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Physicists Create World’s First Time Crystal
- nchallak 10y agoEver since I saw my parents' initial skepticism to the use of handheld devices (smartphones, tablets etc.) I have always wondered what such a mental block for my generation might be like. It could very well be an invention such as this that is considered speculative today which might become viable overnight. My kid may someday wonder why his dad doesn't understand basic quantum phenomena.
- code51 10y agoCan someone explain what computations using __zero energy__ from related article [1] actually means ? [1] https://www.technologyreview.com/s/426917/physicists-predict-the-existence-of-time-crystals/ https://www.technologyreview.com/s/426917/physicists-predict... """ Another is the possibility that it may be possible to exploit time crystals to perform computations using zero energy. As Wilczek puts it, “it is interesting to speculate that a…quantum mechanical system whose states could be interpreted as a collection of qubits, could be engineered to traverse a programmed landscape of structured states in Hilbert space over time.” """
- helloworldimsad 10y agohttps://en.wikipedia.org/wiki/Zero-point_energy https://en.wikipedia.org/wiki/Zero-point_energy
- Strilanc 10y agoThey literally mean "not spending any energy doing the computation". We spend energy on computation for two fundamental reasons: 1) zeroing data and 2) error correction. You avoid zeroing data by doing reversible computation. You avoid error correction by finding really really well behaved / stable systems. Time crystals are reversible basically by definition, and Wilczek is saying that maybe there might be some time crystals that are also well behaved and do something interesting enough to encode computations.
- dangirsh 10y agoIIRC reversible computations only take zero energy if you perform them infinitely slowly.
- lgas 10y agoJust curious, is there a difference between infinitely slowly and not at all?
- drdeca 10y agoI think the idea is that as the speed approaches 0, the energy cost also approaches 0.
- cyphar 10y ago"Infinitely slowly" is a theme in physics. What is actually meant by the term is "slow enough that you can approximate it as being infinitely slow". Now, obviously the idea of approximating an infinite value with a finite one seems dodgy, but the idea is that if some process converges to the "purely theoretical and infinitely slow" solution quickly then you can make that kind of approximation (physics is generally not obsessed with precision). As a concrete example, most of thermodynamics becomes insanely complicated for very rapid changes in pressure and temperature. And in many cases, you cannot actually compute the state of the system (without making a bunch of approximations). But, if you make some assumptions and approximations, thermodynamics becomes much more simple even though you've added some error factors due to your approximations (but it's definitely "good enough"). In general, the first thing you learn as part of a physics degree is that approximations and assumptions are just part of how you do science. Without them, we'd all be stuck dealing with insanely complicated equations that probably are not solvable. And at the end of the day, the unsolvable part of whatever equation you're dealing with wouldn't actually have a significant effect on the result (so you can generally ignore it).
- mickronome 10y agoI'm thinking that if the computation is actually the time evolution of a suitably structured time crystal, one which by definition is traversing/existing in its own ground state. Then either no computation can be done, or it must not require any energy. Reading out the answer must AFAIU (which is very superficial) however take energy, not unlikely to be exactly proportional to any part of the answer not read / erased, and thus closing the apparent loophole, and making you still being right :)
- roywiggins 10y agoI think they might be talking about reversible computing? https://en.wikipedia.org/wiki/Reversible_computing?wprov=sfla1 https://en.wikipedia.org/wiki/Reversible_computing?wprov=sfl...
- happyslobro 10y agoUgh, that title though... WTH is a time crystal, and who decided to call it that? I'm not clicking the bait to find out.
- schoen 10y agoApparently, it is serious physics and a totally new category of engineered physical system. So not clickbait.
- happyslobro 10y agoThanks for the heads up, sorry about the knee-jerk reaction.
- lscharen 10y agoThe core idea is not too strange, actually. A "normal" crystal has a repeating structure in space; a time crystal is a construct with a repeating temporal structure.
