Do some particles defy the universe’s push for disorder?

rubidium/Dnn87 (CC BY 3.0)

That’s an apparent implication of a recent experiment. Generally, left to itself, “a system strives toward equilibrium with its environment” or, in plain terms, “things always go downhill.” They spoil, they crumble, they disintegrate. Sandcastles become sand. Except:

It’s common and intuitive, and precisely what a team of physicists expected to see when they lined up 51 rubidium atoms in a row, holding them in place with lasers. The atoms started in an orderly pattern, alternating between the lowest-energy “ground” state and an excited energy state. The researchers assumed the system would quickly thermalize: The pattern of ground and excited states would settle almost immediately into a jumbled sequence.

And at first, the pattern did jumble. But then, shockingly, it reverted to the original alternating sequence. After some more mixing, it returned yet again to that initial configuration. Back and forth it went, oscillating a few times in under a microsecond — long after it should have thermalized.

It was as if you dropped an ice cube in hot water and it didn’t just melt away, said Mikhail Lukin, a physicist at Harvard University and a leader of the group. “What you see is the ice melts and crystallizes, melts and crystallizes,” he said. “It’s something really unusual.” Marcus Woo, “Quantum Machine Appears to Defy Universe’s Push for Disorder” at Quanta

As Woo goes on to explain, physicists call this “quantum many-body scarring,” with one idea being that the atoms “remember” a past state and return to it, though just how they remember is unclear The work was being done as part of a push for quantum computing.

“There is some beautiful structure that somehow coexists with a totally random environment,” Papić said. “What kind of physics allows this to happen? This is a kind of deep and profound question that runs through many areas of physics, and I think this is another incarnation.” Marcus Woo, “Quantum Machine Appears to Defy Universe’s Push for Disorder” at Quanta

Won’t argue.

Note: rubidium

Paper.  (paywall)

See also: Whether Or Not Man Has Free Will, Quantum Mechanics Means That Nature Does

If quantum mechanics were a researcher, she’d be fired

Quantum Mechanics: Pushing The “Free-Will Loophole” Back To 7.8 Billion Years Ago

At Nature: For Now, “Uncertainty Seems The Wisest Position” On The Implications Of Quantum Mechanics

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and

Is the search for meaning in quantum physics a form of religion?

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