A clock that will last forever: Researchers propose a way to build the first space-time crystal

Sep 24, 2012 by Lynn Yarris
A clock that will last forever
This proposed space-time crystal shows (a) periodic structures in both space and time with (b) ultracold ions rotating in one direction even at the lowest energy state. Credit: Xiang Zhang group, Berkeley Lab-UC Berkeley

(Phys.org)—Imagine a clock that will keep perfect time forever, even after the heat-death of the universe. This is the "wow" factor behind a device known as a "space-time crystal," a four-dimensional crystal that has periodic structure in time as well as space. However, there are also practical and important scientific reasons for constructing a space-time crystal. With such a 4D crystal, scientists would have a new and more effective means by which to study how complex physical properties and behaviors emerge from the collective interactions of large numbers of individual particles, the so-called many-body problem of physics. A space-time crystal could also be used to study phenomena in the quantum world, such as entanglement, in which an action on one particle impacts another particle even if the two particles are separated by vast distances.

A space-time crystal, however, has only existed as a concept in the minds of theoretical scientists with no serious idea as to how to actually build one – until now. An international team of scientists led by researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) has proposed the experimental design of a space-time crystal based on an electric-field ion trap and the Coulomb repulsion of particles that carry the same electrical charge.

"The electric field of the ion trap holds charged particles in place and Coulomb repulsion causes them to spontaneously form a spatial ring crystal," says Xiang Zhang, a faculty scientist with Berkeley Lab's Division who led this research. "Under the application of a weak static magnetic field, this ring-shaped ion crystal will begin a rotation that will never stop. The persistent rotation of trapped ions produces temporal order, leading to the formation of a space-time crystal at the lowest quantum ."

Because the space-time crystal is already at its lowest quantum energy state, its temporal order – or timekeeping – will theoretically persist even after the rest of our universe reaches entropy, thermodynamic equilibrium or "heat-death."

Zhang, who holds the Ernest S. Kuh Endowed Chair Professor of Mechanical Engineering at the University of California (UC) Berkeley, where he also directs the Nano-scale Science and Engineering Center, is the corresponding author of a paper describing this work in Physical Review Letters (PRL). The paper is titled "Space-time crystals of trapped ions." Co-authoring this paper were Tongcang Li, Zhe-Xuan Gong, Zhang-Qi Yin, Haitao Quan, Xiaobo Yin, Peng Zhang and Luming Duan.

The concept of a crystal that has discrete order in time was proposed earlier this year by Frank Wilczek, the Nobel-prize winning physicist at the Massachusetts Institute of Technology.

While Wilczek mathematically proved that a time crystal can exist, how to physically realize such a time crystal was unclear. Zhang and his group, who have been working on issues with temporal order in a different system since September 2011, have come up with an experimental design to build a crystal that is discrete both in space and time – a space-time crystal. Papers on both of these proposals appear in the same issue of PRL (September 24, 2012).

Traditional crystals are 3D solid structures made up of atoms or molecules bonded together in an orderly and repeating pattern. Common examples are ice, salt and snowflakes. Crystallization takes place when heat is removed from a molecular system until it reaches its lower energy state. At a certain point of lower energy, continuous spatial symmetry breaks down and the crystal assumes discrete symmetry, meaning that instead of the structure being the same in all directions, it is the same in only a few directions.

"Great progress has been made over the last few decades in exploring the exciting physics of low-dimensional crystalline materials such as two-dimensional graphene, one-dimensional nanotubes, and zero-dimensional buckyballs," says Tongcang Li, lead author of the PRL paper and a post-doc in Zhang's research group. "The idea of creating a crystal with dimensions higher than that of conventional 3D crystals is an important conceptual breakthrough in physics and it is very exciting for us to be the first to devise a way to realize a space-time crystal."

Just as a 3D crystal is configured at the lowest quantum energy state when continuous spatial symmetry is broken into discrete symmetry, so too is symmetry breaking expected to configure the temporal component of the space-time crystal. Under the scheme devised by Zhang and Li and their colleagues, a spatial ring of trapped ions in persistent rotation will periodically reproduce itself in time, forming a temporal analog of an ordinary spatial crystal. With a periodic structure in both space and time, the result is a space-time crystal.

"While a space-time crystal looks like a perpetual motion machine and may seem implausible at first glance," Li says, "keep in mind that a superconductor or even a normal metal ring can support persistent electron currents in its quantum ground state under the right conditions. Of course, electrons in a metal lack spatial order and therefore can't be used to make a space-time crystal."