- ww520 10y agoI'm curious what does the temporal structure look like? Edit: have just looked it up. Looks like it's basically 3-D structure with repeated motion over time.
- radarsat1 10y agoDoes that mean it is continuously changing in a repetitive fashion?
- krapp 10y agoapparently yes, but because it's in a low energy state, it's impossible to extract any energy from it and do work (otherwise it would be a perpetual motion machine.)
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- hprotagonist 10y agoAnd somewhere, high in the ramtops, Lu-Tze has just developed a crick in his neck and he almost knows why.
- panglott 10y agoWhat are time crystals? Try this: Physicists Predict The Existence of Time Crystals https://www.technologyreview.com/s/426917/physicists-predict-the-existence-of-time-crystals/ https://www.technologyreview.com/s/426917/physicists-predict...
- brathouz 10y agoThis is also helpful: How to Build A Space-Time Crystal https://www.technologyreview.com/s/428334/how-to-build-a-space-time-crystal/ https://www.technologyreview.com/s/428334/how-to-build-a-spa...
- _puk 10y agoThanks for both those links. That article is from 2012 and quotes: "If that’s the case, we ought to be reading the details about the first space-time crystal sometime in the days and weeks to come. " Was there something non obvious they had to overcome that took the extra few years to produce these space-time crystals? (I use the term non obvious as if this was not all way beyond my ken!)
- brathouz 10y agoThe 2012 article said they were using beryllium ions, Wikipedia says in 2013 they were planning on using calcium ions, and now the 2016 article says they used ytterbium ions. Without more content to go on, we can only guess about these changes. In any event, they sure seem to have made a lot of progress in just a few years. I look forward to reading more about this, as well as listening to Neil deGrasse Tyson describe it in his infectiously enthusiastic way.
- devnill 10y agoThis is a fascinating concept. What kinds of applications could time crystals be used for? Time locked crypto that doesn't rely on proof of work jumps to mind, but I'm by no means an expert on either cryptography or quantum mechanics.
- jdc0589 10y agoI'm definitely too dumb for this.
- nwrk 10y agoJoining you. Saw some potential concept here [1] [1] Back to the future (1985) http://www.imdb.com/title/tt0088763/ http://www.imdb.com/title/tt0088763/
- skykooler 10y agoCould this be used for very stable time measurements, as an alternative to atomic clocks?
- _puk 10y agoFrom @brathouz link above.. "One reason why space-time crystals are interesting is that their periodicity in time makes them natural clocks. So there should be plenty of people with more than a passing interesting in making one." So I took from that, yes, this could be an alternative to atomic clocks.
- dysfunctor 10y agoI don't know anything about anything, but I want to enumerate some things I learned reading this article, and if someone actually knows what they're talking about and sees fit to take pity on me, please correct me so that I can understand what this actually means. So a time crystal appears to be made up of real matter. The article mentions ions that are arranged in a certain particular way, cooled in order to reduce their energy, and this still makes sense so far. So, the idea is to create a closed loop of sorts from a temporal perspective. I'm imagining an object as a set of states that the object can be observed in, and if there was a loop, it'd be possible to observe a certain sequence of states over and over. The arrangement of the ions is important, and one of the properties is the spin, which is possible to change with a laser beam, because obviously. Anyways, I guess the frequency of the oscillation of the ions changing spin, since they interact with each other in a domino fashion, can be controlled with the frequency of the laser. They did this, and observed the ions changing in such a way where there was no driving influence and it's implied that the reason that this behavior was observed is because time symmetry was broken, which is just a fancy way of alleging that the universe is non-deterministic, I think. Maybe this will eventually be useful?
- timelincoln 10y agoI definitely don't think the conclusion is that the universe is non-deterministic, the idea is that when energy is lost symmetry is broken, and motion through time seems to be analogous to shape in space, in terms of this symmetry breaking effect.
