From New Scientist
Ordinary crystals are three-dimensional objects whose atoms are arranged in regular, repeating patterns – just like table salt. They adopt this structure because it uses the lowest amount of energy possible to maintain.
Earlier this year, Frank Wilczek, a theoretical physicist at the Massachusetts Institute of Technology, speculated that a similar structure might repeat regularly in the fourth dimension – time.
Wilczek has also theorised that a working time crystal could be made into a computer, with different rotational states standing in for the 0s and 1s of a conventional computer.
The article includes a description (by Tongcang Li from the University of California, and others) of how such a time crystal could be built. Though it will be tricky because building the crystal will need temperatures close to absolute zero.
While Wilczek points out that the heat-death of the universe is, in principle, "very user friendly" for this kind of experiment because it would be cold and dark, there are other issues to consider.
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Berkeley News reports on a Jan. 18th paper about time crystals:
If crystals have an atomic structure that repeats in space, like the carbon lattice of a diamond, why can't crystals also have a structure that repeats in time? That is, a time crystal? In a paper published online last week in the journal Physical Review Letters, the UC Berkeley assistant professor of physics describes exactly how to make and measure the properties of such a crystal, and even predicts what the various phases surrounding the time crystal should be — akin to the liquid and gas phases of ice.
This is not mere speculation. Two groups followed [Norman] Yao's blueprint and have already created the first-ever time crystals. The groups at the University of Maryland and Harvard University reported their successes, using two totally different setups, in papers posted online last year, and have submitted the results for publication. Yao is a co-author on both papers.
Time crystals repeat in time because they are kicked periodically, sort of like tapping Jell-O repeatedly to get it to jiggle, Yao said. The big breakthrough, he argues, is less that these particular crystals repeat in time than that they are the first of a large class of new materials that are intrinsically out of equilibrium, unable to settle down to the motionless equilibrium of, for example, a diamond or ruby. "This is a new phase of matter, period, but it is also really cool because it is one of the first examples of non-equilibrium matter," Yao said. "For the last half-century, we have been exploring equilibrium matter, like metals and insulators. We are just now starting to explore a whole new landscape of non-equilibrium matter."
Discrete Time Crystals: Rigidity, Criticality, and Realizations (DOI: 10.1103/PhysRevLett.118.030401) (DX)
Viewpoint: How to Create a Time Crystal
Observation of a Discrete Time Crystal
Previously:
Blueprint for a Time Crystal
Time Crystals Might Exist After All
(Score: 4, Interesting) by cosurgi on Monday July 06 2015, @07:37PM
I'm reading the full paper now, you can enjoy it too since library genesis isn't closed yet [soylentnews.org]. Just go there, click "Scientific articles" and search for "Quantum time crystals". I won't post the link here to avoid making troubles for our site. You have to figure it out yourself.
The paper is very interesting. Though not completely clear.
1. I am not sure how to understand "multivalued" in 2nd paragraph on 2nd page: "since fi, acting on wave functions in Hilbert space, is multivalued". I know what "multivalued" means, I have just never encountered such a beast (as Wilczek calls it "non-legitimate operator") in QM.
2. I am not sure if delta in Eq.13 is a Dirac's delta or just a symbol for the potential. (I assume it's Dirac's delta).
Apart from that I see that comprehending this paper a bit more would take me about two weeks :) Too bad I'm in hurry now, but hopefully will get back to it later.
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#\ @ ? [adom.de] Colonize Mars [kozicki.pl]
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(Score: 4, Informative) by boristhespider on Monday July 06 2015, @08:23PM
Nothing dubious needed. It's worth noting that the NS article is from 2012, so the "earlier this year" is a bit misleading from a 2015 perspective.
http://arxiv.org/abs/1202.2537 [arxiv.org] "Classical Time Crystals", Shapere and Wilczek
http://arxiv.org/abs/1202.2539, [arxiv.org] "Quantum Time Crystals", Wilczek (the paper you're referring to)
http://arxiv.org/abs/1206.4772, [arxiv.org] "Space-time crystals of trapped ions", Li et al (the other paper referred to in the article)
(Score: 2) by cosurgi on Monday July 06 2015, @09:04PM
Thanks!