Li is quick to point out that their proposed space-time crystal is not a perpetual motion machine because being at the lowest state, there is no energy output. However, there are a great many scientific studies for which a space-time crystal would be invaluable.

"The space-time crystal would be a many-body system in and of itself," Li says. "As such, it could provide us with a new way to explore classic many-body questions physics question. For example, how does a space-time crystal emerge? How does time translation symmetry break? What are the quasi-particles in space-time crystals? What are the effects of defects on space-time crystals? Studying such questions will significantly advance our understanding of nature."

Peng Zhang, another co-author and member of Zhang's research group, notes that a space-time crystal might also be used to store and transfer quantum information across different rotational states in both space and time. Space-time crystals may also find analogues in other physical systems beyond trapped ions.

"These analogs could open doors to fundamentally new technologies and devices for variety of applications," he says.

Xiang Zhang believes that it might even be possible now to make a space-time crystal using their scheme and state of the art ion traps. He and his group are actively seeking collaborators with the proper ion-trapping facilities and expertise.

"The main challenge will be to cool an ion ring to its ground state," Xiang Zhang says. "This can be overcome in the near future with the development of technologies. As there has never been a space-time crystal before, most of its properties will be unknown and we will have to study them. Such studies should deepen our understandings of phase transitions and symmetry breaking."

Explore further: Discovery sheds light on nuclear reactor fuel behavior during a severe event

More information: A copy of paper "Space-time crystals of trapped ions" can be read here.

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TheGhostofOtto1923
1.6 / 5 (13) Sep 24, 2012
A clock that will last forever

-I feel a desire to smash it. Eternity cannot survive intelligence.
hemitite
5 / 5 (5) Sep 24, 2012
Well as long as no one unplugs the freezer...

As for possible applications, how about a gravity wave detector?
I suppose it would have to be on the large side, but maybe not if one could use a series of them on an axis and detect space-time distortions propagating down the string. The perfect time keeping should be altered by such a wave.
hemitite
1 / 5 (1) Sep 24, 2012

"-I feel a desire to smash it. Eternity cannot survive intelligence."

Perhaps you could investigate the God hypothesis.
jscroft
2 / 5 (3) Sep 24, 2012
What happens when you observe it? Seems that would affect things somehow.
_ucci_oo
4 / 5 (4) Sep 24, 2012
All this and a couple billion bucks will get you nothing.
Tachyon8491
3.3 / 5 (7) Sep 24, 2012
Hmmm... with the addition of a digital display this could make a really snazzy egg-timer.
Lurker2358
1 / 5 (4) Sep 24, 2012
Perpetual motion machine of the 5th kind.
Silverhill
not rated yet Sep 24, 2012
5th kind? I'm aware of three kinds, the latter of which seems to be the case here. See:
http://en.wikiped...fication
UberGoober
2 / 5 (4) Sep 25, 2012
Flux capacitor!
ritwik
2.3 / 5 (3) Sep 25, 2012
IMMORTALITY !!!!!WORK ON IT, REST ALL ARE FUTILE
Hesca419
2.5 / 5 (2) Sep 25, 2012
It seems as though matter is constantly rearranging to find its lowest-energy state. If this is the ultimate sweet spot, shouldn't we have observed it somewhere by now? Shouldn't it be practically everywhere?

Eh, who knows? Maybe it will be in a couple of trillion years.
Caliban
2.3 / 5 (3) Sep 25, 2012
A clock that will last forever

-I feel a desire to smash it. Eternity cannot survive intelligence.


Agreed, otto--

Let's at least give the next universe a chance to start with a clean slate.

trekgeek1
4.3 / 5 (6) Sep 25, 2012

"-I feel a desire to smash it. Eternity cannot survive intelligence."

Perhaps you could investigate the God hypothesis.


...I had no need of that hypothesis.
-Laplace
Infiniteloop
3 / 5 (4) Sep 25, 2012
What a concept!
I think I'll put on some Pink Floyd and read that again ..
'... Ticking away the moments that make up a dull day ... You fritter and waste the hours in an offhand way ..'
unknownorgin
1 / 5 (3) Sep 25, 2012
The cost of building this would be huge. If just one atom in the housing is an isotope it can send a charged particle that could knock an electron off the crystal and it will collapse so a mass spectrograph type seperator will have to be used to gather stable atoms and then what about contamination when constucting the device and shielding from cosmic rays and background radiation?
unknownorgin
1 / 5 (3) Sep 25, 2012
Time slows down for an object in motion relative to the observer, it will not reproduce itself in time.
kochevnik
1.7 / 5 (6) Sep 25, 2012
Time is only employed by inferior beings that must use kinematics like m/s*2 so as to understand the higher dimensional space in which they are embedded. If they are seven dimensional there will be no need for a mental construct as time. If a clock is built in seven dimensions it will run in one eternal moment and never need rewinding.
Hakan1997
5 / 5 (1) Sep 25, 2012
To be able to use such a cool name "space-time crystal" in your research is a guaranteed success for raising money to build one.

