Talk:Time crystal

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• https://www.technologyreview.com/s/602541/physicists-create-worlds-first-time-crystal/
• https://arxiv.org/abs/1609.08684

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)Reply

It is relevant, but is really beyond the definition of space-time crystal. I would like to see the study properly published to see if it can get past peer-review. Graeme Bartlett (talk) 09:01, 7 October 2016 (UTC)Reply

This is driving up readership, so I have written something. I don't understand this too well either. Graeme Bartlett (talk) 23:29, 9 October 2016 (UTC)Reply

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)Reply

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)Reply

Where exactly was the 2nd law of thermodynamics broken? I think you have a common misconception of what was actually discovered and what's been done, thanks to pop-sci articles. Take a read here and you'll know why the 2nd law of thermodynamics absolutely wasn't broken:

https://bigthink.com/starts-with-a-bang/time-crystal/

--AloisIrlmaier (talk) 05:56, 14 October 2021 (UTC)Reply

With "you", you must mean Moessner. He is the one who said it. But I fear you will not reach him via a Wikipedia Talk page. --Hob Gadling (talk) 07:15, 14 October 2021 (UTC)Reply

"Evade" doesn't necessarily mean "break", it means you sidestep it. We don't have his full quote but I suspect, as is typical with sensationalist science reporting, that his words have been taken out of context and he meant that you get perpetual motion, typically forbidden by the second law, without actually violating it - hence evading it.

(And 2nd law doesn't state that it always increases, but that it never decreases: it can stand still, for example in a closed many-body localised system it will be stationary). Jaredjeya (talk) 22:54, 4 November 2024 (UTC)Reply

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

Yeah I agree the referencing is kinda obtuse, and will take a while to fix... for now the priority should be on the news and interviews coming out of the Nature publications this month.--Sparkyscience (talk) 11:34, 13 March 2017 (UTC)Reply

But this is definitely on the to-do list! Editors should just add references for the time being however they want and I'll do my best to swoop in and tidy things up, and get round to reformatting at some point --Sparkyscience (talk) 11:41, 13 March 2017 (UTC)Reply

Need someone to write the "Simple English" article ASAP. SammyMajed (talk) 09:00, 10 March 2017 (UTC)Reply

• @SammyMajed: see https://en.wikipedia.org/w/index.php?title=Space-time_crystal&oldid=764370454 -- should we revert back to that version? The current one explains a lot more background, but at too advanced a level to be useful for the average reader here. Graeme Bartlett (talk) 13:09, 10 March 2017 (UTC)Reply

@Graeme Bartlett: Articles should have background, I vote for the "https://en.wikipedia.org/w/index.php?title=Space-time_crystal&oldid=764370454" version to be simplified a notch and put up for the Simple English Wikipedia while keeping the English Wikipedia version as it is SammyMajed (talk) 14:53, 10 March 2017 (UTC)Reply

I think its best to outline areas that need a simplification/further explanation then to revert to a version which is now out of date and misses a lot of key scientific points. If you had to pick a few, what areas are most difficult to understand? Worth noting that I don't think any scientist fully understands the implications of time-crystals, it is frontier of science stuff so is likely to remain a complicated subject however we cut it.--Sparkyscience (talk) 11:39, 13 March 2017 (UTC)Reply

Yea, at the very least, the opening paragraph needs to be in lay-man terms. Body sections of the article can go more into detail. KyuuA4 (Talk:キュウ) 20:24, 15 March 2017 (UTC)Reply

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)Reply

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)Reply

I completely agree. The vast majority of all literature now uses the word "time crystal" to describe the phenomena and the article should be renamed. I think I've seen references to a "phase space crystal" here and there in the literature to describe something similar, but I have not seen "space-time crystal", maybe one of the earlier editors has a RS for the term?--Sparkyscience (talk) 11:29, 13 March 2017 (UTC)Reply

I won't oppose a name change now, as what has happened is that a genuine Space-time crystal cannot be made, and what has been made is related but does not have physical extent in space in the same way so most use now in writings is Time crystal. Not many people are entering our article from the time crystal redirect though, only 493 compared to Space-time crystal with over 53000 page views in the last month. Graeme Bartlett (talk) 12:05, 13 March 2017 (UTC)[1]Reply

I'm pretty sure you can't read anything into the redirects: If I search "time crystal" in Google I will then click on the "space-time crystal" link and this will show up as a "space-time crystal" statistic rather then "time crystal" redirect. You can see comparison of search terms in google here: [2]--Sparkyscience (talk) 13:47, 13 March 2017 (UTC)Reply

