Time crystals—how scientists created a new state of matter

February 22, 2017 by Rodrigo Ledesma-Aguilar, The Conversation
Credit: Shutterstock/CatyArte

Some of the most profound predictions in theoretical physics, such as Einstein's gravitational waves or Higgs' boson, have taken decades to prove with experiments. But every now and then, a prediction can become established fact in an astonishingly short time. This is what happened with "time crystals", a new and strange state of matter that was theorised, disproved, revamped and finally created in just five years since it was first predicted in 2012.

Crystals, such as diamond and quartz, are made of atoms arranged in a repeating pattern in space. In these new crystals, atoms also follow a repeating pattern, but in time. Because of this weird property, time crystals could one day find applications in revolutionary technologies such as quantum computing.

The story of time crystals begins in 2012 with Nobel Prize winner Frank Wilczek from MIT. As a theoretical physicist and a mathematician, Wilczek made a crucial step in transferring a key property of regular crystals – called symmetry breaking – to create the idea of time crystals.

To understand what symmetry breaking is, think of liquid water. In a water droplet, molecules are free to move about and can be anywhere within the liquid. The liquid looks the same in any direction, meaning that it has a high degree of symmetry. If the water freezes to form ice, attractive forces between the molecules force them to rearrange into a crystal, where molecules are spaced at regular intervals. But this regularity means that the crystal isn't as symmetrical as the liquid, so we say the symmetry of the liquid has been broken when freezing into ice.

Symmetry breaking is one of the most profound concepts in physics. It is behind the formation of crystals, but also appears in many other fundamental processes. For example, the famous Higgs mechanism, which explains how subatomic particles come to acquire mass, is a symmetry breaking process.

Back in 2012, Wilczek came up with a tantalising idea. He wondered if, in the same way that a crystal breaks symmetry in space, it would be possible to create a crystal breaking an equivalent symmetry in time. This was the first time the idea of a time crystal was theorised.

Such an object would have an intrinsic time regularity, equivalent to the crystal's regular pattern in space. For a time crystal, the pattern would be a continuous change back and forth in one of its physical properties, a kind of heartbeat that repeats forever, a bit like a machine.

Perpetual motion machines, which are machines that can work indefinitely without an energy source, are forbidden by the laws of physics. Wilczek recognised this oddity of his time crystal theory and, in 2015, another group of theoretical physicists showed a perpetual motion crystal would indeed be impossible.

Crystals have regular but asymmetrical atomic arrangements. Credit: Shutterstock/SmirkDingo

But this was not the end of the story. In 2016, new research showed that time crystals could still exist in theory, but only if there was some external driving force. The idea was that the time regularity would be somehow dormant, hidden from view, and that adding a little energy would bring it to life and unveil it. This solved the paradox of perpetual motion, and brought new hopes for the existence of time crystals.

Then, in the summer of 2016, the conditions to create and observe time crystals were laid out in an article in the online arXiv repository, and later published in the peer-reviewed journal Physical Review Letters. The researchers studied how a special property of particles known as quantum spin could be repeatedly reversed by an external force at regular intervals. They predicted that if they did this to a set of particles, the interactions between the particles would produce their own oscillations in the spin, creating a "driven" time crystal.

In a matter of months, two different experimental groups had taken on the challenge to create the time crystals in the laboratory. One of the teams fired laser pulses at a train of ytterbium atoms that produced oscillations in the atoms' properties, at different intervals from the pulses. This meant that the ytterbium atoms were behaving as a time crystal.

The other team focused on an entirely different system, consisting of impurities in a diamond crystal. They used microwaves to disturb the impurities at well-defined intervals, and observed the same type of time-crystal oscillations as the first team. At last, time crystals had been created and Wilczek's main ideas proven true.

Crystal future

The prediction, realisation and discovery of time crystals opens a new chapter in quantum mechanics, with questions about the properties of this newly found state of matter and whether time crystals might occur in nature.

The symmetry-breaking properties of ordinary crystals have lead to the creation of phononic and photonic metamaterials, deliberately designed materials that selectively control acoustic vibrations and light that can be used to boost the performance of prosthetics, or to increase the efficiency of lasers and fibre-optics. So the time properties of time crystals will likely find their way into equally novel fields, such as chrono-metamaterials for quantum computing, which uses the inherent properties of atoms to store and process data.

The story of started with a beautiful idea by a theoretical physicist, and now has culminated its first chapter with conclusive experimental evidence after a mere five years. Far from coming to an end as scientists prove their big theories, it seems physics is more alive than ever.

Explore further: Physicists unveil new form of matter—time crystals

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23 comments

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dirk_bruere
3 / 5 (1) Feb 22, 2017
Somehow, I suspect that if the name "Time Crystals" had been replaced with "Zero Point Energy Repetitive Fluctuation Structures" far fewer people would have heard about it.
swordsman
not rated yet Feb 22, 2017
The intra-atomic forces between atoms in a crystal are highly complex, resulting in complex reactions. They are attracted to one another by the equivalent of multiple "springs", compression and expansion. For the larger atoms, such crystals experience complex oscillations due to these "springs".Some of these oscillations are of the longer wavelengths and can be manipulated by electromagnetic field waves of similar wavelength. This reasoning is based on the electromagnetic model of the atom, first pioneered by Max Planck. Good experiment!
4cingo
not rated yet Feb 22, 2017
All that is being observed is that space-time i 3 dimensional and time is non-linear and a quanta also an elementary particle and part of space and the Quantum Field. Time is actually The Original Particle of this Multiverse and always wavering in constant flux with no end and no beginning as the Multiverse expands and contracts and the described qualities are shifting with the actions of the observer. Not at all a discovery just an observation.
4cingo
Feb 22, 2017
This comment has been removed by a moderator.
4cingo
Feb 22, 2017
This comment has been removed by a moderator.
4cingo
Feb 22, 2017
This comment has been removed by a moderator.
4cingo
Feb 22, 2017
This comment has been removed by a moderator.
Whydening Gyre
5 / 5 (5) Feb 23, 2017
All that is being observed is that space-time i 3 dimensional and time is non-linear and a quanta also an elementary particle and part of space and the Quantum Field. Time is actually The Original Particle of this Multiverse and always wavering in constant flux with no end and no beginning as the Multiverse expands and contracts and the described qualities are shifting with the actions of the observer. Not at all a discovery just an observation.

