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Could someone summarize the above in the article if it's relevant? I don't understand it well enough to attempt this. Thanks. 50.0.205.96 ( talk) 23:06, 6 October 2016 (UTC)
The result of the move request was: No consensus. Sources are mixed; they use both 'time crystal' and 'space time crystal.' I suggest waiting a reasonable time. Then reconsider the move based on the predominant usage in refereed journals. If we were to go by Wilczek 2012, assuming he is the actual creator of the idea, he called them 'quantum time crystals' in the title of his published paper. EdJohnston ( talk) 19:42, 19 October 2016 (UTC)
Space-time crystal → Time crystal – Recent coverage, including coverage of claimed experimental results, seems to have settled on the name "time crystal". Examples:
As with the editors above, I don't claim to be an expert on the bleeding-edge science involved here, but these all seem to be covering the same topic as this article does. Given the current attention to this topic, our article title should match what's being used in the press. 64.105.98.115 ( talk) 17:42, 12 October 2016 (UTC)
No clear discussion of 2nd law here. It is needed. — Preceding unsigned comment added by 123.3.154.75 ( talk) 05:25, 29 January 2017 (UTC)
Here's a 2021 quote:
This quote would also seem to contradict the current statement in the Thermodynamics section "Time crystals do not violate the laws of thermodynamics." I'm not an expert in the scientific meanings of the words "evade" and "violate" so I will leave the argument to others. 5Q5| ✉ 10:56, 2 August 2021 (UTC)
https://bigthink.com/starts-with-a-bang/time-crystal/
-- AloisIrlmaier ( talk) 05:56, 14 October 2021 (UTC)
The article has been changed to have an extremely complex referencing format. This is now so complex that readers will likely not bother to use it. Readers click through to a note that can have 4 clickable links in it. These links then can go to a citations section. Then they have to click on a Harvard format reference to get to an entry in one of three following sections. This is non standard for Wikipedia and is very complex for readers or editors. Few editors will be able to maintain this. This is not a textbook but an encyclopedia article mostly read on online devices. I propose this should be much simplified. The Notes section should only be for textual notes: currently q, ae, ag, ah. The other entries prefixed with "see" become regular references. For the other references, clicking on their footnote should go directly to a references section with entries as in the academic papers section. The section labelled "citations" should be scrapped. Entries in academic, Papers, and Books that are not used as references in-line can become entries in an "Extra reading" (or External links) section
Need someone to write the "Simple English" article ASAP. SammyMajed ( talk) 09:00, 10 March 2017 (UTC)
In plain English the opening paragraph could be made quite simple: For example: A time crystal refers to a crystal who's structure is not rigid but rather in perpetual motion. The perpetual motion is achieved by continuously imparting energy into the crystal from an external source to get it out of its zero energy ground state. The perpetual motion moves in a specific pattern that repeats itself over and over again. The movement is thought to cause a phenomenon called quantum entanglement between the particles of the crystal. This entanglement makes the crystal impervious over time to outside forces that would normally breakdown a rigid crystal structure. This breakdown by outside forces is called quantum decoherence by physicists. Essentially the crystal remains forever young and will not lose any information encoded within it. This is a property highly sought after by engineers who are designing quantum computers. Gaurus ( talk) 19:22, 3 May 2017 (UTC)
With this request I would like to reopen the so-called "Requested move 12 October 2016" issue. With the latest scientific issues published, the scientific community starts to use the term Time-Crystal more and more exclusively, henceforth this article should follow suit and refect the census of the scientific community. [1] [2] [3] [4] [5] [6] [7]
It is no longer a question if 'every researcher want's to have their own name', it has become common treatment, and thus is no longer a moot question iof personal preference. Asragin 2A02:8071:2388:8300:E1E9:62E:7173:1426 ( talk) 08:45, 13 March 2017 (UTC)
Yeah the peak in April 2009 from the above seems to be from "Final Fantasy Crystal Chronicles: Echoes of Time" I don't think a query without quotes is going give you any indication of the proportion true volume on the topic of time crystals vs space-time crystal. I've changed the name of the article since no-one seems to oppose.-- Sparkyscience ( talk) 09:37, 14 March 2017 (UTC)
References
At no place I can find the abbreviation "MBL" defined either in the graphic or the article, nor is it listed as anything relevant in Wikipedia in the disambiguation pages. J with a B ( talk) 06:27, 14 March 2017 (UTC)
Please define: time translation nonlocal correlation fault tolerance Quantum correlated state
Thanks — Preceding unsigned comment added by 24.224.248.82 ( talk) 14:33, 14 March 2017 (UTC)
Can the lead-in explain things for 'non-physicists/crystallographers'? 86.146.99.55 ( talk) 13:50, 15 March 2017 (UTC)
The article states "The crystal's pattern repeats not in space, but in time, which allows for the crystal to be in PERPETUAL MOTION"
But Wikipedia's own article on 'perpetual motion' states: "Perpetual motion is motion of bodies that continues indefinitely. This is IMPOSSIBLE because of friction and other energy-dissipating processes."