Space-time crystal...just taste it...we want to build a space-time crystal that lasts for an eternity
antialias_physorg
5 / 5 (5) Sep 25, 2012
I'm not sure this clock will run until heat death. It is comprised of atoms, and it isn't yet fully certain that protons are absolutely stable.
If a proton turns out to have a half life then this will fail long before the universe 'ends'. (Though in that case 'long before' still means it will last orders of magnitude beyond the current age of the universe.)
RobL
not rated yet Sep 25, 2012
GPS system will get really precise.
Mike_Massen
1 / 5 (3) Sep 25, 2012
How to make sure it wont last forever, get it built by a government committee and have it dependent on some pc operating system ;-)

Here is article re Protons and decay:-
http://en.wikiped...on_decay

more or less, cant be bothered checking how many birthdays that is though...
Aryeh_Z
not rated yet Sep 25, 2012
The ideal place to build this is the International Space Station. Micro gravity, and access to near absolute zero for free.
Tausch
1 / 5 (2) Sep 25, 2012
The Discrete emerges from the Continuum.
Between the two is a concept, a contruct labeled clock.
O.k.
Tausch
3.3 / 5 (7) Sep 25, 2012
lite
Your fixation towards me is not healthy.
Learn to live without fixation.
(lite ranks without comment or feedback)
TheGhostofOtto1923
2 / 5 (8) Sep 25, 2012

"-I feel a desire to smash it. Eternity cannot survive intelligence."

Perhaps you could investigate the God hypothesis.
That has already been smashed. We need to inform the world about it.
ant_oacute_nio354
1 / 5 (5) Sep 25, 2012
Spacetime doesn't exist!

Antonio Saaraiva
ant_oacute_nio354
1 / 5 (6) Sep 25, 2012
Spacetime doesn't exist!

Antonio Saraiva
jackjump
3 / 5 (6) Sep 25, 2012
When the little hand is on infinity and the big hand on a quarter past infinity, what time is it?
chardo137
3 / 5 (2) Sep 25, 2012
How is a Buckyball not 3 dimensional? An Electron may be 0 dimensional (ignoring string theory), but a buckyball is a 3 dimensional array of carbon atoms, the carbon atoms themselves 3 dimensional arrays if protons, neutrons and electrons (ignoring the fundamental interaction bosons and the substructure of the nucleons). Is there some concept that I am missing?
antialias_physorg
4.5 / 5 (4) Sep 25, 2012
Is there some concept that I am missing?

Yes. The time-aspect here is an expression of the symmetries involved.

In an ordinary crsytal atoms are arranged in a 3D (or for stuff like graphene a 2D) symmetrical structure. But in those the atoms are static (i.e. you have a symmetry with respect to certain space-like intervals).

What they describe here is a system where atoms (or ions to be more precise) are in motion - however with a fixed distance to each other and a fixed periodicity (thus it's a 'time-like' crystal, as it's symmetrical with respect to certain time intervals).

This has nothing to do with a 4D structure.
Mastoras
5 / 5 (1) Sep 25, 2012
So, it is really a ring of ions, which periodically takes a series of spatial positions, then comes back to the initial position. But instead of saying that it spins around, we call it a space-time crystall. Am I right in my understanding?
Torbjorn_Larsson_OM
1 / 5 (1) Sep 25, 2012
The standard cosmology is an inflationary cosmology and such will naturally not experience heat death. They will eventually transit towards lower vacuum energy.

In other words, a spacetime crystal may be the lowest energy state of a periodic system, but only the (uninhabitable) dominant vacuum of an inflationary cosmology is the lowest energy state of a multiverse system.
antialias_physorg
not rated yet Sep 25, 2012
So, it is really a ring of ions, which periodically takes a series of spatial positions, then comes back to the initial position.

Sort of. With the added feature that they are always in the same geometric position with relation to their neighbors (not just periodically).
Mastoras
not rated yet Sep 25, 2012
@antialias_physorg
Thanks for the answer.

