March 06, 2012

Quantum biology on the transition of chaos increase coherence times by orders of magnitude

A new mechanism in quantum biology could be exploited to enable lossless quantum coherent energy and information processing devices at room temperature.

Arxiv - Quantum biology on the edge of quantum chaos (6 pages)

We give a new explanation for why some biological systems can stay quantum coherent for long times at room temperatures, one of the fundamental puzzles of quantum biology. We show that systems with the right level of complexity between chaos and regularity can increase their coherence time BY orders of magnitude. Systems near Critical Quantum Chaos or Metal-Insulator Transition (MIT) can have long coherence times and coherent transport at the same time. The new theory tested in a realistic light harvesting system model can reproduce the scaling of critical fluctuations reported in recent experiments. Scaling of return probability in the FMO light harvesting complex shows the signs of universal return probability decay observed at critical MIT. The results may open up new possibilities to design low loss energy and information transport systems in this Poised Realm hovering reversibly between quantum coherence and classicality.

Technology Review - this is an interesting mechanism that, if verified experimentally, could have an important impact on quantum engineering. The critical transition that Kauffman and co talk about is also known as the the metal-to-insulator transition, which allows the transport of quantum information and energy. If that can be made to work at room temperature, as Kauffman and co suggest, all kinds of new quantum devices may be possible.

"The results may open up new possibilities to design low loss energy and information transport systems," they say.




The fi ndings support a new approach to quantum biological systems. They are not just under the influence of environmental decoherence due to random noise but also driven by the coherent waves of the incoming photons. The photons are absorbed by one of the chromophores which can be interpreted as a measurement process selecting one of the chromophores randomly. Then the system is set into an initial state which is concentrated on the selected chromophore. The purity of the system becomes P = 1 as this is a pure state and the partially decoherent evolution starts again decreasing the purity in time. The system can hover in the "Poised Realm" between clean quantum and incoherent classical worlds. By tuning the timings of re-coherence events and the coherence time during decoherence via tuning the system on the chaos-regularity axis can be kept in high level of purity.

We hope that the mechanism discovered here makes it possible to create new quantum devices working at room temperature tuned to critical MIT capable of nearly frictionless quantum transport of energy and information.

Discovery of room temperature quantum coherence in the avian compass of birds, in the olfactory receptors and in light harvesting complexes in the last few years indicate that quantum eff ects might be ubiquitous in biological systems. While the quantum chemical understanding of the details of light harvesting systems is almost complete, no organizing principle has been found which could explain why quantum coherence is maintained in these systems for much longer than the characteristic decoherence time imposed by their room temperature environment. Here we propose that at the critical edge of quantum chaos coherence and transport can coexist for several orders of magnitudes longer than in simple quantum systems. Quantum systems changing from integrable to quantum chaotic pass through critical quantum chaos which is also a metal-insulator transition from Anderson localization to extended wave functions. By extending the semiclassical theory of decoherence from chaotic and integrable systems to the transition region we show that coherence decay changes from exponential to power law behavior and coherence time is amplifi ed exponentially from its environmentally determined value. We demonstrate our theory on a ring of chromophores passing through the critical point and show that coherence in the critical point decays with the same non-trivial power law as in the FMO complex experiment. Our results also suggest that loss of coherence is not permanent in these systems and they can re-cohere via coherent external driving such as the arrival of photons in case of the light harvesting systems and can continuously hover in the "Poised Realm" between the coherent quantum and the incoherent classical worlds. Using this new critical design principle from biology might open the way to build lossless quantum coherent energy and information processing devices operating at room temperature.

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