79.76.99.103 ( talk) 19:20, 15 March 2017 (UTC)
A quote from a member of the team who made one states “It’s not a perpetual motion machine,” Jiehang Zhang, a member of the University of Maryland team, tells Gizmodo. “We’re driving it!" unquote, so to summarize, your correct it not in perpetual motion.
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The link to "Perpetuum mobile" links to a music reference instead of to the physics perpetual motion page: /info/en/?search=Perpetual_motion Samuel Thornkey ( talk) 00:41, 16 March 2017 (UTC)
chronocrystal (χρόνος + κρύσταλλο[ς]) — Preceding unsigned comment added by 2A02:587:4100:9F00:71BD:A55E:8466:CC77 ( talk) 07:22, 16 March 2017 (UTC)
It feels as if the sentence and ensuing paragraphs, which begin: "In 2016, Norman Yao and his colleagues from the University of California, Berkeley, put forward a concrete proposal that", belongs in the article and not in the Lede. Suggest moving or condensing those paragraphs into the history section and using the Lede for a more pedestrian explanation of the subject so as to remove the "too technical" tag. Edaham ( talk) 09:22, 16 March 2017 (UTC)
The History section currently reads: "..misunderstanding the orginal Wilczek paper or, requiring the true ground state i.e. the lowest energy eigenstate of the Hamiltonian to have the perpetual motion that trivially, is impossible because the motion must mean the superposition."
"Hamiltonian" needs further clarification - maybe just a link (presumably to Hamiltonian (quantum mechanics)?) will do. Oh!, and "orginal" should be "original". 199.200.27.9 ( talk) 19:36, 16 March 2017 (UTC)
I'm a layperson, albeit one that enjoys reading about and exploring complex scientific topics, such as this. However, this article fails to convey to me a coherent sense of what the topic is. A starting point might be a comparison with ordinary crystals and how these are different.
Informata ob Iniquitatum (
talk)
02:00, 19 April 2017 (UTC)
I've rewritten the lede to hopeful clarify a few things. I will remove the too technical tag, but please reapply if the lede still is not clear. If there is a specific section in the article which needs more work, apply the too technical tag there as well.-- Sparkyscience ( talk) 11:59, 4 May 2017 (UTC)
Time crystals are fascinating, but this article does not describe them well. I remember reading this article years ago when it gave a pretty concise summary of the topic; it has come far afield since then. (Was this in response to the recent experiments? Something else?)
The current article is full of misleading statements (perpetual motion), gives undue weight to tangents that are barely related to the concept (digressions on every symmetry, topological order, zero-point energy, casimir effect), and uses a confusing non-standard footnote+note scheme. Some important aspects, like the series of no-go arguments, are presented in a confusing way and without context.
I'm not sure how to improve the current state: it seems to be crafting an elaborate narrative with the topic as a starting point, which is not what an article is generally for. I'll start with the most glaring issues:
This section looks fine.