That is not a big number. This query https://trends.google.com/trends/explore?date=all&q=time%20crystal,space-time%20crystal,time-crystal,space%20time%20crystal shows more, but may not be what we think. Graeme Bartlett (talk) 01:25, 14 March 2017 (UTC)Reply

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) Reply

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)Reply

It stands for "Many body localization" a big topic at the forefront of condensed matter physics but unfortunately isn't really covered by Wikipedia properly . I can squeeze the term in under the picture caption but unsure how much insight will be gained by the reader as i can't see any obvious article to link to for the term? What are your thoughts?--Sparkyscience (talk) 08:43, 14 March 2017 (UTC)Reply

• @Sparkyscience: I have created a tentative redirect of many-body localization and put an entry for this at MBL. Note that we also have many body problem but that seems too general for this specific case. Andrew D. (talk) 15:09, 15 March 2017 (UTC)Reply

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)Reply

Can the lead-in explain things for 'non-physicists/crystallographers'? 86.146.99.55 (talk) 13:50, 15 March 2017 (UTC)Reply

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)Reply

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.

Indeed. All experimenters and theoreticians make clear that time crystals are not in perpetual motion. – SJ + 07:17, 1 July 2017 (UTC)Reply

This edit request has been answered. Set the |answered= parameter to no to reactivate your request.

The link to "Perpetuum mobile" links to a music reference instead of to the physics perpetual motion page: https://en.wikipedia.org/wiki/Perpetual_motion Samuel Thornkey (talk) 00:41, 16 March 2017 (UTC)Reply

Done DRAGON BOOSTER ★ 04:16, 16 March 2017 (UTC)Reply

chronocrystal (χρόνος + κρύσταλλο[ς]) — Preceding unsigned comment added by 2A02:587:4100:9F00:71BD:A55E:8466:CC77 (talk) 07:22, 16 March 2017 (UTC)Reply

I cannot see this in use for this concept. Its current use is for a game item. Graeme Bartlett (talk) 22:38, 16 March 2017 (UTC)Reply

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)Reply

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)Reply

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)Reply

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)Reply

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:

Lede

• "This allows for the crystal to be in perpetual motion." - untrue, the cited source doesn't say this, indeed no experimenter says this.
• "Time crystals are closely related to the concepts of zero-point energy and the dynamical Casimir effect." - repeated elsewhere in the article. Misleading, partly original synth.

- ZPE isn't related, though you can set up thought experiments where a time crystal is affected by ZPE (as in Chernodub).

- Mendonca writes d. Casimir effect is a 'special case of a time crystal' and 'closely related', but their paper (journal IF: 0.6) only shows that, given a time crystal in an ultra-cold gas, if one varies the density of gas atoms just so, one can create a variation of the d. Casimir effect with phonons. That's not normally what "closely related" means. The fact that one can come up w/ a thought-experiment relating two things does not make them closely related, and time crystals are well defined without either of those other concepts.

• "Time crystals are thought to exhibit topological order" - misleading, a minor speculation, should not be in lede. Possibly a misreading of the source: some think that time crystals, like many other materials, can exhibit topological order, which might allow for more stable crystals [the experiments so far observed crystals that were very unstable]

History

This section looks fine.

• Confusing use of "no-go"; there were no-go arguments & theorems for a variety of assumptions.

Symmetry

• Broken symmetry (2 sections) repeats what's in the detailed article. Only a sentence is needed, not 2 sections.
• Quasienergy: neologism, remove entirely.
• "In either case the apparent non-conservation is in reality a transfer to the vacuum field (i.e. zero-point field)." OR, not remotely in source.
• "The term quasienergy has been coined to explain some of the predicted properties of time crystals." neologism, OR

Topological order

• Not relevant to time crystals (any more than any other matter), should be left out. To the extent that it is accurate, it repeats content from the topological order article, with selective examples.
• The original speculation about Floquet theory gets pretty wild. Not related to the topic, and not supported by sources.
• The original speculation about violating the 2d law of thermodynamics is wild and deceptive. The source says the opposite: that the law is never violated.

Thermodynamics

• The first section is fine, but could be clearer.
• The statement about the no-go theorems is fine to repeat here.
• The section on zero-point energy should be left out. (Is there some sort of ZPE conspiracy that inserts it into any small-scale physics concept? It really isn't related to the definition or exploration of time crystals.)

Related concepts

• Dynamic Casimir effect: better to leave out, for reasons noted above. Not particularly related; needs a better source than Mendonca to suggest it is.

