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Researchers Identify 'Tipping Point' Between Quantum and Classical Worlds

Posted by Soulskill on from the border-between-hostile-nations dept.

wjcofkc sends this report from R&D Magazine: If we are ever to fully harness the power of light for use in optical devices, it is necessary to understand photons — the fundamental unit of light. Achieving such understanding, however, is easier said than done. That's because the physical behavior of photons — similar to electrons and other sub-atomic particles — is characterized not by classical physics, but by quantum mechanics.

Now, in a study published in Physical Review Letters (abstract), scientists from Bar-Ilan University have observed the point at which classical and quantum behavior converge. Using a fiber-based nonlinear process, the researchers were able to observe how, and under what conditions, 'classical' physical behavior emerges from the quantum world.

18 of 83 comments (clear)

  1. Quantum first post by Kjella · · Score: 4, Funny

    You won't know if it's first until it's observed.... and it's not :(

    --
    Live today, because you never know what tomorrow brings
  2. Heisenberg compensator ... by gstoddart · · Score: 3, Interesting

    Will someone please tell me this gives us a basis for Heisenberg compensator?

    Because that would be awesome.

    I'm also hoping this whole thing "that, when unobserved, the photons exist in all possible states simultaneously" eventually goes away.

    It has to be that we can't know what state it's in, not that it's actually in all of them. Can't it? Please? At some point, this quantum stuff should stop being magic.

    --
    Lost at C:>. Found at C.
    1. Re:Heisenberg compensator ... by Greyfox · · Score: 4, Insightful

      Every time they test it, it turns out it actually IS magic, though.

      --

      I'm trying to teach myself to set people on fire with my mind... Is it hot in here?

    2. Re:Heisenberg compensator ... by ledow · · Score: 4, Informative

      As far as I understand it:

      The problem is that it is not in any one state, until observed. Then we just see a snapshot of our particular history that led to that observation. Observation determines the state but also modifies the system forever more, too.

      One hypothesis of this leads to the "many worlds" interpretation" - it's in only in one state but until we actually look (and therefore modify the system) we don't (can't) know which particular universe of possibilities we happen(ed) to be in.

      Unfortunately, quantum physics gets a lot weirder, which only serves to show us how little we know of it. I get lost in it as it's maths way beyond my capability nowadays (despite a maths degree), but as far as my friends in the research fields explain stuff, you can even get things such as particles "borrowing" energy from their future selves (at least, that's one hypothesis of what they are doing) - they don't have to energy to do X, suddenly they acquire it, then they always have pay it back afterwards. It only works if you consider time as "just another dimension" or if you include other spatial dimensions they could be getting this energy from.

      Though we might be able to describe a convergence between classical and quantum mathematically (at some point in the future), the outcome is always going to be the same because we're just 4-dimensional creatures. Weird stuff is going to happen.

      Physics is going to get a lot harder for us long before it gets any easier. Breakthroughs are few and far between and we're only now properly confirming stuff that was discovered / hypothesised in the 20's, 30's, 40's, etc. (don't forget, technically quantum mechanics goes back as far as the late 1800's!).

    3. Re:Heisenberg compensator ... by boristdog · · Score: 4, Funny

      Quantum physics used to confuse me too, but then I started smoking really good weed. Now, it is starting to make sense.
      Seriously. Drugs can help you understand this stuff. I may need DMT to fully comprehend quantum physics, though.

    4. Re:Heisenberg compensator ... by squiggleslash · · Score: 4, Interesting

      You think you have problems? I'm still trying to get my head around "It's both a particle... AND a wave!". How the f--- does that work? It doesn't even make any sense! It's insane! Wave things are not particles, and particle things are not waves!

      (Note: yes, I know, it's true, I've seen the double slit experiment et al, I'm not doubting the science, I'm just saying my brain is too small to understand it. So put me in a position where I have to understand that something is in every state possible until observed, and... well, the worst part is I can visualize it, but only in a way I know deep down is wrong...)

      --
      You are not alone. This is not normal. None of this is normal.
    5. Re:Heisenberg compensator ... by Anna+Merikin · · Score: 4, Insightful

      You may be experiencing the difference between being very smart and being brilliant. I have run across this many times. When brilliant people agree and I don't understand the basics, I have to admit defeat, as if I were playing chess against a Grand Master.

    6. Re:Heisenberg compensator ... by oodaloop · · Score: 4, Insightful

      The universe is under no obligation to make sense to a bunch of shaved apes.

      --
      Tic-Tac-Toe, Global Thermonuclear War, and relationships all have the same winning move.
    7. Re:Heisenberg compensator ... by ledow · · Score: 5, Interesting

      This is just supposition, but it's the way I choose to understand it. Note: This is probably not science.

      Imagine you're a time traveller but in the classic Hollywood sense where timelines can be broken without the end of the universe, etc. Marty McFly doesn't have to worry about standing next to his former self and breathing in the oxygen he would have originally breathed in, etc.

      You can go back in time, steal some cash from yourself, bring it back to a different timeline, use it to make yourself rich. It's all fine. So long as, at some point, you can back and put that money back for you to steal in the first place. This is similar to how particles they borrow energy. So long as nobody notices (in this case, so long as the energy is returned before the "uncertainty" in the uncertainty principle can be resolved), you're golden.

      Additionally, you are both "in" the room stealing the cash and "out" of the room simultaneously at the same time because you've been jumping back and forth in time (and maybe even in the room watching yourself stealing the cash in order to put it back once you're gone). In one timeline, in 1956, you were there. In another, at the EXACT SAME TIME, you weren't. So asking "where were you at this exact time in 1956?" doesn't give a simple answer. I was here. I was there. I was not here at all. And I was all of them at the same "time".