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#\ @ ? [adom.de] Colonize Mars [kozicki.pl]
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(Score: 0) by Anonymous Coward on Monday July 06 2015, @09:53PM
No problem. Also that's definitely a Dirac delta in the potential. I only skimmed it but from what he said about phidot, I'd suspect that phi is "multivalued" in the sense that it has multiple branches. But as I say I'd have to read it and quantum mechanics (or field theory, come to that) is very far from my field.
(Score: 2) by boristhespider on Monday July 06 2015, @09:54PM
Sorry, that was me. Posted via my work machine which I don't use logins (other than email) on.
(Score: 4, Insightful) by frojack on Monday July 06 2015, @10:42PM
I'm reading the full paper now, you can enjoy it too since library genesis isn't closed yet [soylentnews.org]. Just go there, click "Scientific articles" and search for "Quantum time crystals". I won't post the link here to avoid making troubles for our site. You have to figure it out yourself.
Translation: I'm too lazy to post a link of the page I have up in my other browser window.
No, you are mistaken. I've always had this sig.
(Score: 2) by cosurgi on Tuesday July 07 2015, @10:54AM
Not really, maybe I'm weird, but I was trying to play it safe :)
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#\ @ ? [adom.de] Colonize Mars [kozicki.pl]
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(Score: 4, Funny) by TrumpetPower! on Monday July 06 2015, @08:32PM
Unless I'm quite mistraken, we've been here before [timecube.com]....
b&
All but God can prove this sentence true.
(Score: 1) by meustrus on Monday July 06 2015, @09:47PM
Very confused as that web site 1) seems to no longer exist, and 2) on the Wayback Machine points to some large-font obnoxious junk about 1 minute being 1 minute because God? What are you trying to show us?
If there isn't at least one reference or primary source, it's not +1 Informative. Maybe the underused +1 Interesting?
(Score: 0) by Anonymous Coward on Monday July 06 2015, @11:05PM
Very confused? That's timecube for ya.
The website does exist, though - I just loaded it to check.
(Score: 1) by FrogBlast on Monday July 06 2015, @11:45PM
I just had it load, then get replaced half a second later with a sketchy search page. I'm as enamored of 4 Corner Days as the next man, but something is definitely amiss over there.
(Score: 2) by The Archon V2.0 on Tuesday July 07 2015, @01:16PM
> I'm as enamored of 4 Corner Days as the next man, but something is definitely amiss over there.
More than usual, anyway.
(Score: 4, Insightful) by dbe on Monday July 06 2015, @10:29PM
So for the layman, would these crystal be a structure that would change over time and their geometry would periodically go back to the same shape?
In is a sense would be analog to gliders structures in the game of life?
https://en.wikipedia.org/wiki/Glider_(Conway's_Life) [wikipedia.org]
-dbe
(Score: 2) by Kell on Tuesday July 07 2015, @02:03AM
Regularly repeating configuration in time? It does sound suspiciously like an oscillator.
Scientists ask questions. Engineers solve problems.
(Score: 3, Insightful) by boristhespider on Tuesday July 07 2015, @07:16AM
Yes - but they're in their lowest energy state. An oscillator will be driven, and then decay through friction etc when the driving force is removed. These are structures who exhibit motion in their "rest" state. Phrased slightly differently, they identify spatial crystals by a symmetry breaking - the equations of motion have greater symmetry than the solution. For a classical crystal, for instance, the equations of motion have translational symmetry but the crystal definitely doesn't.
In the first paper ("Classical Time Crystals") they point out, "This seems perilously close to perpetual motion". Wilczek went to supercold regimes because it's reminiscent of superfluidity. In a quantum system you can conceivably get this kind of effect - you're free from thermal noise and you can build a system with large scale coherence.
But yes, it does sound like an oscillator. Just a particular class of one. I like the analogy with the walkers in Conway's Game of Life.
(Score: 2, Funny) by Anonymous Coward on Tuesday July 07 2015, @01:58AM
Wilczek has also theorised that a working time crystal could be made into a computer, with different rotational states standing in for the 0s and 1s of a conventional computer.
And when you need a debugger you can go downtown to that Psychic's shop and buy a crystal with truth seeking properties.
(Score: 2) by captain normal on Tuesday July 07 2015, @03:50AM
Anyone else think of Superman's Crystal Palace?
When life isn't going right, go left.
(Score: 0) by Anonymous Coward on Tuesday July 07 2015, @06:18AM
Here's another article on the subject http://www.wired.com/2013/04/time-crystals/all/ [wired.com]
Theoretical physics is too funky for me. Yet undoubtedly an important field to study.