Regards, – SJ + 07:17, 1 July 2017 (UTC)
I applaud all the good work done by SJ mentioned above. However I still have a problem with one sentence:
This seems to be unsourced: the cited source ( Chernodub) is not about time crystals but about a zero-point energy system; the term "open system" does not appear in it; and the word "driven" only appears in the phrase "zero-point energy driven"; this does not refer to an external driving force. I feel this sentence is a very misleading WP:SYNTHESIS. In thermodynamics an "open system" is one that exchanges energy with its surroundings, and a "driven" system is one whose motion is caused by an external force. I agree, time crystals are not "perpetual motion machines", and do not violate the laws of thermodynamics. But the reason for this is not that they are "open" systems which are "driven" by an external energy source. The reason is that they are in their minimum energy quantum " ground state", so no energy can be extracted from them. Their "motion" does not really represent conventional kinetic energy [3]; they possess "motion without energy" [4]. I think this sentence should be rewritten. -- Chetvorno TALK 00:16, 20 September 2017 (UTC)
Now that SJ has done such a great job cleaning up the article, I think the "References" section should be cleaned up. The section has 116 sources, of which only 19 are referenced by inline citations. Without knowing which parts of the article they refer to, the rest are pretty useless. Many of them supported trivial or off-topic content such as Casimir effect which has been deleted. A few of the sources most relevant to the subject could be moved to a "Further reading" section, but the rest should be deleted. -- Chetvorno TALK 05:39, 2 September 2018 (UTC)
I agree. I will try to clean up the reference section by first omitting all the off topic ones. CA2MI ( talk) 18:01, 5 April 2021 (UTC)
A new SPA has made started making edits, [5] first at Frank Wilczek and then here, representing a 2015 paper by Oshikawa and Watanabe as "scientific consensus as of 2019." [6] The same editor removed (from FW article) the citation of a 2018 article in Physics World written by Philip Ball (which discusses the 2015 paper at some length) as "The prior edits cite popular science articles that do not reflect academic consensus." [7]
The time crystal article has been in a consensus state, so I think other editors ( @ Sj: ) should take a look at the changes I reverted before the article displays them.
Also, is the IP correct to remove the entire section on Thermodynamics? They disagree with a statement sourced to Science Alert, but other material removed was sourced to Scientific American and academic papers. Thermodynamics seems a worthwhile topic to cover, and blanking the section seems extreme.
Also we should be careful that we rely on secondary sources and RS to evaluate which concepts are of critical importance to the field. Quite a lot has happened since 2015. Perhaps published RS exist that assert the Oshikawa/Watanabe paper from 2015 represents "scientific consensus as of 2019," but until/unless we can cite such RS, the article should not be making such claims. HouseOfChange ( talk) 17:22, 26 March 2019 (UTC)
I have found a citation for the uncited assertion (which I reverted because it was uncited) that two experiments in 2016 were independent work. [1] Similarly, Philip Ball writing in Physics World emphasizes that the two experiments should be treated on an even-handed basis. [2]
IMO, the article should talk about these two experiments with a similar level of detail, and based what independent RS have said about them, not so much on the original primary sources. HouseOfChange ( talk) 16:03, 19 June 2021 (UTC)
References
Monroe, a physicist at the University of Maryland in College Park, and his team used chains of atoms they had constructed for other purposes to make a version of a time crystal...And a group led by researchers at Harvard University in Cambridge, Massachusetts, independently fashioned time crystals out of 'dirty' diamonds. Both versions, which are published this week in Nature, are considered time crystals, but not how Wilczek originally imagined...They are also the first examples of a remarkable type of matter — a collection of quantum particles that constantly changes, and never reaches a steady state.
Last year Monroe and his coworkers reported the characteristic signature of a DTC in an array of 10 ytterbium ions held in a trap, where their spins interact with one another...At the same time, a team at Harvard University led by Mikhail Lukin saw another way to create a quantum system with the requisite disorder: it could come from impurities distributed randomly in a diamond crystal lattice.
Partially quoting a paper from 2012 [8] that described time crystals as "systems with time-periodic ground states that break translational time symmetry" can hardly be our best possible choice. There have now been lots of articles about time crystals, and we should search them for good ways to explain what a time crystal is. Here are some other possibilities.
I think a good clear definition will explain the analogy to crystals and say something informative about the role of symmetry breaking in their realization. What do other editors think? HouseOfChange ( talk) 01:21, 4 August 2021 (UTC)
There is a lot of recent news about time crystals but... Is there some rule of thumb we could use to decide when "this group made a 2021 discovery (link to primary research paper and to the home institution news article)" does or doesn't require a separate paragraph? When independent RS cover somebody's new experiment, we get better context of how it relates to time crystals.
Maybe there should be a separate article about time crystal experiments? Hoping for guidance from more experienced editors. HouseOfChange ( talk) 00:24, 9 August 2021 (UTC)
Wikipedia is an encyclopedia, whose articles are aimed at informing a general audience about notable topics. We rarely cite primary research papers, because topics of general interest should have been treated in an accessible way by secondary or even tertiary sources. If this article should have a section on "Condensed matter in crystalline structures in time", it needs to be a lot clearer why this improves the encyclopedia project, as opposed to why it matters to people who have published scholarly papers to see their work mentioned in Wikipedia.