Regards, – SJ + 07:17, 1 July 2017 (UTC)Reply

Changes applied: in particular, the lede was cleaned up, a cleanup notice re-added, and notes were converted to refs (still a bit clunky, since you have to click through from the ref to the biblio entry and then to the original source). Sections on dynamic casimir effect, zero-point energy and topological order left to their dedicated articles. Overall the article is again focused on the topic and reads better, but could still use a pass from someone deeply familier with the field. – SJ + 22:11, 22 July 2017 (UTC)Reply

@SJ: Great cleanup! That was desperately needed; the article had become a "christmas tree" with all kinds of unrelated topics added. --Chetvorno^TALK 21:36, 1 September 2018 (UTC)Reply

I applaud all the good work done by SJ mentioned above. However I still have a problem with one sentence:

"Because a time crystal is a driven (i.e., open) quantum system that is in perpetual motion, it does not violate the laws of thermodynamics."

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)Reply

Changed. Please correct or improve as needed. – SJ + 14:41, 21 September 2017 (UTC)Reply

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)Reply

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)Reply

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)Reply

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)Reply

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.

• IOP 2017, by the same author, "Time crystals are time-periodic self-organized structures postulated by Frank Wilczek in 2012."[9]
• Lodi Valley News 2021, "First, we need to understand what a crystal is for physics: an object with atoms arranged to create a repeating pattern...Now think of a crystal whose pattern does not repeat itself at every specified distance, but at every specified time. That will crystallize time...Motion is not generated by stored energy, but rather by symmetry breaks in the fluid."[10]
• Quanta 2021, "...a time crystal is an object whose parts move in a regular, repeating cycle, sustaining this constant change without burning any energy."[11]
• Science Alert Explainer, post-2019, "Time crystals are similar to regular crystals in that they are based on structures of atoms that repeat. Rather than forming repeating across three dimensions of space, these ones change in a set pattern over time."[12]

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)Reply

I don't think any definition that includes the crystal analogy and symmetry breaking is going to be clear for general readers, although it's going to have to be in the introduction since it is the official definition. I also think the sentence "A discrete time crystal never reaches thermal equilibrium..." is also too confusing for general readers and should be explained in the introduction. The current definition, "....a system or subsystem whose lowest-energy states evolve periodically." is better, but still vague; what does 'evolve' mean?

The def in the third bullet point above is adequately user friendly, but it omits the crucial point that the crystal's quantum nature is the reason it moves perpetually. I would suggest:

"A time crystal is a quantum system of particles whose lowest-energy state is one in which the particles are in repetitive motion."

The system cannot lose energy to the environment and come to rest because it is already in it's quantum ground state. Because of this the motion of the particles does not really represent kinetic energy like other motion, it has "motion without energy".

--Chetvorno^TALK 05:59, 4 August 2021 (UTC)Reply

Thanks, HouseOfChange, for all the great work looking up those possible definitions. The intro looks much improved to me. I didn't know I'd be the only editor expressing an opinion; I'm no expert. Also, just want to make clear, I have nothing against defining the time crystal in the introduction as a system that breaks time symmetry; or stating that it is a "nonequilibrium" system. I just meant there should be clarifying sentences in the intro explaining to nontechnical readers what these statements mean.

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)Reply

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)Reply

Working to understand this piece of the puzzle: Kryzsztov Sacha (pub. 2015) proposed a model of time crystals based on "an ultracold atomic cloud bouncing on an oscillating mirror."^[7] Lingzhen Guo in 2013 proposed another time-crystal analog called "phase space crystals."^[1]

Much of the Wikipedia article, however, reflects secondary sources writing about a different model of time crystals involving periodically driven spin systems. Meanwhile, both Guo and Sacha have written review articles, citing each other's work as examples of "condensed matter physics in time crystals." Unfortunately, there seem to be no independent secondary sources that give a clear explanation of "condensed matter physics in time crystals" -- neither about what it means or about why it is important to understanding time crystals. The article already gives KS credit for an important and early piece of work. Again, I welcome input from other, more experienced editors or people with deeper knowledge of physics. HouseOfChange (talk) 17:56, 31 August 2021 (UTC)Reply

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)Reply

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)Reply

Hi, the reverted edit was done by me I think I deleted that part to write it again as in the first paragraph of the quanta magazine article "Google in collaboration with physicists at Stanford, Princeton and other universities" which seemed better and left it midway with some distraction, the article mentions how the group of Stanford proposed the experiment to Google but it doesn't say anything about the others universities so I had probably Stanford more on my mind and didn't notice but I was aware that it wasn't only Google and Stanford as the edit which included the paragraph about the google experiment with the line "Google and physicists from multiple universities" as currently stands was also done by me so it was really just a mistake.

