Quantum Physics Discoveries Could Change Face of Technology

[The SC]

Unusual Quantum Effect Discovered in Earliest Stages of Photosynthesis

TEHRAN (FNA)- Quantum physics and plant biology seem like two branches of science that could not be more different, but surprisingly they may in fact be intimately tied.


Researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory and the Notre Dame Radiation Laboratory at the University of Notre Dame used ultrafast spectroscopy to see what happens at the subatomic level during the very first stage of photosynthesis. "If you think of photosynthesis as a marathon, we're getting a snapshot of what a runner looks like just as he leaves the blocks," said Argonne biochemist David Tiede. "We're seeing the potential for a much more fundamental interaction than a lot of people previously considered."

While different species of plants, algae and bacteria have evolved a variety of different mechanisms to harvest light energy, they all share a feature known as a photosynthetic reaction center. Pigments and proteins found in the reaction center help organisms perform the initial stage of energy conversion.

These pigment molecules, or chromophores, are responsible for absorbing the energy carried by incoming light. After a photon hits the cell, it excites one of the electrons inside the chromophore. As they observed the initial step of the process, Argonne scientists saw something no one had observed before: a single photon appeared to excite different chromophores simultaneously.

"The behavior we were able to see at these very fast time scales implies a much more sophisticated mixing of electronic states," Tiede said. "It shows us that high-level biological systems could be tapped into very fundamental physics in a way that didn't seem likely or even possible."

The quantum effects observed in the course of the experiment hint that the natural light-harvesting processes involved in photosynthesis may be more efficient than previously indicated by classical biophysics, said chemist Gary Wiederrecht of Argonne's Center for Nanoscale Materials. "It leaves us wondering: how did Mother Nature create this incredibly elegant solution?" he said.

The result of the study could significantly influence efforts by chemists and nanoscientists to create artificial materials and devices that can imitate natural photosynthetic systems. Researchers still have a long way to go before they will be able to create devices that match the light harvesting efficiency of a plant.

One reason for this shortcoming, Tiede explained, is that artificial photosynthesis experiments have not been able to replicate the molecular matrix that contains the chromophores. "The level that we are at with artificial photosynthesis is that we can make the pigments and stick them together, but we cannot duplicate any of the external environment," he said. "The next step is to build in this framework, and then these kinds of quantum effects may become more apparent."

Because the moment when the quantum effect occurs is so short-lived -- less than a trillionth of a second -- scientists will have a hard time ascertaining biological and physical rationales for their existence in the first place. "It makes us wonder if they are really just there by accident, or if they are telling us something subtle and unique about these materials," Tiede said. "Whatever the case, we're getting at the fundamentals of the first step of energy conversion in photosynthesis."

An article based on the study appeared online in the March 12 issue of the Proceedings of the National Academy of Sciences. The research was supported by the DOE Office of Science.

 

[The SC]

Quantum Computers Will Be Able to Simulate Particle Collisions

TEHRAN (FNA)- Quantum computers are still years away, but a trio of theorists has already figured out at least one talent they may have.

According to the theorists, including one from the National Institute of Standards and Technology (NIST), physicists might one day use quantum computers to study the inner workings of the universe in ways that are far beyond the reach of even the most powerful conventional supercomputers.

Quantum computers require technology that may not be perfected for decades, but they hold great promise for solving complex problems. The switches in their processors will take advantage of quantum mechanics -- the laws that govern the interaction of subatomic particles. These laws allow quantum switches to exist in both on and off states simultaneously, so they will be able to consider all possible solutions to a problem at once.

This unique talent, far beyond the capability of today's computers, could enable quantum computers to solve some currently difficult problems quickly, such as breaking complex codes. But they could look at more challenging problems as well.

"We have this theoretical model of the quantum computer, and one of the big questions is, what physical processes that occur in nature can that model represent efficiently?" said Stephen Jordan, a theorist in NIST's Applied and Computational Mathematics Division. "Maybe particle collisions, maybe the early universe after the Big Bang? Can we use a quantum computer to simulate them and tell us what to expect?"

Questions like these involve tracking the interaction of many different elements, a situation that rapidly becomes too complicated for today's most powerful computers.

The team developed an algorithm -- a series of instructions that can be run repeatedly -- that could run on any functioning quantum computer, regardless of the specific technology that will eventually be used to build it. The algorithm would simulate all the possible interactions between two elementary particles colliding with each other, something that currently requires years of effort and a large accelerator to study.

Simulating these collisions is a very hard problem for today's digital computers because the quantum state of the colliding particles is very complex and, therefore, difficult to represent accurately with a feasible number of bits. The team's algorithm, however, encodes the information that describes this quantum state far more efficiently using an array of quantum switches, making the computation far more reasonable.

A substantial amount of the work on the algorithm was done at the California Institute of Technology, while Jordan was a postdoctoral fellow. His coauthors are fellow postdoc Keith S.M. Lee (now a postdoc at the University of Pittsburgh) and Caltech's John Preskill, the Richard P. Feynman Professor of Theoretical Physics.

The team used the principles of quantum mechanics to prove their algorithm can sum up the effects of the interactions between colliding particles well enough to generate the sort of data that an accelerator would provide.

"What's nice about the simulation is that you can raise the complexity of the problem by increasing the energy of the particles and collisions, but the difficulty of solving the problem does not increase so fast that it becomes unmanageable," Preskill says. "It means a quantum computer could handle it feasibly."

Though their algorithm only addresses one specific type of collision, the team speculates that their work could be used to explore the entire theoretical foundation on which fundamental physics rests.

"We believe this work could apply to the entire standard model of physics," Jordan says. "It could allow quantum computers to serve as a sort of wind tunnel for testing ideas that often require accelerators today."

 

[DesiGuy]

Both quantum physics and Nano technology will shape our future entirely different. The world really need to spend few billions dollars funding these organizations.