Time crystalline structures can also be created externally like photonic crystals. The latter do not emerge spontaneously because periodic modulation of the refractive index in space is imposed externally. Resonant periodic driving of a single or many-body systems can reveal condensed matter-like behavior [1] [2]. For example, Anderson and many-body localization in time, topological time crystals, superfluid-Mott insulator phase transition in the time domain can be realized in resonantly driven systems [3] [4] [5], see also [6].
Here is the section I removed. If others feel it belongs in the article, how can it be improved and where should it go? HouseOfChange ( talk) 13:51, 30 August 2021 (UTC)
References
We show that an ultracold atomic cloud bouncing on an oscillating mirror can reveal spontaneous breaking of a discrete time-translation symmetry
Time crystals do not violate the laws of thermodynamics [....] Time crystals do evade the Second Law of Thermodynamics
?
IncompleteBits ( talk) 16:57, 6 November 2021 (UTC)
I reverted an extensive edit talking up the Google experiment, not least because it replaced the accurate description of Google's many collaborators coming from " multiple universities" with the inaccurate claim that all came from "Standford University" [sic]. Could other editors take a look? HouseOfChange ( talk) 20:10, 27 December 2021 (UTC)
Hello, people who know more than I do. I just watched the video at https://m.youtube.com/watch?v=ieDIpgso4no . That was my very first exposure to the term and concept covered by this article, time crystals.
In that video, the speaker says that the 2017 time crystals were not true time crystals. My impression was that they failed to fit the definition in some technical or crucial way. The speaker goes on to say that in 2021, the Google experiment produced true time crystals, and others have as well. I can't say anything about the speaker's source of information or understanding of the material (except of course that they both probably exceed my own, very greatly).
It's also worth noting that the video was posted only about 11 hours ago, so this could be new information, or relatively new, whatever. Yay for bleeding edge science!
So, I've posted this only so that better and more concerned minds can consider whether any of the article needs updating, or not. Should the description of the 2017 results be adjusted? I am not especially invested in the answer, other than the general desire to help Wikipedia be accurate. I won't be checking back, and don't have anything more to contribute to the conversation.
Thanks for all you do, people!
Signed,
Just a casual passer-by, hoping to be helpful. — Preceding unsigned comment added by 24.56.77.201 ( talk) 08:26, 16 June 2022 (UTC)
It would probably be worth including in the article, in light of the fact that our chief interest in time crystals is their apparent (though faux) violation of second law of thermodynamics, by way of perpetual motion. (I say faux because the term 'motion' is questionable in this context, given that the oscillations are trapped in the system and shouldn't be treated as 'free' energy. Actually, if we could quantify the energy that it takes to set up a time crystal, which is then converted into unavailable energy, it would have to be identical to the 'change in entropy', right? But because you're necessarily setting up a system that doesn't have any free energy, it's non-enthalpic, and therefore the net change in entropy is... zero. Augh! It breaks my understanding of thermodynamics. This could use attention from an expert). Atomic putty? Rien! 14:31, 14 September 2022 (UTC)
Currently, the article includes this paragraph:
An earlier "proof" that a time crystal cannot exist in thermal equilibrium [1] was shown to have a subtle error that renders it invalid (See Appendix A of Khemani, Moessner, and Sondhi (2019). [2]). Recent experimental advances in probing discrete time crystals in their periodically driven nonequilibrium states have led to the beginning exploration of novel phases of nonequilibrium matter. [3]
I have disputed this proposed edit, because it references primary research by involved authors rather than secondary source confirming it:
However, the proof was completed shortly after and now is thought to hold [4].
I agree that Wikivoice shouldn't say the proof was wrong if its error has since been corrected. But the primary source cited is dated 2020, plenty of time for secondary source to weigh in on one side of the other. Perhaps the entire paragraph should just be eliminated. What do others think? HouseOfChange ( talk) 23:16, 10 November 2022 (UTC) HouseOfChange ( talk) 23:16, 10 November 2022 (UTC)
References
WO 2015
was invoked but never defined (see the
help page).KMS 2019
was invoked but never defined (see the
help page).else et al 2020
was invoked but never defined (see the
help page).
