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[Gord Green]

Time crystals: A new state of matter that outlasts the universe

https://www.newscientist.com/article/mg23431240-200-time-crystals-the-loopy-gizmos-that-repeat-their-tricks-forever/

A bizarre oscillating material that seems to run on a never-ending loop has apparently been made in the lab, bending the cast-iron laws of thermodynamics

By Shannon Palus

IT'S LIKE something out of a bad dream. You're stuck in a dance hall performing an interminable waltz. The hours go by and the dance continues. The hours melt into days, years, centuries, millennia. Eventually, billions of years have passed in which the universe has transformed into a featureless void populated only by you and your fellow indefatigable waltzers, dancing throughout eternity.

The vision is surreal, nightmarish — and entirely against the laws of physics. Anything that repeats on loop without an external energy source to power it seems to bend the cast-iron laws of thermodynamics, which govern how energy flows and can be exploited. So when five years ago, Nobel laureate Frank Wilczek speculated about a type of material that he called time crystals whose components could, in fact, do just that, he faced a wave of scepticism. "I took a lot of grief," he says.

In the time since, Wilczek's brainchildren have been championed, vilified, proved to be impossible, and now, apparently, made in the lab. If so, it's the birth of an entirely new phase of matter, one that is fundamentally bizarre, perhaps confounding — and possibly even useful.

Time crystals might still be waiting to be invented if Wilczek were not the sort of person who gets bored easily. He won his Nobel prize in 2004 for theoretical insights into the nature of the strong force, which determines how fundamental particles interact within the atomic nucleus.

He once described the experience of waiting for experimental verification of his theory as akin to watching grass grow.

In February 2012, the Nobel Prize-winning physicist Frank Wilczek decided to go public with a strange and, he worried, somewhat embarrassing idea.

Impossible as it seemed, Wilczek had developed an apparent proof of "time crystals" — physical structures that move in a repeating pattern, like minute hands rounding clocks, without expending energy or ever winding down. Unlike clocks or any other known objects, time crystals derive their movement not from stored energy but from a break in the symmetry of time, enabling a special form of perpetual motion.

"Most research in physics is continuations of things that have gone before," said Wilczek, a professor at the Massachusetts Institute of Technology. This, he said, was "kind of outside the box."

Original story reprinted with permission from Simons Science News, an editorially independent division of SimonsFoundation.org whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.

Wilczek's idea met with a muted response from physicists. Here was a brilliant professor known for developing exotic theories that later entered the mainstream, including the existence of particles called axions and anyons, and discovering a property of nuclear forces known as asymptotic freedom (for which he shared the Nobel Prize in physics in 2004).

But perpetual motion, deemed impossible by the fundamental laws of physics, was hard to swallow. Did the work constitute a major breakthrough or faulty logic?

Jakub Zakrzewski, a professor of physics and head of atomic optics at Jagiellonian University in Poland who wrote a perspective on the research that accompanied Wilczek's publication, says: "I simply don't know."

Now, a technological advance has made it possible for physicists to test the idea. They plan to build a time crystal, not in the hope that this perpetuum mobile will generate an endless supply of energy (as inventors have striven in vain to do for more than a thousand years) but that it will yield a better theory of time itself.

A Crazy Concept

The idea came to Wilczek while he was preparing a class lecture in 2010. "I was thinking about the classification of crystals, and then it just occurred to me that it's natural to think about space and time together," he said. "So if you think about crystals in space, it's very natural also to think about the classification of crystalline behavior in time."

When matter crystallizes, its atoms spontaneously organize themselves into the rows, columns and stacks of a three-dimensional lattice.

An atom occupies each "lattice point," but the balance of forces between the atoms prevents them from inhabiting the space between. Because the atoms suddenly have a discrete, rather than continuous, set of choices for where to exist, crystals are said to break the spatial symmetry of nature — the usual rule that all places in space are equivalent. But what about the temporal symmetry of nature — the rule that stable objects stay the same throughout time?

Wilczek mulled over the possibility for months. Eventually, his equations indicated that atoms could indeed form a regularly repeating lattice in time, returning to their initial arrangement only after discrete (rather than continuous) intervals, thereby breaking time symmetry. Without consuming or producing energy, time crystals would be stable, in what physicists call their "ground state," despite cyclical variations in structure that scientists say can be interpreted as perpetual motion.

