Really Strange and Really Real
It's confirmed. Time crystals can exist. Two teams of researchers, one from Harvard University and the other from the University of Maryland, had their peer-reviewed work on time crystals published today in the journal Nature. The Harvard-based team used an experimental setup that created an artificial lattice in a synthetic diamond. The Maryland team, on the other hand, continued on their previous work using a chain of charged particles called ytterbium ions.
"We’ve taken these theoretical ideas that we’ve been poking around for the last couple of years and actually built it in the laboratory."
Both studies built off of time crystal theories developed from Princeton University. "Our work discovered the essential physics of how time crystals function," said Princeton's Shivaji Sondhi. "What is more, this discovery builds on a set of developments at Princeton that gets at the issue of how we understand complex systems in and out of equilibrium, which is centrally important to how physicists explain the nature of the everyday world."
Unlike other, more conventional crystals, time crystals are lattices that repeat not just in space but also in time, breaking what is known as time-translation symmetry. A time crystal is a quantum phenomenon that has movement while remaining in its ground, or lowest energy, state. In other words, it moves without spending energy and does not settle into a thermal equilibrium. It's one of the first examples of a non-equilibrium phase of matter.
Sondhi used the analogy of periodically squeezing a sponge to explain the system: "When you release the sponge, you expect it to resume its shape. Imagine now that it only resumes its shape after every second squeeze even though you are applying the same force each time. That is what our system does."
Pushing Physics Forward
This strange matter, first proposed in 2012 by physicist and Nobel laureate Frank Wilczek, was only considered theoretically possible — after considerable debate — in September of 2016. Then, the first-ever time crystal was made just a month later in October. By then, it seemed very clear that time crystals are real.
We've known since earlier this year that these two teams were developing ways to actually create time crystals. Their published works further confirm that time crystals can, indeed, exist, and one possible application for this new phase of matter is in quantum computing. Because the quantum behavior in a time crystal isn't affected by outside forces, researchers see it as a potential tool for protecting information in quantum computers.
That's all still far off. For now, work on time crystals is focused on helping us better understand physics. "Although any applications for this work are far in the future, these experiments help us learn something about the inner workings of this very complex quantum state," said Chris Monroe, who led the Maryland team.
"This opens the door to a whole new world of nonequilibrium phases," Andrew Potter, who was part of the Maryland team, told Science Daily. "We've taken these theoretical ideas that we've been poking around for the last couple of years and actually built it in the laboratory. Hopefully, this is just the first example of these, with many more to come."
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