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Could someone summarize the above in the article if it's relevant? I don't understand it well enough to attempt this. Thanks. 50.0.205.96 ( talk) 23:06, 6 October 2016 (UTC)
The result of the move request was: No consensus. Sources are mixed; they use both 'time crystal' and 'space time crystal.' I suggest waiting a reasonable time. Then reconsider the move based on the predominant usage in refereed journals. If we were to go by Wilczek 2012, assuming he is the actual creator of the idea, he called them 'quantum time crystals' in the title of his published paper. EdJohnston ( talk) 19:42, 19 October 2016 (UTC)
Space-time crystal → Time crystal – Recent coverage, including coverage of claimed experimental results, seems to have settled on the name "time crystal". Examples:
As with the editors above, I don't claim to be an expert on the bleeding-edge science involved here, but these all seem to be covering the same topic as this article does. Given the current attention to this topic, our article title should match what's being used in the press. 64.105.98.115 ( talk) 17:42, 12 October 2016 (UTC)
No clear discussion of 2nd law here. It is needed. — Preceding unsigned comment added by 123.3.154.75 ( talk) 05:25, 29 January 2017 (UTC)
Here's a 2021 quote:
This quote would also seem to contradict the current statement in the Thermodynamics section "Time crystals do not violate the laws of thermodynamics." I'm not an expert in the scientific meanings of the words "evade" and "violate" so I will leave the argument to others. 5Q5| ✉ 10:56, 2 August 2021 (UTC)
https://bigthink.com/starts-with-a-bang/time-crystal/
-- AloisIrlmaier ( talk) 05:56, 14 October 2021 (UTC)
The article has been changed to have an extremely complex referencing format. This is now so complex that readers will likely not bother to use it. Readers click through to a note that can have 4 clickable links in it. These links then can go to a citations section. Then they have to click on a Harvard format reference to get to an entry in one of three following sections. This is non standard for Wikipedia and is very complex for readers or editors. Few editors will be able to maintain this. This is not a textbook but an encyclopedia article mostly read on online devices. I propose this should be much simplified. The Notes section should only be for textual notes: currently q, ae, ag, ah. The other entries prefixed with "see" become regular references. For the other references, clicking on their footnote should go directly to a references section with entries as in the academic papers section. The section labelled "citations" should be scrapped. Entries in academic, Papers, and Books that are not used as references in-line can become entries in an "Extra reading" (or External links) section
Need someone to write the "Simple English" article ASAP. SammyMajed ( talk) 09:00, 10 March 2017 (UTC)
In plain English the opening paragraph could be made quite simple: For example: A time crystal refers to a crystal who's structure is not rigid but rather in perpetual motion. The perpetual motion is achieved by continuously imparting energy into the crystal from an external source to get it out of its zero energy ground state. The perpetual motion moves in a specific pattern that repeats itself over and over again. The movement is thought to cause a phenomenon called quantum entanglement between the particles of the crystal. This entanglement makes the crystal impervious over time to outside forces that would normally breakdown a rigid crystal structure. This breakdown by outside forces is called quantum decoherence by physicists. Essentially the crystal remains forever young and will not lose any information encoded within it. This is a property highly sought after by engineers who are designing quantum computers. Gaurus ( talk) 19:22, 3 May 2017 (UTC)
With this request I would like to reopen the so-called "Requested move 12 October 2016" issue. With the latest scientific issues published, the scientific community starts to use the term Time-Crystal more and more exclusively, henceforth this article should follow suit and refect the census of the scientific community. [1] [2] [3] [4] [5] [6] [7]
It is no longer a question if 'every researcher want's to have their own name', it has become common treatment, and thus is no longer a moot question iof personal preference. Asragin 2A02:8071:2388:8300:E1E9:62E:7173:1426 ( talk) 08:45, 13 March 2017 (UTC)
Yeah the peak in April 2009 from the above seems to be from "Final Fantasy Crystal Chronicles: Echoes of Time" I don't think a query without quotes is going give you any indication of the proportion true volume on the topic of time crystals vs space-time crystal. I've changed the name of the article since no-one seems to oppose.-- Sparkyscience ( talk) 09:37, 14 March 2017 (UTC)
References
At no place I can find the abbreviation "MBL" defined either in the graphic or the article, nor is it listed as anything relevant in Wikipedia in the disambiguation pages. J with a B ( talk) 06:27, 14 March 2017 (UTC)
Please define: time translation nonlocal correlation fault tolerance Quantum correlated state
Thanks — Preceding unsigned comment added by 24.224.248.82 ( talk) 14:33, 14 March 2017 (UTC)
Can the lead-in explain things for 'non-physicists/crystallographers'? 86.146.99.55 ( talk) 13:50, 15 March 2017 (UTC)
The article states "The crystal's pattern repeats not in space, but in time, which allows for the crystal to be in PERPETUAL MOTION"
But Wikipedia's own article on 'perpetual motion' states: "Perpetual motion is motion of bodies that continues indefinitely. This is IMPOSSIBLE because of friction and other energy-dissipating processes."
