One of the more exciting discoveries in biology in the last few years is the role that quantum effects seem to play in many living systems.

The two most famous examples are in bird navigation, where the quantum zeno effect seems to help determine the direction of the Earth's magnetic field, and inphotosynthesis, where the way energy passes across giant protein matrices seems to depend on long-lasting quantum coherence.

Despite the growing evidence in these cases, many physicists are uneasy, however. The problem is the issue of decoherence, how quickly quantum states can survive before they are overwhelmed by the hot, wet environment inside living things.

According to conventional quantum calculations, these states should decay in the blink of an eye, so fast that they should not be able to play any role in biology.

That's led many physicists to assume something is wrong: either the measurements are faulty in some way or there is some undiscovered mechanism that prevents decoherence.

Today, Gabor Vattay and Stuart Kauman at the University of Vermont in the US and Samuli Niiranen at the Tampere Institute of Technology in Finland say its the latter.

These guys have worked out that in certain special circumstances, quantum systems can remain coherent over much greater timescales and distances than conventional quantum thinking gives credit for. And they argue that biology exploits this process in a way that explains the recent observations from quantum biologists.

Their discussion focuses on the weird phenomenon, even by quantum standards, of quantum chaos, in which small changes to a quantum system can have a huge influence on its evolution, just as in classical chaotic systems.

When a systems changes from being merely quantum to being quantum chaotic, it passes through a kind of phase transition. The new thinking focuses on this transition.

Physicists have known for many years that when a system is finely balanced between two phases, all kinds of strange behaviour can occur. For example, water changes from a gas to a liquid to a solid at certain temperatures and pressures. These states all have well defined properties.

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Quantum Biology and the Puzzle of Coherence