May
18

Quantum entanglement in real biological system

green plantsThe 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 at the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) 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, 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 centres. Now a new collaborative team that includes Fleming have identified entanglement as a natural feature of these quantum effects. Their work is published in the Nature Physics journal. 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.

“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 at the University of California. “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.

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.

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 centres 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 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.

Source: original article

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