79.76.99.103 ( talk) 19:20, 15 March 2017 (UTC)
A quote from a member of the team who made one states “It’s not a perpetual motion machine,” Jiehang Zhang, a member of the University of Maryland team, tells Gizmodo. “We’re driving it!" unquote, so to summarize, your correct it not in perpetual motion.
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The link to "Perpetuum mobile" links to a music reference instead of to the physics perpetual motion page: /info/en/?search=Perpetual_motion Samuel Thornkey ( talk) 00:41, 16 March 2017 (UTC)
chronocrystal (χρόνος + κρύσταλλο[ς]) — Preceding unsigned comment added by 2A02:587:4100:9F00:71BD:A55E:8466:CC77 ( talk) 07:22, 16 March 2017 (UTC)
It feels as if the sentence and ensuing paragraphs, which begin: "In 2016, Norman Yao and his colleagues from the University of California, Berkeley, put forward a concrete proposal that", belongs in the article and not in the Lede. Suggest moving or condensing those paragraphs into the history section and using the Lede for a more pedestrian explanation of the subject so as to remove the "too technical" tag. Edaham ( talk) 09:22, 16 March 2017 (UTC)
The History section currently reads: "..misunderstanding the orginal Wilczek paper or, requiring the true ground state i.e. the lowest energy eigenstate of the Hamiltonian to have the perpetual motion that trivially, is impossible because the motion must mean the superposition."
"Hamiltonian" needs further clarification - maybe just a link (presumably to Hamiltonian (quantum mechanics)?) will do. Oh!, and "orginal" should be "original". 199.200.27.9 ( talk) 19:36, 16 March 2017 (UTC)
I'm a layperson, albeit one that enjoys reading about and exploring complex scientific topics, such as this. However, this article fails to convey to me a coherent sense of what the topic is. A starting point might be a comparison with ordinary crystals and how these are different.
Informata ob Iniquitatum (
talk)
02:00, 19 April 2017 (UTC)
I've rewritten the lede to hopeful clarify a few things. I will remove the too technical tag, but please reapply if the lede still is not clear. If there is a specific section in the article which needs more work, apply the too technical tag there as well.-- Sparkyscience ( talk) 11:59, 4 May 2017 (UTC)
Time crystals are fascinating, but this article does not describe them well. I remember reading this article years ago when it gave a pretty concise summary of the topic; it has come far afield since then. (Was this in response to the recent experiments? Something else?)
The current article is full of misleading statements (perpetual motion), gives undue weight to tangents that are barely related to the concept (digressions on every symmetry, topological order, zero-point energy, casimir effect), and uses a confusing non-standard footnote+note scheme. Some important aspects, like the series of no-go arguments, are presented in a confusing way and without context.
I'm not sure how to improve the current state: it seems to be crafting an elaborate narrative with the topic as a starting point, which is not what an article is generally for. I'll start with the most glaring issues:
This section looks fine.