And I've noticed, in one of your previous messages, the reference that they are also "symmetrical in time" --if I recall the wording. So, I suppose, the term crystal is a clever way to describe it in a compact way. Well, it does give a sci-fi sense, though.
chardo137
3.7 / 5 (3) Sep 25, 2012
I do not have a problem with the concept of a 4 dimensional space-time crystal. However, in the article it said:
"Great progress has been made over the last few decades in exploring the exciting physics of low-dimensional crystalline materials such as two-dimensional graphene, one-dimensional nanotubes, and zero-dimensional buckyballs," says Tongcang Li, lead author of the PRL paper and a post-doc in Zhang's research group.
I have a problem with the description of buckyballs as zero-dimensional.
Mr Som-o
not rated yet Sep 25, 2012
By the sounds of it, this wouldn't work as an egg timer, because it only counts "up", to eternity. You need to have a little dinger-thingy to make it work. Now, that's a real challenge. Ooh! Ooh! I know, incorporate anti-seconds.
Lurker2358
3.7 / 5 (6) Sep 25, 2012
I do not have a problem with the concept of a 4 dimensional space-time crystal. However, in the article it said:
"Great progress has been made over the last few decades in exploring the exciting physics of low-dimensional crystalline materials such as two-dimensional graphene, one-dimensional nanotubes, and zero-dimensional buckyballs," says Tongcang Li, lead author of the PRL paper and a post-doc in Zhang's research group.
I have a problem with the description of buckyballs as zero-dimensional.


As do I.

Nano-tubes are actually 3-dimensional, just like a straw, and buckyballs are definitely 3-dimensional, and have even been created "containing" other atoms or molecules inside the empty space they contain, which is probably not a well known fact.

Entirely incorrect choice of words.

Crucialitis
not rated yet Sep 26, 2012
So, let me get this straight: it's a crystal that changes shape over time?
Is it solid at any given moment? Is it spinning so fast that it's almost like seeing retrograde? Can I touch it or will it obliterate my hand?
rowbyme
1 / 5 (1) Sep 26, 2012
The concept of time is simply a byproduct of motion, with no actual existence of it's own.
birddoo
3.5 / 5 (2) Sep 26, 2012
The contention that this construct is "a clock that will keep perfect time forever, even after the heat-death of the universe" is unfathomable. However, reading the article and its allusion to quantum entanglement made me think that perhaps the universe that we know is entangled with one we don't know. If the one we don't know is contracting ever faster, maybe that could explain why our universe is expanding ever faster. Suppose there is some point where the one we don't know can contract no more, then ours will cease to expand. At that point, perhaps the one we don't know transitions to a big bang expansion phase and ours embarks into a contraction phase.
antialias_physorg
not rated yet Sep 26, 2012
The contention that this construct is "a clock that will keep perfect time forever, even after the heat-death of the universe" is unfathomable.

Why is that unfathomable. all it says is that such a clock is in an energy state that is the lowest possible (i.e. it cannot 'decay' into a lower state)
rupri
not rated yet Sep 26, 2012
Obviously like so many others I was grabbed by this title, that being said I have to say it scares me.
ValeriaT
1 / 5 (2) Sep 26, 2012
The electrons are known to rotate around tiny metallic rings 4ever. IMO it's the same device.
birddoo
3 / 5 (2) Sep 27, 2012
The contention that this construct is "a clock that will keep perfect time forever, even after the heat-death of the universe" is unfathomable.

Why is that unfathomable. all it says is that such a clock is in an energy state that is the lowest possible (i.e. it cannot 'decay' into a lower state)


It is unfathomable because it is based on false premises, i.e., the concept of "forever" and the "heat-death" of the universe. Can there truly by heat-death if mass exists in a low energy state? Doesn't heat-death imply zero energy at which point there would also be zero mass. I can conceive of "forever" only under such circumstances.
Silverhill
5 / 5 (3) Sep 27, 2012
The heat death does not mean the loss of all energy -- it means the loss of (accessible, usable) energy *differences* due to randomization and dissipation. Without differences in energy concentration, work cannot be done even if much energy actually exists.
Nathan_Henry
not rated yet Sep 28, 2012
with this one could measure temporal drift
antialias_physorg
5 / 5 (3) Sep 28, 2012
I can conceive of "forever" only under such circumstances.

As Silverhill explained - heat death doesn't mean zero energy content (only zero energy potential). The energy content of the universe is constant and will be so even after heat death.

The 'forever' part is actually the 'wrong' part in the sentence, as the definition of time is dependent on a gradient of entropic change. When heat death is attained that gradient has become zero.