- dysfunctor 10y agoCan you explain what you mean when you say motion through time, and shape in space? I was under the impression that the whole idea of time symmetry revolved around being able to "zip/fold/traverse/map" both forwards and backwards in time. It's my understanding that such a concept would imply determinism, because time is really just a set of states, in the smallest possible interval of time. I also don't understand why the time crystal loses energy over time if it is trapped in a temporal loop. I mean obviously there's not such a thing as perpetual energy, but I would think that the energy of a certain object at a particular frame in the set of states that is time, then when it returns to that state from either direction, it should be the same. Edit: This is meant to be inquisitive, not necessarily interrogative. Thanks!
- M_Grey 10y agoThis is very interesting, but I'm frankly not convinced that they've actually created a spacetime crystal. Either way though, it's a fascinating bit of work.
- m3kw9 10y agoWhat are they used for? A required part for a time machine??
- obi1kenobi 10y agoDupe: https://news.ycombinator.com/item?id=12646342 https://news.ycombinator.com/item?id=12646342
- sctbpwn 10y agoyours sucks tho
- ge96 10y agoSuper jail Time police
- davesque 10y agoI figured this article would fly over my head (which it mostly did), but it was actually a very fun read. My main takeaway was the paradox that the interesting arrangement of matter could be in its lowest energy state, yet still moving. And that no energy could be extracted from this movement. I'm probably butchering the concept with my misuse of terminology but whatevs.
- deleted 10y ago[deleted]
- lisper 10y agoYou're not that far off. The particles aren't really moving, i.e. they are not going from one spatial location to another. What is happening is that they are changing quantum spin states, and the spin states are changing in such a way that it appears that a circular arrangement of atoms is rotating. This is a reflection of the fact that an atom isn't really a thing (there are no "things", i.e. there are no particles) it's just a quantum state, so if you have a quantum system A in state 1 and system B in state 2, and system A transitions to state 2 and system B transitions to state 1 then this end result is indistinguishable from the two systems having swapped locations. We call this "moving" because classical motion is the only mechanism we're familiar with in everyday life that allows two systems to swap locations. But that kind of moving is not what is happening here.
- Jcol1 10y agoIsn't the entire universe one quantum system? If so, how can we talk about discrete systems. Also, when you say there are not discrete things, do you mean in the QFT sense of field excitations?
- lisper 10y ago> Isn't the entire universe one quantum system? Yes. > If so, how can we talk about discrete systems. That is an excellent question! And the answer is that when you do the math, the result of taking a subset of the wave function (the mathematical operation is called a "trace") is something that looks like a classical system. If you want the details, see this paper: http://www.flownet.com/ron/QM.pdf http://www.flownet.com/ron/QM.pdf Or this video https://www.youtube.com/watch?v=dEaecUuEqfc https://www.youtube.com/watch?v=dEaecUuEqfc which covers the same material.
- pera 10y agowow that was fast! https://news.ycombinator.com/item?id=12474029 https://news.ycombinator.com/item?id=12474029 ("Time crystals might exist after all")
- slackstation 10y agoI hope you like time paradoxes because this is how you get trapped in a time paradox.
- formula1 10y agoCorrect me if If Im wrong. A time crystal is a cycle at atomic level. - matter / energy is neither added nor removed to retain shape/movement - the energy/matter within the "crystal" change state/position in a repeating and/or predictable matter - pattern retains even when the energy is at extreme lows This would be analogous to a water cycle. The water changes state in a predictable manner, water heats up (due to the sun) and evaporates. As the molecules get closer to space, the cool and attract each other to form clouds. The clouds hit a maximum and rain occurs flowing back into bodies of water again. The difference is that the water cycle needs the presence of heat/cooling from external sources while the time crystal can exist at "zero degree" temperatures.
- yarou 10y agoCould this really be used for self-correcting quantum memory, as the article suggests?