Regards, – SJ + 07:17, 1 July 2017 (UTC)
I applaud all the good work done by SJ mentioned above. However I still have a problem with one sentence:
This seems to be unsourced: the cited source ( Chernodub) is not about time crystals but about a zero-point energy system; the term "open system" does not appear in it; and the word "driven" only appears in the phrase "zero-point energy driven"; this does not refer to an external driving force. I feel this sentence is a very misleading WP:SYNTHESIS. In thermodynamics an "open system" is one that exchanges energy with its surroundings, and a "driven" system is one whose motion is caused by an external force. I agree, time crystals are not "perpetual motion machines", and do not violate the laws of thermodynamics. But the reason for this is not that they are "open" systems which are "driven" by an external energy source. The reason is that they are in their minimum energy quantum " ground state", so no energy can be extracted from them. Their "motion" does not really represent conventional kinetic energy [3]; they possess "motion without energy" [4]. I think this sentence should be rewritten. -- Chetvorno TALK 00:16, 20 September 2017 (UTC)
Now that SJ has done such a great job cleaning up the article, I think the "References" section should be cleaned up. The section has 116 sources, of which only 19 are referenced by inline citations. Without knowing which parts of the article they refer to, the rest are pretty useless. Many of them supported trivial or off-topic content such as Casimir effect which has been deleted. A few of the sources most relevant to the subject could be moved to a "Further reading" section, but the rest should be deleted. -- Chetvorno TALK 05:39, 2 September 2018 (UTC)
I agree. I will try to clean up the reference section by first omitting all the off topic ones. CA2MI ( talk) 18:01, 5 April 2021 (UTC)
A new SPA has made started making edits, [5] first at Frank Wilczek and then here, representing a 2015 paper by Oshikawa and Watanabe as "scientific consensus as of 2019." [6] The same editor removed (from FW article) the citation of a 2018 article in Physics World written by Philip Ball (which discusses the 2015 paper at some length) as "The prior edits cite popular science articles that do not reflect academic consensus." [7]
The time crystal article has been in a consensus state, so I think other editors ( @ Sj: ) should take a look at the changes I reverted before the article displays them.
Also, is the IP correct to remove the entire section on Thermodynamics? They disagree with a statement sourced to Science Alert, but other material removed was sourced to Scientific American and academic papers. Thermodynamics seems a worthwhile topic to cover, and blanking the section seems extreme.
Also we should be careful that we rely on secondary sources and RS to evaluate which concepts are of critical importance to the field. Quite a lot has happened since 2015. Perhaps published RS exist that assert the Oshikawa/Watanabe paper from 2015 represents "scientific consensus as of 2019," but until/unless we can cite such RS, the article should not be making such claims. HouseOfChange ( talk) 17:22, 26 March 2019 (UTC)
I have found a citation for the uncited assertion (which I reverted because it was uncited) that two experiments in 2016 were independent work. [1] Similarly, Philip Ball writing in Physics World emphasizes that the two experiments should be treated on an even-handed basis. [2]
IMO, the article should talk about these two experiments with a similar level of detail, and based what independent RS have said about them, not so much on the original primary sources. HouseOfChange ( talk) 16:03, 19 June 2021 (UTC)
References
Monroe, a physicist at the University of Maryland in College Park, and his team used chains of atoms they had constructed for other purposes to make a version of a time crystal...And a group led by researchers at Harvard University in Cambridge, Massachusetts, independently fashioned time crystals out of 'dirty' diamonds. Both versions, which are published this week in Nature, are considered time crystals, but not how Wilczek originally imagined...They are also the first examples of a remarkable type of matter — a collection of quantum particles that constantly changes, and never reaches a steady state.
Last year Monroe and his coworkers reported the characteristic signature of a DTC in an array of 10 ytterbium ions held in a trap, where their spins interact with one another...At the same time, a team at Harvard University led by Mikhail Lukin saw another way to create a quantum system with the requisite disorder: it could come from impurities distributed randomly in a diamond crystal lattice.
Partially quoting a paper from 2012 [8] that described time crystals as "systems with time-periodic ground states that break translational time symmetry" can hardly be our best possible choice. There have now been lots of articles about time crystals, and we should search them for good ways to explain what a time crystal is. Here are some other possibilities.
I think a good clear definition will explain the analogy to crystals and say something informative about the role of symmetry breaking in their realization. What do other editors think? HouseOfChange ( talk) 01:21, 4 August 2021 (UTC)
There is a lot of recent news about time crystals but... Is there some rule of thumb we could use to decide when "this group made a 2021 discovery (link to primary research paper and to the home institution news article)" does or doesn't require a separate paragraph? When independent RS cover somebody's new experiment, we get better context of how it relates to time crystals.
Maybe there should be a separate article about time crystal experiments? Hoping for guidance from more experienced editors. HouseOfChange ( talk) 00:24, 9 August 2021 (UTC)
Wikipedia is an encyclopedia, whose articles are aimed at informing a general audience about notable topics. We rarely cite primary research papers, because topics of general interest should have been treated in an accessible way by secondary or even tertiary sources. If this article should have a section on "Condensed matter in crystalline structures in time", it needs to be a lot clearer why this improves the encyclopedia project, as opposed to why it matters to people who have published scholarly papers to see their work mentioned in Wikipedia.