I was trying to improve what I had edited previously so if there are others problems with the changes I had intended please let me know. Dabed (talk) 21:58, 27 December 2021 (UTC)Reply

@Dabed: Concerning your edit, which cites the rather unbalanced Quanta article four times: My concerns included removing credit from universities other than "Standford" as well as WP:RECENT and WP:WEIGHT. The Google experiment is currently covered in both the Thermodynamics section and the Experiment section. Before adding more highly-technical material about this experiment, I suggest you review the material already in the article about it, as well as the level of detail given for other experiments mentioned in the article. It would be more interesting to hear more about other experiments. HouseOfChange (talk) 03:08, 28 December 2021 (UTC)Reply

@HouseOfChange: I think I explained the best I could the matter about the universities so not sure what more can I say to make it clear so that bad faith isn't assumed. In the paragraph I cited the quanta magazine article once and in this edit I cited it two more times as I added two others experiments mentioned in the article so that is 3 concerning my edits which I agree it wasn't ideal nevertheless all in all I don't understand why it has to be assumed I didn't read the material already present. The google experiment is mentioned once more in the thermodynamics section and in this case the editor probably didn't read the experiment section because he/she duplicated the reference but even then it is not the more cited reference which is reference 38 with 5 citations. I also want to hear about about more experiments and that is why I included the one from google, the one made using magnons and wanted to add two more experiments one using carbon-13 nitrogen-vacancy centres and another using trapped ions qubits. I think these issues are things that could have been edited rather than reverted and I don't agree WP:RECENT and WP:WEIGHT either but this is not the first or last contribution that will amount to nothing for one reason or another and as one can only keep track of a handful of things I will rather move on I try to contribute on other articles. Thank for your work and best regards.Dabed (talk) 06:03, 28 December 2021 (UTC)Reply

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)Reply

A real time crystal would not need the input of any energy. But has minimum energy in its time crystal state. Graeme Bartlett (talk) 08:44, 16 June 2022 (UTC)Reply

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)Reply

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)Reply

We should remove the paragraph. We should also avoid using the term "thermal equilibrium" unless the source itself uses such a broad term, and WO 2015 does not use that term. Rolf H Nelson (talk) 03:17, 13 November 2022 (UTC)Reply

A possible breakthrough? https://www.sciencealert.com/physicists-transformed-a-quantum-computer-into-a-time-crystal Original paper: https://www.nature.com/articles/s41467-024-53077-9

I'll come back when time permits to add this to the article, unless someone else does first. Interesting idea. Hope it works! Pete Tillman (talk) 20:45, 25 November 2024 (UTC)Reply

The core issue is the shift from a continuous model of matter (often assumed in classical physics) to a discrete model (which might be implied in certain quantum or condensed matter systems). The claim that the pre-crystal state is continuous but the crystal state is discrete is based on applying a continuous model of matter in one case and a discrete model of matter in the other. This switch in models to explain a phase transition is not a natural or consistent way to describe the behavior of the system, and it weakens the argument. If we are describing a system with a continuous model, it should remain continuous throughout the phase transition (such as from the pre-crystal state to the crystal state). If we want to use a discrete model, it should also remain discrete before and after the transition. We should not change models to account for symmetry breaking.

The symmetry breaking in time crystals is better framed as time-space rotation symmetry breaking. I argue that time crystals don't break time-translation symmetry, but instead break a symmetry involving rotation in both time and space. The transition to a time crystal should be viewed as a phase transition where the synchronization of periodic motion in time establishes a preferred orientation in space and time.

In a consistent treatment of phase transitions, whether the system is described using a continuous or discrete model, the nature of the symmetry breaking should be handled within the context of the model in use. A phase change shouldn't require a change in the basic modeling framework (from continuous to discrete), because this introduces conceptual inconsistencies. Whether we're talking about a spatial crystal or a time crystal, the transition should be explained without switching between models.

The two-shoed argument—where the pre-crystal state is continuous and the crystal state is discrete—is problematic because it requires changing the model of matter during the explanation. We should consistently describe matter as either continuous or discrete, depending on the context, but not switch between the two to account for symmetry breaking or phase transitions. We can account for the rotational asymmetry of the time crystal in a fully discrete model, or in a fully continuous model. The symmetry breaking that occurs in time crystals should be explained within a single framework (whether continuous or discrete), and explaining the transition between states should not rely upon a model change.