Ok... we got it. Time is a result of space adding to itself non linearly, due to addition of a spin axis. 5 repititions wasn't necessary...
physman
5 / 5 (2) Feb 23, 2017
I guess you could say that 4cingo's post has Zero Point, Energy, and Repetitive Fluctuation Structures
4cingo
not rated yet Feb 23, 2017
We are seeing time as a crystal maybe as a result of using a 4 dimensional space-time configuration to observe a 3 dimensional system and so by adding a line the observer is making the rotation of the time particles angular ? Zero point energy and maximum potential in the quantum field are the same the observations establish a specific condition of it. Apologies my thumb got stuck clicking .
antialias_physorg
5 / 5 (4) Feb 23, 2017
We are seeing time as a crystal

This isn't about time.
This is aboout materials with (endlessly) repating state transitions. No one is seeing 'time as a crystal'. Try reading the article first.
SiaoX
not rated yet Feb 26, 2017
Perpetual motion machines, which are machines that can work indefinitely without an energy source, are forbidden by the laws of physics
But the time crystals don't do any work - they're just movin' in similar way, like the planets revolve the Sun and no physical law prohibits such a motion. Once we'll try to suck an energy from time crystal, we will destroy it: we would broke its periodicity.
savvys84
not rated yet Feb 27, 2017
new state of matter can also be produced, when you start removing the time dimension from a material
manfredparticleboard
2 / 5 (4) Feb 27, 2017
If you remove time from matter you end up in a black hole, if time dilates to the point where no exchange particle can ever reach its' destination, then any quantum event becomes a singular entity and no longer interacts with anything else. There's no force, no charge, no mass; the discreet structure to a particle, subatomic or smaller becomes meaningless. How this leaves such intense curvature to spacetime is a mystery, mass can no longer inform the rest of space it exists or existed beyond the event horizon. Unless information is conserved? ....damn you Hawking... right again.
savvys84
1 / 5 (2) Feb 28, 2017
If you remove time from matter you end up in a black hole, if time dilates to the point where no exchange particle can ever reach its' destination, then any quantum event becomes a singular entity and no longer interacts with anything else. There's no force, no charge, no mass; the discreet structure to a particle, subatomic or smaller becomes meaningless. How this leaves such intense curvature to spacetime is a mystery, mass can no longer inform the rest of space it exists or existed beyond the event horizon. Unless information is conserved? ....damn you Hawking... right again.

actually the reverse. Einstein and hawking are wrong.
chk out https://www.scrib...savvys84
manfredparticleboard
2 / 5 (4) Feb 28, 2017
Funny how a theory debunking time dilation based on personal observation of fireworks, aircraft strobe lights and candles has not somehow garnered wide spread support by the wider scientific community? If I could I'd pat you on the head and say 'Nice try...now run along and play with the other kids"
antialias_physorg
5 / 5 (1) Feb 28, 2017
when you start removing the time dimension from a material

This makes no sense. We live in spacetime. You cannot 'remove time' (just like you cannot remove 'width' or 'length' from a material). There's a reason why it's called spacetime and not space-and-time.
manfredparticleboard
2 / 5 (4) Feb 28, 2017

This makes no sense. We live in spacetime..

kind of a killer argument right there.
savvys84
not rated yet Mar 01, 2017
Funny how a theory debunking time dilation based on personal observation of fireworks, aircraft strobe lights and candles has not somehow garnered wide spread support by the wider scientific community? If I could I'd pat you on the head and say 'Nice try...now run along and play with the other kids"
Nice try, but your point is moot im afraid
All relevant facts my friend and besides there are 3 papers there. try all 3
savvys84
not rated yet Mar 01, 2017
when you start removing the time dimension from a material

This makes no sense. We live in spacetime. You cannot 'remove time' (just like you cannot remove 'width' or 'length' from a material). There's a reason why it's called spacetime and not space-and-time.

yes you can remove time.
did you not read the link?My word people on here are just trigger happy to post without trying to understand and they are getting a 5/5 rating
savvys84
not rated yet Mar 01, 2017

This makes no sense. We live in spacetime..

kind of a killer argument right there.

oh really. you all need to gear up for some cutting edge physics
manfredparticleboard
1 / 5 (3) Mar 01, 2017

All relevant facts my friend and besides there are 3 papers there. try all 3


Actually we did, when you gave support to the last kook who demanded Einstein be removed from all physics references, when he'd misinterpreted a line of reasoning in an early GR paper.
After I read them I thought if you get Aditya Roy Kapur and Naseeruddin Shar to sing the lead roles I'll get the funding to make the movie.
savvys84
not rated yet Mar 02, 2017

All relevant facts my friend and besides there are 3 papers there. try all 3


Actually we did, when you gave support to the last kook who demanded Einstein be removed from all physics references, when he'd misinterpreted a line of reasoning in an early GR paper.
After I read them I thought if you get Aditya Roy Kapur and Naseeruddin Shar to sing the lead roles I'll get the funding to make the movie.

Lol. Then , You didnt understand jack squat did you? All papers corroborate each other. NIST Lab Expt, pl read it carefully.
Good idea about the movie tho. I'll consider it

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