- klunger 10y ago>But the laws of physics are not only symmetrical in space but also in time. Can someone explain what this means? It makes sense that physical laws are symmetrical in space. But in time? I thought that would not be the case because of entropy/irreversible processes etc. What am I missing? The whole article rests on this premise.
- jbmorgado 10y agoThermodynamics (from where you get entropy) are a statistical description of physical laws taking process over many particles. When you look at each particle in the thermodynamic system, you can easily see there is indeed simmetry in time.
- proxy176590 10y agoNoethers' theorem: https://en.m.wikipedia.org/wiki/Noether%27s_theorem https://en.m.wikipedia.org/wiki/Noether%27s_theorem Groundbreaking stuff. But it is not something you would want to go over in a weekend.
- cyphar 10y ago"The arrow of time" which you're referring to (entropy increasing in closed systems) is something that is IMO still puzzling in the field of physics. To be clear, entropy isn't a "force" its just a statistical effect (a very large number of particles in a system are always going to be more likely to be in a macrostate that has the most microstates -- meaning that the system will tend towards more "disordered" states). However, it should be noted that the arrow of time only applies to the macroscopic universe. All of the laws of physics (in this article's case it's quantum mechanics) are time symmetric (if you play the experiment in reverse you couldn't tell it was being done in reverse -- which is what you can see in Feynman diagrams). So at the heart of it, the universe is very symmetric in time. To quote Primer: "What's the one variable in all of the equations of heat and matter? What's the one variable that you can turn negative and still get rational answers? Its not energy, it's not mass..." [It's time].
- JonnieCache 10y agoHere's a link to the videos from FXQi's Setting Time Aright conference, where there are lots of talks addressing the relationships between cosmology, QM and entropy with regards to time, with David Albert, Sean Carroll, Max Tegmark, Tim Maudlin, etc etc. https://www.youtube.com/watch?v=QR9reQrumS0&list=PL1FA30AE298BA990D&index=27 https://www.youtube.com/watch?v=QR9reQrumS0&list=PL1FA30AE29... Spolier alert: they don't really know whats going on, and they disagree pretty strongly. Decoherence seems related to the thermodynamic arrow of time: you can't un-measure something, but famously we don't know how to interpret that, many worlds blah blah.
- op00to 10y agoEARTH HAS 4 CORNER SIMULTANEOUS 4-DAY TIME CUBE WITHIN SINGLE ROTATION. 4 CORNER DAYS PROVES 1 DAY 1 GOD IS TAUGHT EVIL. IGNORANCE OF TIMECUBE4 SIMPLE MATH IS RETARDATION AND EVIL EDUCATION DAMNATION. CUBELESS AMERICANS DESERVE - AND SHALL BE EXTERMINATED.
- drdeca 10y agoI don't remember the timecube website saying that people should be exterminated? It called the author the wisest human and such, but I don't think it called for extermination? Did it?
- dmd 10y agoYup. https://web.archive.org/web/20150309102116/http://www.timecube.com/ https://web.archive.org/web/20150309102116/http://www.timecu...
- blippityBlop 10y agoSo, states change without physical objects changing position. Meanwhile we pitiful humans, have a hard time distinguishing the objects that exchange states. ...and can someone tell me where the actual time comes into play? Sure, one can say it is "something not unlike" the manipulation of time, and yet... somehow... it seems like we're just deciding to call it something it is not, since it certainly seems similar enough. If I carve a piece of wood, such that it resembles a gun, it can play the part of a gun, but only until a person with an actual gun challenges me to a duel.
- gravypod 10y agoCould this be used like a piezoelectric in a clock except powered by time rather then a charge applied to a quartz crystal?
- dschiptsov 10y agoOh. From which substance?
- dschiptsov 10y agoNot that much has been changed since the times of Egyptian pyramids - producing himeras and pure abstractions out of words and socially conditioned mental constructs is still one of the most rewarding occupation.
- edem 10y agoCan you explain in layman's terms what a time crystal is? I'm not sure I understood it right. Is this like a RAM which has persistent state?