[HN Gopher] Eternal Change for No Energy: A Time Crystal Finally...
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Eternal Change for No Energy: A Time Crystal Finally Made Real
Author : theafh
Score : 60 points
Date : 2021-07-30 14:14 UTC (8 hours ago)
(HTM) web link (www.quantamagazine.org)
(TXT) w3m dump (www.quantamagazine.org)
| pera wrote:
| What's the difference between this and this other work also from
| the Max Planck Institute published back in February?:
|
| https://is.mpg.de/news/world-s-first-video-recording-of-a-sp...
| high_byte wrote:
| and with that, plain crystals are automatically upgraded to space
| crystals
| rbanffy wrote:
| Space is just time rotated 90 degrees
| high_byte wrote:
| damn those perpendicular-time crystals
| PaulDavisThe1st wrote:
| You're right! But the rotation has to happen in opposite
| directions through the 7th and 9th dimensions.
| morpheos137 wrote:
| can you explain what you mean?
| PaulDavisThe1st wrote:
| Of course not! It's jibberish to the same extent that
| "space is time rotated through 90 degrees" is. Fun, but
| jibberish.
| whatshisface wrote:
| The laws of physics are only symmetric under euclidean
| rotations in the three dimensions of space. When mixing time
| and space, you have to use a hyperbolic rotation, and there
| is no hyperbolic rotation that turns time into space.
| rbanffy wrote:
| And now I am imagining something that's time-amorphous, like a
| time crystal, but that doesn't cycle orderly over a predictable
| set of states at regular intervals, but that does so irregularly
| tracing itself into multiple paths between its possible states.
| thanatos519 wrote:
| That sounds very Stephen Wolfram to me.
| p1mrx wrote:
| Doesn't a glass of water satisfy that definition?
| _game_of_life wrote:
| I stopped listening to anything from quanta magazine after this
| video:
|
| https://youtu.be/HL7DEkXV_60
|
| Where they claim that that a "landmark proof" and one of the
| greatest accomplishments in computer science of 2020 solved THE
| HALTING PROBLEM using "a quantum AI supercomputer."
|
| I looked up the proof and that's not even remotely what the
| authors paper seems to be talking about...
|
| Not to mention you'd both win the Turing award and have it
| renamed after you if you solved the halting problem.
|
| So I guess my question is: Is quanta magazine reputable or just
| more science clickbait? I'm curious what the hacker News audience
| thinks since I am definitely not a quantum physicist.
| teraflop wrote:
| That video segment never mentions "AI", and it never says that
| the halting problem has been solved -- it explicitly says it's
| unsolvable. What it says is that solutions to the halting
| problem could be _verified_ under a certain computational
| model.
|
| That's obviously an extremely rough summary of what the paper
| shows, but I'm not sure how one could do better in a 3-minute
| summary for a non-expert audience. And based on Scott
| Aaronson's response to the paper, it seems like calling it a
| "landmark" result is very reasonable:
|
| > Still, assuming this one stands (as I'm guessing it will), I
| regard it as easily one of the biggest complexity-theoretic
| (and indeed computability-theoretic!) surprises so far in this
| century. Huge congratulations to the authors on what looks to
| be a historic achievement.
|
| https://www.scottaaronson.com/blog/?p=4512
| kevinventullo wrote:
| I've read a few Quanta articles about topics in pure math, and
| they did about as good of a job as one could reasonably expect.
| E.g. they interviewed roughly the same people I would have
| chosen, and the author clearly spent a great deal of time
| trying to make the work accessible without saying anything
| untrue or misleading. Of course, there's a certain amount of
| hype that tends to be a matter of opinion.
|
| Here's an example close to my heart:
| https://www.quantamagazine.org/mathematicians-find-polynomia...
| excalibur wrote:
| > The time crystal is a new category of phases of matter,
| expanding the definition of what a phase is. All other known
| phases, like water or ice, are in thermal equilibrium: Their
| constituent atoms have settled into the state with the lowest
| energy permitted by the ambient temperature, and their properties
| don't change with time. The time crystal is the first "out-of-
| equilibrium" phase: It has order and perfect stability despite
| being in an excited and evolving state.
|
| So to recap, there are now 8 known states of matter: solid,
| liquid, gas, plasma, bose-einstein condensate, time crystal, and
| apparently water and ice.
| swamp40 wrote:
| So it needs a laser, but it doesn't absorb any energy from the
| laser? Hmm.
| FishFoodzD wrote:
| Isn't this just a perpetual motion machine? How can it change,
| while absorbing no energy from a laser, forever? If it's a
| perpetual motion machine, how can that be?
| neatze wrote:
| It is really hard to follow context of article, guess is not
| written for us mortals. My primitive understanding that is most
| likely wrong;
|
| > If it sounds implausible, it is: After much thrill and
| controversy, a 2014 proof showed that Wilczek's prescription
| fails, like all other perpetual-motion machines conceived
| throughout history.
|
| > Furthermore, the spins never absorbed or dissipated net
| energy from the microwave laser, leaving the disorder of the
| system unchanged.
|
| Seems like maintaining stable quantum state A or B costs
| energy, but changing quantum state from A to B or from B to A
| does not somehow introduces additional order/disorder to a
| quantum system and changing state costs energy. (this still
| confuses me, obviously)
| space_fountain wrote:
| I think the difference is a perpetual motion machine ought to
| be able to do useful work. You can hook it up to a shaft and
| generate power ect. This merely moves. I guess this doesn't
| work for some reason (or maybe just doesn't count), but imagine
| a wheel rotating in a perfect vacuum. It can quite happily
| rotate forever without using any additional energy
| FishFoodzD wrote:
| It would still slow down. The blackbody radiation output by
| the wheel would cool it down, and in the same way, all the
| electrons the wheel is made out of will radiate energy as
| they are spun. (Spinning charges are constantly accelerated
| by centripetal force, and accelerated charges radiate.) So
| no, 2nd law of thermodynamics means you can't even keep pace,
| you are always losing energy. So how can these scientists
| claim to have invented perpetual motion?
| neatze wrote:
| This is how I am reading it as an wheel analogy;
|
| 1. Maintaining vacuum state costs energy.
|
| 2. Using energy you can change wheel rotation from clock
| wise to counter clockwise.
|
| 3. By using energy when changing wheel ration, wheel
| rotation energy is not effected.
|
| I am almost sure it is false thought :)
| space_fountain wrote:
| Hum, guess I'm definitely exposing my lack of physics
| knowledge, but my understanding was that entropy is only
| guaranteed to increase or stay the same in any isolated
| system. That the inequality is >= not >. If so while like
| this exact example might not work, there isn't anything
| clearly wrong with something that just has repetitive
| motion
| marcosdumay wrote:
| It's not more of a perpetual motion machine than the molecules
| of a gas moving around, or of a solid vibrating.
| ballenf wrote:
| If the phase changes happen on any kind of non-random
| schedule, however, it would still be introducing information
| into the system. And therefore violating know laws. Right?
| teraflop wrote:
| What known laws would it be violating?
|
| If you're thinking of the second law of thermodynamics,
| bear in mind that popular descriptions that equate
| "entropy" with "information" or "non-randomness" are
| _extremely_ oversimplifying things. A periodic change in a
| system does not necessarily imply a decrease in entropy.
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