TheodoricStier (talk) 21:25, 8 February 2025 (UTC)Reply

Time crystal as having oscillations in the lowest energy state seems in agreement with that in relativistic QM psi~exp(-i E t/hbar) requires E = mc2, so literally mass itself propels oscillations - confirmed experimentally e.g. for electron Zitterbewegung/de Broglie clock ( https://link.springer.com/article/10.1007/s10701-008-9225-1 ), or neutrino oscillations with 3 mass eigenstates.

So are electrons and neutrinos time crystals? Do time crystal "no-go" theorems prevent such oscillations? (my approach avoiding them) Jarek Duda (talk) 11:48, 24 February 2025 (UTC)Reply

A genuine time crystal would also be periodic in 3 dimensions as well as in time. On particle is not a crystal, and the the claims so far of making a "time crystal" have failed to be a real crystal, just some oscillating system. Graeme Bartlett (talk) 23:48, 13 March 2025 (UTC)Reply

Definition in this Wikipedia article is "a time crystal is a quantum system of particles whose lowest-energy state is one in which the particles are in repetitive motion." - for example pendulum does not satisfy it as energy minimization would stop it, but relativistic QM and experiments show that at least electron and neutrinos have some repetitive evolution already in the lowest energy state. In non-perturbative picture, they are some field configurations, for which energy minimization already leads to periodic process (against time crystal "no-to theorems"). Jarek Duda (talk) 05:23, 20 March 2025 (UTC)Reply

I've been using Google's Gemini 2.5 Pro Experimental large language model to create summaries for the most popular articles with {{Technical}} templates. This article, Time crystal, has such a template above the entire article. Here is the paragraph summary at grade 5 reading level which Gemini 2.5 Pro suggested:

A time crystal is a special kind of stuff where its tiny parts, called particles, move in a pattern that repeats over and over again in time, like a clock ticking forever. Normal crystals, like salt or snowflakes, have patterns in space that don't move. But time crystals keep moving in their special rhythm even when they have the lowest possible energy and should be still. Scientists first thought about time crystals, and then later, other scientists were able to actually make them in labs. They aren't magic machines that make free energy, but they are a new discovery that might be useful for things like building powerful computers in the future.

While I have read and may have made some modifications to that summary, I am not going to add it to the article because I want other editors to review, revise if appropriate, and add it instead. This is an experiment with a few dozen articles initially to see how these suggestions are received, and after a week or two, I will decide how to proceed. Thank you for your consideration. Cramulator (talk) 12:49, 2 April 2025 (UTC)Reply

Use of LLM needs to be discussed by the entire Wikipedia community, not just those interested in one article. You can start at WP:Village pump. Sundayclose (talk) 16:14, 2 April 2025 (UTC)Reply

I appreciate your innovative effort! But, I don't think readers who want to learn more about technical subjects are looking for Grade 5 level text like "special kind of stuff" or "tiny parts, called particles." HouseOfChange (talk) 17:42, 2 April 2025 (UTC)Reply

I am retracting this and the other LLM-generated suggestions due to clear negative consensus at the Village Pump. I will be posting a thorough postmortem report in mid-April to the source code release page. Thanks to all who commented on the suggestions both negatively and positively, and especially to those editors who have manually addressed the overly technical cleanup issue on six, so far, of the 68 articles where suggestions were posted. Cramulator (talk) 00:15, 5 April 2025 (UTC)Reply

The Science Channel reported on June 22, 2011 that Hao-Tan Li had proposed to Hartmut Häffner UC Berkley that an ion ring time crystal (which the show referred to as a "Time Ring") could demonstrate spontaneous rotation due to quantum time fluctuations. Since this reference predates other citations in the article, I'm adding it to the history section. Sparkie82 (t•c) 23:41, 19 October 2025 (UTC)Reply

You need a better RS than a link to a YouTube video, including RS that "ion ring" is equivalent to time crystal. Not a single other result from Google for "Hao-Tan Li" + "time crystal." HouseOfChange (talk) 17:45, 20 October 2025 (UTC)Reply

The source that was referenced for the claim is the TV documentary series itself, not the YouTube video. The link to the yt video was included merely to facilitate verification. Since the YouTube channel that posted the copy of the episode is the publisher itself, Science Channel (it has a YouTube verification check mark), I presume that the video has not been tampered with, however, that's always a possibility and if someone has access to another, contemporaneous copy of the episode which could be verified, that would be useful. Until then I think we assume that the yt copy is authentic.