Time crystalline structures can also be created externally like photonic crystals. The latter do not emerge spontaneously because periodic modulation of the refractive index in space is imposed externally. Resonant periodic driving of a single or many-body systems can reveal condensed matter-like behavior [1] [2]. For example, Anderson and many-body localization in time, topological time crystals, superfluid-Mott insulator phase transition in the time domain can be realized in resonantly driven systems [3] [4] [5], see also [6].
Here is the section I removed. If others feel it belongs in the article, how can it be improved and where should it go? HouseOfChange ( talk) 13:51, 30 August 2021 (UTC)
References
We show that an ultracold atomic cloud bouncing on an oscillating mirror can reveal spontaneous breaking of a discrete time-translation symmetry
Time crystals do not violate the laws of thermodynamics [....] Time crystals do evade the Second Law of Thermodynamics
?
IncompleteBits ( talk) 16:57, 6 November 2021 (UTC)
I reverted an extensive edit talking up the Google experiment, not least because it replaced the accurate description of Google's many collaborators coming from " multiple universities" with the inaccurate claim that all came from "Standford University" [sic]. Could other editors take a look? HouseOfChange ( talk) 20:10, 27 December 2021 (UTC)
Hello, people who know more than I do. I just watched the video at https://m.youtube.com/watch?v=ieDIpgso4no . That was my very first exposure to the term and concept covered by this article, time crystals.
In that video, the speaker says that the 2017 time crystals were not true time crystals. My impression was that they failed to fit the definition in some technical or crucial way. The speaker goes on to say that in 2021, the Google experiment produced true time crystals, and others have as well. I can't say anything about the speaker's source of information or understanding of the material (except of course that they both probably exceed my own, very greatly).
It's also worth noting that the video was posted only about 11 hours ago, so this could be new information, or relatively new, whatever. Yay for bleeding edge science!
So, I've posted this only so that better and more concerned minds can consider whether any of the article needs updating, or not. Should the description of the 2017 results be adjusted? I am not especially invested in the answer, other than the general desire to help Wikipedia be accurate. I won't be checking back, and don't have anything more to contribute to the conversation.
Thanks for all you do, people!
Signed,
Just a casual passer-by, hoping to be helpful. — Preceding unsigned comment added by 24.56.77.201 ( talk) 08:26, 16 June 2022 (UTC)
It would probably be worth including in the article, in light of the fact that our chief interest in time crystals is their apparent (though faux) violation of second law of thermodynamics, by way of perpetual motion. (I say faux because the term 'motion' is questionable in this context, given that the oscillations are trapped in the system and shouldn't be treated as 'free' energy. Actually, if we could quantify the energy that it takes to set up a time crystal, which is then converted into unavailable energy, it would have to be identical to the 'change in entropy', right? But because you're necessarily setting up a system that doesn't have any free energy, it's non-enthalpic, and therefore the net change in entropy is... zero. Augh! It breaks my understanding of thermodynamics. This could use attention from an expert). Atomic putty? Rien! 14:31, 14 September 2022 (UTC)
Currently, the article includes this paragraph:
An earlier "proof" that a time crystal cannot exist in thermal equilibrium [1] was shown to have a subtle error that renders it invalid (See Appendix A of Khemani, Moessner, and Sondhi (2019). [2]). Recent experimental advances in probing discrete time crystals in their periodically driven nonequilibrium states have led to the beginning exploration of novel phases of nonequilibrium matter. [3]
I have disputed this proposed edit, because it references primary research by involved authors rather than secondary source confirming it:
However, the proof was completed shortly after and now is thought to hold [4].
I agree that Wikivoice shouldn't say the proof was wrong if its error has since been corrected. But the primary source cited is dated 2020, plenty of time for secondary source to weigh in on one side of the other. Perhaps the entire paragraph should just be eliminated. What do others think? HouseOfChange ( talk) 23:16, 10 November 2022 (UTC) HouseOfChange ( talk) 23:16, 10 November 2022 (UTC)
References
WO 2015
was invoked but never defined (see the
help page).KMS 2019
was invoked but never defined (see the
help page).else et al 2020
was invoked but never defined (see the
help page).