By Tom
Metcalfe
Physicists in Finland are the latest scientists to create "time crystals," a newly discovered phase of matter that exists only on minuscule atomic scales and extremely low temperatures, but also appears to defy a fundamental law of nature: the prohibition of perpetual motion
The effect is only observed under quantum mechanical conditions (which is how atoms and their particles interact) and any attempt to extract work from such a system will destroy it.
But the research reveals more of the counterintuitive nature of the quantum realm, the smallest scale in the universe that ultimately influences everything else.
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Time crystals have no practical use and are nothing like natural crystals.
In fact, they look nothing alike.
Instead, the name "time crystal" - of which any marketing executive would be proud - describes its regular changes of quantum states over a period of time, rather than its regular forms in physical space, like ice, quartz or diamond.
Some scientists suggest that time crystals could one day serve as memory for quantum computers.
But the more immediate goal of this work is to learn more about quantum mechanics, according to physicist Samuli Autti, a professor and researcher at Lancaster University, UK.
And just as the modern world depends on quantum mechanical effects inside transistors, there is a chance that these new quantum artifacts will one day prove useful.
"Maybe time crystals will end up powering some quantum functions in your
smartphone
," says Autti.
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Autti is the lead author of a study published in Nature Communications last month that describes the creation of two individual time crystals within a helium sample and their magnetic interactions as they change shape.
He and his colleagues at the Low Temperature Laboratory at Aalto University in Helsinki started with helium gas in a glass tube, then cooled it with lasers and other laboratory equipment to just one ten-thousandth of a degree above absolute zero (about 459.67 degrees Fahrenheit below zero).
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The researchers then used the scientific equivalent of "peering" their helium sample with radio waves, so as not to disturb its fragile quantum states, and observed that some of the helium nuclei oscillated between two low-energy levels, indicating that they had formed a "crystal" over time.
At such low temperatures, matter does not have enough energy to behave normally, so it is dominated by quantum mechanical effects.
For example, helium - a liquid at less than 452.2 Fahrenheit - has no viscosity or "thickness" in this state, so it flows upwards out of containers as what's called a "superfluid."
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The study of time crystals is part of quantum physics research, which can quickly become puzzling.
At the quantum level, a particle can be in more than one place at a time, or it can form a
qubit
, the quantum analog of a single bit of digital information, but which can have two different values at the same time.
Quantum particles can also entangle and teleport.
Physicists haven't figured it all out yet.
Time crystals are one of the many strange features of quantum physics.
In normal crystals, such as ice, quartz or diamond, the atoms are aligned in a specific physical position, a tiny effect that gives rise to their peculiar regular shapes on a larger scale.
The researchers cooled a helium-3 superfluid to within one ten-thousandth of a degree from absolute zero and proceeded to create two time crystals within the liquid.Mikko Raskinen/Aalto University
But the particles of a time crystal exist in one of two different low-energy states, depending on when you look at them, that is, their position in time.
The result is a regular oscillation that continues forever, a true type of perpetual motion.
However, such perpetual motion only really exists forever in ideal time crystals that have not been fixed in one state or another, and since the time crystals in the Aalto University experiments were not ideal, they only lasted a few minutes before to “melt down” and start behaving normally, Autti said.
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The same limitation means there's no way to exploit perpetual motion: A time crystal would simply stop — "melt" — if you tried to extract physical work from it, he said.
Time crystals were first proposed in 2012 by the American theoretical physicist Frank Wilczek, who received the Nobel Prize in Physics in 2004 for his work on the "strong" subatomic force that keeps quarks inside protons and neutrons. atomic nuclei, one of the fundamental forces of the universe.
They were first detected in 2016 in experiments with ions of the rare earth metal ytterbium at the University of Maryland.
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Time Crystals have only been made a handful of times since then, as they are extremely difficult to create.
But experiments at Aalto University point to a way to make them easier and longer.
It is also the first time that two time crystals have been used to form any kind of system.
Physicist Achilleas Lazarides, a professor at Loughborough University, UK, conducted theoretical research on time crystals that contributed to the creation of a working quantum simulation of time crystals on a specialized quantum computer operated by tech giant Google.
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Lazarides, who was not involved in the latest study, explained that the perpetual motion of time crystals occurs outside the laws of thermodynamics, developed in the 19th century from earlier ideas about energy conservation.
It is generally stated that the total work energy of a system can only decrease, which means that perpetual motion is impossible, something that has been confirmed by centuries of experiments.
But quantum changes in the low-energy states of the nuclei in time crystals do not create or use energy, so the total energy of such a system never increases, a special case that is allowed by the laws of science. thermodynamics, he said.
Lazarides acknowledged that current experiments with time crystals are far from any practical application whatever, but the potential to learn more about quantum mechanics is invaluable.
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Time crystals are "something that doesn't really exist in nature," he said.
“As far as we know, we have created this phase of matter.
It's hard to know if anything will come out of it,” he concluded.