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A new look at Entropy, Quantum biology?

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An article in the May 27th issue of Quanta Magazine discussed a new understanding of the second law of thermodynamics ( ). It points out that the second law has been thought of to be just about statistics: It’s a law of large numbers. In this view, there’s no fundamental reason why entropy can’t decrease — why, for example, all the air molecules in your room can’t congregate by chance in one corner. It’s just extremely unlikely.

But the laws of classical physics are deterministic — they allow only a single outcome for any starting point. Where, then, can that hypothetical ensemble of air molecules states enter the picture at all, if only one outcome is ever possible?

There’s no statistical aspect to it. Irreversibility is not just the most probable outcome but the inevitable one, governed by the quantum interactions of the component’s entanglement with the environment, entanglement in which information is lost.

For the new theory, physicists consider a transformation involving the states of quantum bits (qubits), which can exist in one of two states or in a combination, or superposition, of both. In their model, a single qubit B may be transformed from some initial, perfectly known state B1 to a target state B2 when it interacts with other qubits by moving past a row of them one qubit at a time. This interaction entangles the qubits: Their properties become interdependent, so that you can’t fully characterize one of the qubits unless you look at all the others too. The process of sequential interactions of B with the row of qubits constitutes a constructor-like machine that transforms B1 to B2.

You can approximate the constructor arbitrarily well in one direction but not the other. There’s an asymmetry to the transformation, just like the one imposed by the second law. This is because the transformation takes the system from a so-called pure quantum state (B1) to a mixed one (B2, which is entangled). A pure state is one for which we know all there is to be known about it. But when two objects are entangled, you can’t fully specify one of them without knowing everything about the other too. It’s easier to go from a pure quantum state (for biologists this could be a living organism or a species) to a mixed state (like a distribution following death and decomposition) than vice versa — because the information in the pure state gets spread out by entanglement and is hard to recover. It’s comparable to trying to re-form a droplet of ink once it has dispersed in water, a process in which the irreversibility is imposed by the second law.

So here the irreversibility is “just a consequence of the way the system dynamically evolves. There’s no statistical aspect to it. Irreversibility is not just the most probable outcome but the inevitable one, governed by the quantum interactions of the components. “Our conjecture,” claim the physicists, “is that thermodynamic irreversibility might stem from this.” The discarding of information — or the inability to keep track of it — is really the reason why the second law holds.

Closer to the realm of biology, there is a powerful new research line called Quantum Biology by its leader, Vladimiro Mujica. “We're trying to decipher in a way, a mystery of nature and evolution,” Mujica said. “Because it turns out that biological systems use these chiral molecules in proteins, DNA and RNA. These are some of the most important molecules in biology. For example, DNA is a double-helix ladder that is intrinsically chiral. And so are the proteins encoded by these fundamental biological molecules, which are the bricks and mortars of the cell, doing all the work that makes us alive”. Mujica leads a multi-institutional quantum biology team that includes Arizona State University colleague William Petuskey and leading experimentalists, including Northwestern University co-investigators Michael Wasielewski and University of California Los Angeles professors Paul Weiss and Louis Bouchard. ( )


This topic was modified 2 months ago by Dr. Carl Jordan
This topic was modified 2 months ago 4 times by Gabe Brauer
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Quantum Biology posits that entropy is not a statistical phenomenon but rather a deterministic one. While a statistical approach means that reversal of entropy is possible but highly unlikely, Quantum Biology says that it is impossible. Regardless, neither approach will negate thermodynamic theory that complex organisms will decompose and disintegrate. What puzzles me is why physicists never ask (at least to my knowledge) how the complexity of living organisms was synthesized in the first place, since it would seem to contradict the second law of thermodynamics. Evangelicals explain it by saying God did the synthesis, but that is not an explanation, but merely putting a label on an unknown phenomenon. In chapter 12, I point out that some biologists have hypothesized that autocatalysis during a recycling phase of ecosystem evolution is responsible, but the details of the mechanism are lacking. I would be very interested in a physicist’s view of how during evolution, information moves from an entangled state to a pure quantum state where it is well organized.



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