I wouldn't propose using a TV documentary as a source for a scientific or technical claim. The claim here is not a scientific claim, it's a claim about what someone is reported to have said. The producers claim that Li proposed to Häffner at Berkeley sometime before June 22, 2011 (air date of the episode) that an ion ring cooled to its ground state near 0°K would be set in motion by quantum fluctuations in time. The journalists who produced the documentary appear to have had direct access to Häffner and I know of no challenges to the reliability of the producers generally, so I think we can use them as a reliable source for this nonscientific claim.

As to whether what Li proposed was a "time crystal", it appears to fall within the scope of the definition that is currently outlined in the lead of this WP article, "a time crystal is a quantum system of particles whose lowest-energy state is one in which the particles are in repetitive motion." An ion ring itself is not necessarily a time crystal, but an ion ring cooled to its ground state and rotating certainly is. Because this is a very new area of research, the definitions of specific terminology are in flux and in the future the definition of a "time crystal" may settle on a more restrictive meaning, perhaps restricted only to periodically driven systems in the domain of quantum computing. In any case, wherever the definition finally settles, the time crystal that Li proposed was an important event in the historical development of the topic.

As to the paucity of public citation for Li, I think that may be due to the fact that he is an experimental physicist, not a theoretical physicist and that's sometimes harder for the academy to digest. Li has been published in later experimental work on time crystals in quantum computing (google scholar search).

As it turned out, what Li proposed (spontaneous rotation) may not be possible due to the later theoretical work of Watanabe–Oshikawa who claim that it is not possible in equilibrium and later work that creates them with initial periodic input. However, I think Wilczek's proposal was also restricted by Watanabe–Oshikawa, but I'm not sure because I haven't read his paper.

In any case, the documentary is certainly a contemporaneous, reliable source for this nonscientific claim about what someone said and can be used as a citation to support the claim, especially given that its publication predated Wilczek's paper. We can include a statement in the WP article that Li's proposal was not initially published by a peer-reviewed source and that it was contemporaneously reported by Science Channel, if that makes you more comfortable. Sparkie82 (t•c) 16:15, 21 October 2025 (UTC)Reply

One mention in a popular science program of somebody's hearsay claim is not RS evidence for what you want the article to claim. There would specifically need to be RS to connect Li's concept to time crystals, because otherwise it is WP:SYNTH to assert (without supporting RS) that ion rings are time crystals. HouseOfChange (talk) 21:29, 21 October 2025 (UTC)Reply

I think anyone familiar with the topic will recognize that Li's proposal fits the definition of a time crystal without needing any analysis. That's the less controversial part of this. The question is when did he make the proposal? Further investigation has turned up discrepancies that may indicate that the copy of the episode posted to YouTube may have been tapered with, possibly by the publisher themselves (Science Channel), so that it includes an interview with Häffner which actually took place a couple years after the episode had aired. I'll continue to investigate this, but for now I agree that we should hold off adding the content to the article until this is cleared up.

Also, due a transcription error, I believe that the correct spelling of Li's name is actually Tongcang Li.Sparkie82 (t•c) 16:10, 23 October 2025 (UTC)Reply

I researched this some more and this is what I think happened. The Science Channel originally aired Season 2, Episode 3 on June 22, 2011 titled "Does Time Really Exist?" which didn't include the Häffner/Tongcang research. Then a couple of years later they aired Season 5, Episode 10 on June 23, 2014 titled "When Did Time Begin?" which featured an interview with Häffner and described the Häffner/Tongcang time crystal research. Then a few days ago a video was posted on The Science Channel's YouTube channel with the title "SEASON 2, EP. 3 - DOES TIME REALLY EXIST", however, the video was tampered with and portions of the scenes of the Häffner/Tongcang research from Season 5, Episode 10 were inserted into the older episode.

I don't know who inserted those scenes into the copy that was posted on YouTube, but it also contain several other scenes from other episodes and some of the content from the originally aired S02E03 episode were missing from that copy. So, although The Science Channel generally has done a good job at presenting factual information in their documentaries, apparently they are not a reliable source to obtain clean copies of their past episodes.

So the bottom line is that the Häffner/Tongcang time crystal research didn't predate Frank Wilczek's paper, even though The Discover Channel's Through the Wormhole S02E03 episode posted on YouTube indicates that it did. Sparkie82 (t•c) 11:08, 24 October 2025 (UTC)Reply