Does the nature know about and use quantum effects more than we do?
Credit: iStockphoto
SYDNEY: Quantum effects are used to absorb and move around light energy during photosynthesis, scientists said, and its the first time such long-lived effects have been seen in this temperature range.
Photosynthesis is crucial to the evolution of life, but until now the way that proteins harness the energy of sunlight so effectively has long been a mystery.
Scientists have shown that two species of marine algae use a quantum state known as coherence — where light strangely exists in two places at once — to capture and transfer energy, and their results were published in the journal Nature today.
Harvesting light in solar cells
The results reveal how biological processes such as photosynthesis utilise quantum mechanics in order to survive and open up new possibilities towards harvesting light using 'organic' solar cells.
A team of scientists led by Australian chemist Greg Scholes, currently at the University of Toronto in Canada, isolated light-harvesting proteins in marine algae called cryptophytes. They stimulated the proteins with femtosecond laser pulses to mimic the absorption of sunlight.
"This enabled us to monitor the subsequent processes, including the movement of energy between special molecules bound in the protein, against a stop-clock," said Scholes.
"We were astonished to find clear evidence of long-lived quantum mechanical states involved in moving the energy.
Proteins use 'superposition'
"Our result suggests that the energy of absorbed light resides in two places at once - a quantum superposition state, or coherence - and such a state lies at the heart of quantum mechanical theory," he said.
Light-harvesting proteins are a crucial feature of photosynthesis and allow organisms to most effectively capture sunlight across a broad spectrum.
Although the functions of these proteins in photosynthesis have been observed before, this is the first time such long-lived quantum coherence has been observed at a normal temperature range.
"What we found for the cryptophytes was that such long-lived coherences exist at normal biological temperatures. It means that they play a kind of active role in light-harvesting and actually moving the energy, which opens up some quite deep questions in physics," Scholes said.
Harvesting light in solar cells
The observations also open up new possibilities towards harvesting light using 'organic' solar cells, he said.
"What we need to do in organic solar cells is work out how to move the energy of absorbed light further. By discovering how nature does this, we may find inspiration," he said.
Scholes says future research will focus on whether the quantum processes gave the algae an evolutionary advantage - after bacteria, algae were one of the first organisms to evolve on Earth and still thrive today.
Biological-quantum connection is "oversold"
"It suggests that algae knew about quantum mechanics nearly two billion years before humans," he said.
But Australian physicist Ross McKenzie from the University of Queensland in Brisbane, author of a blog on quantum physics effects (condensedconcepts.blogspot.com) said while the research techniques were commendable, the significance of the quantum-mechanics effect for biological molecules was "oversold".
"Based on past experience, I predict this work will be misrepresented by those who desperately want to believe that bizarre quantum effects such as entanglement are crucial to biomolecules being able to function in an optimum manner. I see no evidence for such claims in this experimental data."
Follow Cosmos on Twitter!
twitter.com/cosmosmagazine