"For a physicist, this is really a crazy concept to think of a ground state which is time-dependent," said Hartmut H??ffner, a quantum physicist at the University of California, Berkeley. "The definition of a ground state is that this is energy-zero. But if the state is time-dependent, that implies that the energy changes or something is changing. Something is moving around."

How can something move, and keep moving forever, without expending energy? It seemed an absurd idea — a major break from the accepted laws of physics. But Wilczek's papers on quantum and classical time crystals (the latter co-authored by Alfred Shapere of the University of Kentucky) survived a panel of expert reviewers and were published in Physical Review Letters in October 2012. Wilczek didn't claim to know whether objects that break the symmetry of time exist in nature, but he wanted experimentalists to try to make one.

"It's like you draw targets and wait for arrows to hit them," he said. "If there's no logical barrier to this behavior being realized, then I expect it will be realized."

The Big Test

In June, a group of physicists led by Xiang Zhang, a nanoengineer at Berkeley, and Tongcang Li, a physicist and postdoctoral researcher in Zhang's group, proposed creating a time crystal in the form of a persistently rotating ring of charged atoms, or ions. (Li said he had been contemplating the idea before reading Wilczek's papers.) The group's article was published with Wilczek's in Physical Review Letters.

Since then, a single critic — Patrick Bruno, a theoretical physicist at the European Synchrotron Radiation Facility in France — has voiced dissent in the academic literature. Bruno thinks Wilczek and company mistakenly identified time-dependent behavior of objects in excited energetic states, rather than their ground states. There is nothing surprising about objects with surplus energy moving in a cyclical fashion, with the motion decaying as the energy dissipates. To be a time crystal, an object must exhibit perpetual motion in its ground state.

A space-time crystal, time crystal, or four-dimensional crystal, is a structure periodic in time and space. Normal three-dimensional crystals will stay the same after any period of time, but time crystals change from moment to moment, repeating themselves after a fixed interval of time. The term was coined by the scientist David Wang.[citation needed] It extends the idea of a crystal to four dimensions.

Analogues of the space-time crystal have been made that are in a non-equilibrium state, and need an external drive to repeat in time.

They are a newly confirmed form of matter.

Time crystals cannot exist as a lowest energy state, and in changing to the lowest energy state would change to a static state that was not a time crystal. However with external influences they can be kept from the lowest energy state and be forced to repeat indefinitely. This means that a time crystal must be part of an open system where energy comes from the outside. A time crystal is an open system in non-equilibrium with its environment that exhibits time translation symmetry breaking (TTSB).

In March 2017, it was reported that the theoretical concept of time crystals had been proven, showing that it is possible for these crystals to exist out of equilibrium with their environment over time.

The idea of a time crystal was first put forward by Nobel laureate and MIT professor Frank Wilczek in 2012.

Space-time crystals extend the ordinary three-dimensional symmetry seen in crystals to include the fourth dimension of time; a time crystal spontaneously breaks the symmetry of time translation. The crystal's pattern repeats not in space, but in time, which allows for the crystal to be in perpetual motion.

Time crystals are closely related to the concepts of zero-point energy and the dynamical Casimir effect.

In 2015 Krzysztof Sacha, from Jagiellonian University in Krakow, Poland, showed that time crystals phenomenon can be observed in a periodically driven many-body system.

In 2016, Norman Yao and his colleagues from the University of California, Berkeley, put forward a concrete proposal that would allow time crystals to be created in a laboratory environment. Yao's blueprint was then used by two teams, a group led by Christopher Monroe at the University of Maryland[d] and a group led by Mikhail Lukin at Harvard University,[e] who were both able to successfully create a time crystal. Both experiments were published in the journal Nature in March 2017.

Time crystals are thought to exhibit topological order, an emergent phenomenon, in which correlations between the two particles that work together in an entangled system are encoded in the whole wave-function of a system and allow for fault tolerance against perturbations, thus allowing quantum states to stabilize against decoherence effects that usually limit their useful lifetime. Preventing decoherence has a wide range of implications: The efficiency of some information theory and quantum thermodynamic tasks can be greatly enhanced when using quantum correlated states. It is also thought that time crystals could provide deeper understanding of the theory of time.

This is a concept difficult to wrap your mind around, but it would make a GREAT basis for a time travel story!

There MUST be some on this forum capable of using this data to tell a groundbreaking saga using this as a springboard! ( Do you hear me Bruce? )

Gord
star pirate