So 'from that point on' there is actually no meaningful definition of time anymore.
Digi
3 / 5 (2) Sep 28, 2012
It won't be forever if the universe ends in the 'Big Rip', even the trapped ions will be torn apart.
Tachyon8491
1 / 5 (2) Sep 28, 2012
I well understand heat death as predicted by the second law of T, but wonder then, about ZPE - is the 10^104 J/cm^3 no longer available to the organising principles of negentropic processes? I always had a problem with seeing "life" as just being a "closed system" and wonder about negentropic dynamics which appear to have been active in the very arising of complexity itself. Ideas?
antialias_physorg
1 / 5 (1) Sep 28, 2012
It won't be forever if the universe ends in the 'Big Rip', even the trapped ions will be torn apart.

The big rip does not imply that atoms will be torn apart. Space moves apart, but the properties of the nucleons and electrons are quantized (so they cannot 'drift apart' slowly).
The universe gets bigger. The distance between atoms in a molecule and between subatomic particles within one atom does not.
Digi
5 / 5 (1) Sep 28, 2012

The big rip does not imply that atoms will be torn apart. Space moves apart, but the properties of the nucleons and electrons are quantized (so they cannot 'drift apart' slowly).
The universe gets bigger. The distance between atoms in a molecule and between subatomic particles within one atom does not.


According to the hypothesis in Wiki, if the Big Rip occurred (and that is a big IF) even the atoms would be torn apart at the end.
antialias_physorg
not rated yet Sep 28, 2012
According to the hypothesis in Wiki, if the Big Rip occurred (and that is a big IF) even the atoms would be torn apart at the end.

You're right - my bad. I was thinking about the 'Big Freeze' scenario.
chardo137
1 / 5 (1) Sep 28, 2012
I can conceive of "forever" only under such circumstances.

As Silverhill explained - heat death doesn't mean zero energy content (only zero energy potential). The energy content of the universe is constant and will be so even after heat death.

The 'forever' part is actually the 'wrong' part in the sentence, as the definition of time is dependent on a gradient of entropic change. When heat death is attained that gradient has become zero.

So 'from that point on' there is actually no meaningful definition of time anymore.

I am not sure that we really have a meaningful definition of time now.
antialias_physorg
5 / 5 (1) Sep 28, 2012
I am not sure that we really have a meaningful definition of time now.

From two macroscopic snapshots of a scene you can deduce (not absolutely, but with great certainty) the sequence of events. If in the first scene the egg is on the table and in the next scene it's smashed on the floor you can order that sequence.

But after heat death that is no longer possible. Any two snapshots of an area of space cannot be ordered into a before/after sequence with any kind of certainty.
(Also in the quantum world before/after sequences become iffy. The question about where QM and relatity mesh is also a question of where the notion of time becomes meaningful)
birddoo
3 / 5 (2) Sep 28, 2012

The heat death of the universe, i.e., the Big Freeze, is a contentious issue, as is the Big Rip. There is also the Big Crunch theory where the universe transitions back to a phase where it ultimately contracts to a state where it is infinitesimally small which could serve as a prelude for another Big Bang. All of these theories suffer from inadequacies.
SteveL
not rated yet Sep 30, 2012
Flux capacitor!
Is a magnet.
Lex Talonis
1 / 5 (2) Oct 01, 2012
I have a space time temporal distortion rod.

It's about 3 feet long, 1 foot wide and you send it to Uranus.
tbonefrog
not rated yet Oct 01, 2012
Pardon me if this is a dumb question: if a 4D crystal exists for all future times, would it not also have to exist in all past times? That is sort of the definition of a crystal? Or do they have to set up some tricky boundary conditions at the point in time that the crystal first exists, to simulate the past existence of the crystal?
antialias_physorg
not rated yet Oct 01, 2012
Pardon me if this is a dumb question: if a 4D crystal exists for all future times, would it not also have to exist in all past times?

No. Just like a 3D crystal need not extend through all of space.
exequus
not rated yet Oct 14, 2012
The Discrete emerges from the Continuum.
Between the two is a concept, a contruct labeled clock.
O.k.

H^o. Surely you mean 'a construct' I presume.
exequus
1 / 5 (1) Oct 14, 2012
That bit about 'zero-dimensional buckyballs' strikes me as a misnomer and logically impossible, I humbly submit that 'nonzero-dimensional' would be more relevant as it allows for an unimaginably small buckyball to still have the teensiest smidgen of mass. It's easier to grasp and digest, methinks.

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