We know: “time crystals” sound like something out of a movie. And not a good movie, either – probably something from the same scriptwriter who came up with “unobtainium”. However, not only are they real, but they’re actually much cooler than anything Hollywood could come up with. They break the laws of physics. They turn up in children’s gifts. They were thought to be impossible for years, and then we found like, half a dozen in the space of a few years.
Since they may hold the key to the technology of the future, it’s probably best we get to grips with them. So here it is: what they are, why they’re awesome – and how, just maybe, you might be able to get one of your very own.
What exactly is a “time crystal”?
Despite the name, a time crystal is not actually a crystal. At least, not the kind you’re thinking of.
“A crystal is a system of many atoms that, due to mutual interactions, organize themselves into a periodic pattern in space,” Kostyantyn Kechedzhi, a staff research scientist at Google, told IEEE Spectrum in 2021.
A time crystal, meanwhile, “is a quantum system of many particles that organize themselves into a periodic pattern of motion – periodic in time rather than in space – that persists in perpetuity,” Kechedzhi explained.
Get the idea? While a normal crystal is defined by its super-ordered system of atoms in space – so that you can move left and right and through and back and so on and the whole thing will look the exact same – a time crystal has that, but through time (go figure). You can think of it as a more complicated version of our own Earth-moon system, kind of: two objects that orbit a barycenter and return to the same positions relative to each other on a regular period.
Of course, that’s an overly simple illustration. Time crystals don’t really consist only of two objects: “the key novelty of a time crystal is the periodic motion of a system of many objects interacting with each other,” Kechedzi said. In reality, planetary motion is a terrible candidate for a time crystal: “the true behavior of planets is chaotic,” Kechezdi explained, “which means a small deviation of a planet from its path today will result in a completely reshaped trajectory over time, albeit billions of years.”
But if you’re looking for a headline, here it is: what is a time crystal? It’s probably the first ever human-invented phase of matter.
They are "something that doesn’t actually exist in nature,” Loughborough University physics researcher Achilleas Lazarides told NBC News in 2022. “As far as we know, we created this phase of matter.”
Why should I care (or: Thermodynamics who?)
There’s no doubt about it: among the quantum physics crowd, time crystals are a very big deal.
“A time crystal keeps moving and repeats itself periodically in time in the absence of external encouragement,” Samuli Autti, a research fellow in the physics department of Lancaster University, told Live Science in 2022.
“This means they are perpetual motion machines, and therefore impossible.”
How, then, can they exist at all? The key is in that word “quantum” – the space where cats can be simultaneously alive and dead at once, and light can be both a particle and a wave at the same time. In both these seemingly paradoxical examples, the apparent conflict is due to what’s known as the “observer effect”: in quantum mechanics, particles exist in a superposition state – that is, all possible states at once – until somebody looks at them and, by doing so, causes the superposition to collapse.
And it’s this kind of weirdness that lets time crystals if not break, then certainly bend, the laws of thermodynamics. “In quantum physics, a perpetual motion machine is fine as long as we keep our eyes closed,” Autti said. “It must only start slowing down if we observe the motion.”
As long as we’re only side-eyeing them, time crystals may hold the key to resolving some of the most stubborn disconnects in modern physics. “The continuum from quantum physics to classical physics remains poorly understood,” Autti said. “Time crystals span a part of the interface between the two worlds. Perhaps we can learn how to remove the interface by studying time crystals in detail.”
Some experts claim the crystals have the power to illuminate the nature of time itself. “However much you try to treat [time] as being just another dimension, it is always kind of an outlier” in classical physics, Chetan Nayak, a research engineer at Microsoft Station Q, University of California, Santa Barbara told Quanta Magazine in 2021. But when time crystals enter the picture, “all of a sudden time is just one of the gang."
Wow, that sounds cool! Not very useful, though…
Yeah, okay – we admit it: time crystals are, at least for now, pretty useless outside of the research physicist crowd. But that doesn’t mean they always will be – and according to those who study them, time crystals are full of potential.
“A time crystal is, like ferromagnetism or superconductivity, an example of spontaneous symmetry breaking, or spontaneous order,” Kechedzi noted.
This puts time crystals in the same league as utopian tech such as superconductors or ferromagnetism, he explained – except that, even among these celebs of the physics world, time crystals have something unique going on.
“Spontaneous symmetry breaking is associated with equilibrium,” he told IEEE. Liquid water, for example, becomes ice when the ambient temperature drops low enough; the hydrogen and oxygen atoms that make it up settle into the state with the lowest energy possible, and eventually, their properties become stable.
Time crystals, on the other hand, play by different rules: they break time-translation symmetry. And they’re the only things in the universe known to do so.
“A remarkable property of the time crystal we observed is its spontaneous order despite it being driven out-of-equilibrium,” Kechedzi said.
“Stable examples of spontaneous symmetry breaking […] often have significant technological value.”
Precisely what that value will be – well, that remains to be seen. The door is open, however: “time crystals can be used as a building block for quantum devices that work also outside the laboratory,” Autti told Live Science.
“Maybe time crystals will eventually power some quantum features in your smartphone,” he told NBC.
Great! Where do I get one?
If you want to get your hands on a time crystal, you’d better have a physics lab at your disposal – they are, frankly, finicky little buggers to get a hold of.
Most successful breakthroughs have involved the use of supercomputers – like Google’s Sycamore quantum computing hardware, which was used to realize a time crystal in 2021 by Stanford researchers along with Kechedzi and his colleagues – or the ability to cool gases down to microscopic temperatures, as Autti and his colleagues did last year.
In fact, time crystals are so difficult to create that, until physicists at the University of Maryland semi-accidentally discovered one in 2017, their very existence was thought to be impossible. Even now, with a handful of success stories in the headlines, we don’t have anything long-term: “after a sufficiently long time, the order is lost and the periodic pattern no longer repeats itself,” Kechedzi admitted.
Still, if you’re really intent on finding one, there is an alternative to all that hifalutin’ laboratory tech – and it’s kind of delightful, actually. Back in 2018, just one year after the first time crystals were created, researchers from Yale University discovered signs of one hiding in a rather unusual place. Not in a quantum processor; not in a super-cooled tube of hydrogen – but in a kid’s toy.
“My student Jared Rovny had grown monoammonium phosphate (MAP) crystals for a completely different experiment, so we happened to have one in our lab,” Yale physics professor Sean Barrett said at the time.
Strip away the chemistry jargon, and what you’re looking at there is a grow-your-own crystal kit – the kind you might give to a kid as a neat science experiment on a rainy afternoon.
“Our crystal measurements looked quite striking right off the bat,” he said. “Our work suggests that the signature of a DTC could be found, in principle, by looking in a children’s crystal growing kit.”
So, aunts and uncles of the world, beware: next time you gift your niblings a slightly nerdy pastime, you might just be setting the stage for the discovery of a brand new state of matter.
All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.