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posted by martyb on Wednesday April 04 2018, @08:01PM   Printer-friendly
from the if-I-could-turn-back-time dept.

Quantum Correlations Reverse Thermodynamic Arrow of Time

A team of physicists has made heat flow spontaneously from a cold quantum object to a hot one. The experiment underscores the intimate relationships between information, entropy and energy that are being explored in the nascent field of quantum thermodynamics.

The team, based in Brazil, took a molecule that consisted of a carbon atom, a hydrogen atom and three chlorine atoms. They then generated a magnetic field to align the nuclear spins of the two quantum particles, or "qubits" — the carbon and hydrogen nuclei. This caused the nuclei to become linked, or correlated, turning them into a single, inseparable whole, a two-qubit quantum state.

[...] If the total entropy suddenly decreased in a regular, uncorrelated system, it would violate the second law. But here, the researchers take the correlation into account. The weakening of the correlation is akin to a "fuel driving the heat from the colder to the hotter body," said David Jennings, a physicist at Imperial College London. The cold qubit gets colder, the hot qubit hotter. In other words, heat flows from cold to hot. This occurs because of "a trade-off between correlations and entropy," said Roberto Serra, a physicist at the Federal University of ABC and the head of the research group behind the study.

The operation effectively reverses the arrow of time, at least in this isolated system. "The thermodynamic arrow of time relies on the notion that the entropy of a closed system can only increase or remain constant, but never decrease," Micadei said. "By creating in the lab an isolated system where the entropy decreases, in the system the arrow of time should point to the opposite direction."

Also at Oregon Public Broadcasting, which bravely names the molecule.


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  • (Score: 3, Funny) by mrchew1982 on Wednesday April 04 2018, @10:21PM (1 child)

    by mrchew1982 (3565) on Wednesday April 04 2018, @10:21PM (#662666)

    If a force from outside of the system interacts with that system and in fact causes this miraculous thing that science says is impossible, then the boundary for that system must be redrawn to include that outside force as part of that system!

    E.g. Maxwell's demon. If you include the work that the "demon" puts into the system it follows all of the existing laws of physics and thermodynamics!

    It's like saying that plants reverse entropy. They kinda do, because they create ordered structures out of chaotic building blocks... But when you include the entropy that happened in the sun to provide the energy that gave the plant enough energy to do that... it's still following the laws of the universe, the arrow of time stays irreversible and entropy prevails.

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  • (Score: 0) by Anonymous Coward on Thursday April 05 2018, @12:18AM

    by Anonymous Coward on Thursday April 05 2018, @12:18AM (#662698)

    I'm not sure why this was marked as funny, because it was effectively the same argument I was going to say.

    I am not a physicists, and I don't know the details of the experiment. However, on the surface, this sounds as silly as saying:

    "I know the perfect way to rig the stock market. I can buy any stock you buy guaranteed it goes up in value. Easy! Just give me an extra $3 trillion USD to buy more of the same stock, and I guarantee that the stock you bought will increase in value."

    If you throw extra energy in the system (including but not limited to a magnetic field), of course you can locally decrease entropy. But then, it's not a "closed system," is it?

    But I guess that's a less catchy headline than saying we can reverse the flow of time...