http://www.lbl.gov.

Additional Information

For more information on the research of Graham Fleming, visit his Website at
www.cchem.berkeley.edu/grfgrp/

For information on the research of Birgitta Whaley visit her Website at
www.cchem.berkeley.edu/kbwgrp/

For more information on the research of Mohan Sarovar visit his Website at
www.cchem.berkeley.edu/kbwgrp/mohan/Site/Welcome.html

TAGS: clean energy, energy, solar energy


http://www.nature.com/nphys/journal/v6/n6/abs/nphys1652.html

Article abstract
Nature Physics 6, 462 - 467 (2010)
Published online: 25 April 2010 | doi:10.1038/nphys1652

Subject Categories: Quantum physics | Biological physics

Quantum entanglement in photosynthetic light-harvesting complexes
Mohan Sarovar 1,2,
Akihito Ishizaki 2,3,
Graham R. Fleming 2,3
& K. Birgitta Whaley 1,2

Abstract

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 timescales, despite the
decohering effects of their environments.
Here, we analyse entanglement in multichromophoric light-harvesting
complexes, and establish methods for quantification of entanglement by
describing necessary and sufficient conditions for entanglement and by
deriving a measure of global entanglement.
These methods are then applied to the Fenna-Matthews-Olson protein to
extract the initial state and temperature dependencies of entanglement.
We show that, although the Fenna-Matthews-Olson protein in natural
conditions largely contains bipartite entanglement between dimerized
chromophores, a small amount of long-range and multipartite entanglement
should exist even at physiological temperatures.
 This constitutes the first rigorous quantification of entanglement in a
biological system.
 Finally, we discuss the practical use of entanglement in densely packed
molecular aggregates such as light-harvesting complexes.

1 Berkeley Center for Quantum Information and Computation, Berkeley,
California 94720, USA
2 Department of Chemistry, University of California, Berkeley, California
94720, USA
3 Physical Bioscience Division, Lawrence Berkeley National Laboratory,
Berkeley, California 94720, USA
Correspondence to: Mohan Sarovar 1,2 e-mail: [hidden email]
_______________________________________________


I ran up my white flag too soon -- 23 experts firmly show YDB era Greenland
ice layer that has unique huge numbers of impact nanodiamonds in 11-page
paper in J Glaciology: Rich Murray 2010.09.02
http://rmforall.blogspot.com/2010_09_01_archive.htm
Thursday, September 2, 2010
[ at end of each long page, click on Older Posts ]
http://groups.yahoo.com/group/astrodeep/message/66
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Cox crisply comments; full text of "No evidence"; Comet theory carbonized,
Rex Dalton, nature.com; fungus found abstract: Rich Murray 2010.08.31
http://rmforall.blogspot.com/2010_08_01_archive.htm
Tuesday, August 31, 2010
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http://groups.yahoo.com/group/astrodeep/message/65
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3 times more downward energy from directed force of meteor airburst
in 3D simulations by Mark B. E. Boslough, Sandia Lab 2007.12.17:
Rich Murray 2010.08.30
http://rmforall.blogspot.com/2010_08_01_archive.htm
Monday, August 30, 2010
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http://groups.yahoo.com/group/astrodeep/message/63
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excellent Google Earth and ground views of shallow oval craters worldwide,
Pierson Barretto: Rich Murray 2010.08.22
http://rmforall.blogspot.com/2010_08_01_archive.htm
Sunday, August 22, 2010
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http://groups.yahoo.com/group/astrodeep/message/60
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Rich Murray, MA
Boston University Graduate School 1967 psychology,
BS MIT 1964, history and physics,
1943 Otowi Road, Santa Fe, New Mexico 87505
505-501-2298 [hidden email]

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