      Time is just a dimension, so it's one hypothesis that particles may well be doing exactly this - hopping back and forth through other dimensions of space (and thus disappearing from ours and reappearing somewhere else), jumping back and forth in time.

      So long as they repay their debts, it all works out and doesn't violate (certain readings of) energy conservation laws. And particles aren't intelligent creatures that decide to do this, they may just be "things" bouncing through dimensions quite ordinary to themselves but "time", "parallel universes", "alternative histories" etc. to us. Following even the simplest of physical rules in those circumstances could look like the weirdest actions ever from certain points of view.

      Imagine you're on a 2D universe, you are a piece of paper and cannot perceive things not on your surface. A "ghost-like" car tyre passing through your universe will come from nowhere, grow, change shape, look odd, etc. and then disappear and never have looked like a car tyre. Same kind of thing. If you can't perceive the extra dimensions, this horrible weird-shaped thing just pops into existence, wobbles about a bit as a strange-shaped silhouette, maybe forms a hole in the middle if it fell the right way, then disappears. Or maybe it fell perfectly straight and you ONLY ever perceived a rectangle-like shape coming and going. Same object, same thing happening, tiny change in parameters, totally different outcomes that are very unpredictable for you.

      The problem with quantum stuff is that we just don't perceive other dimensions at all, but the maths does.

      (x) describes how far along a ruler you are.
      (x,y) describes where a pixel is on a 2D screen
      (x,y,z) describes where you are in a 3D world.
      (x,y,z,t) describes an EXACT point in space and the time you were there (e.g. your birth).
      (x,y,z,t,q)? We have no way for you to perceive that. But mathematically it's just another co-ordinate.

      Don't expect a layman to understand it. The geniuses don't understand it. They can describe it. They can measure it. They can produce the formulae. But, just taking the knock-on effects and working backwards, they'd have nothing. It's only because the maths comes up with weird outcomes and that we then FIND those weird outcomes in the universe that anything actually looks right. Trying to play it backwards from the weird outcomes to those formulae that you can't understand is never going to help you.

      It's like being a blind man and wondering how people can know there's a silent car coming when you can only detect a car's sound. If you can't perceive entire dimensions that - we're pretty sure - are required to exist for quantum mathematics to work, then you're only ever going to see a third of the story (our current best guess is 11 dimensions - we think - as a minimum? So eleven letters in the above example!).

    8. Re:Heisenberg compensator ... by byornski · · Score: 3, Informative
      I think you should have a look at Bell's theorem.

      'No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics.'

      In this case, local hidden variables refer to what you describe as it being in a single state and us just not knowing. Without faster-than-light information transfer (which we cannot have if causality is to hold within relativity), it is not possible that 'the system is in a state and we just don't know it. '. Quoting wikipedia,

      In a theory in which parameters are added to quantum mechanics to determine the results of individual measurements, without changing the statistical predictions, there must be a mechanism whereby the setting of one measuring device can influence the reading of another instrument, however remote. Moreover, the signal involved must propagate instantaneously, so that a theory could not be Lorentz invariant.

      This has been shown experimentally using Bell's equations and this work got him nominated for a Nobel prize but died before it was awarded that year.

    9. Re:Heisenberg compensator ... by l0n3s0m3phr34k · · Score: 3, Funny

      I can visualize exactly what these interactions would look like. Borrowing energy from it's future self isn't really THAT weird, it's still maintaining the same total amount over it's lifetime. It's both a particle and a wave because, at that size and energy level, it exists outside of our macro existence. And DMT isn't really strong enough for this nor does it last very long; to really grok it you need dextromethorphan hydrobromide in large quantities. It's a milligram per kilo formula, "large quantities" as compared to the standard 15mg dose; to reach the place you need between 1.5-2 grams. The set-up is also very important, I suggest finding some TED talks, documentaries, college course broadcasts, etc, that go into these ideas you can't quite grasp...about 8 hours of them. Comfy chair, dark room, dose yourself and let it roll. You will visit places internally that you didn't know existed, see things that will break down those macro walls. You might even meet entities that will explain it to you. I'm assuming these entities are whatever is playing mixed in with your own thoughts; but you'll be so dissociated you can have in-depth conversations with them and "learn" things in a radical new way.

      Having a 169 IQ helps too, but anyone can reach quantum visualization and comprehension this way. You still won't be able to explain it to most; it just doesn't sync with our macro experience. But you will grok it.

    10. Re:Heisenberg compensator ... by ClickOnThis · · Score: 4, Insightful

      It just sounds barking mad to a layman.

      Not just to a layman. To quote Richard Feynman: "I think I can safely say that nobody understands quantum mechanics."

      And there are plenty more quotes in that spirit.

      --
      If it weren't for deadlines, nothing would be late.
    11. Re:Heisenberg compensator ... by cmdahler · · Score: 5, Insightful

      Consider this scenario. You are a two dimensional creature. You are only able to experience your reality as a flat plane. Up and down have no meaning to you; these are concepts quite beyond your comprehension. You cannot imagine a 3 dimensional object any more than we, in our 3 dimensional world, can imagine what a 4 dimensional object would look like.

      Now, in your 2 dimensional world, creature, I, as a 3 dimensional God-like character, am going to take a circle, anything round, and shove it down through your plane of existence. What would you experience? You would experience at the very first, a single point suddenly appearing as if out of nowhere. This single point splits into two points that diverge from each other at a steady rate. Yet if I stopped pushing the ring through your plane for a moment and let you examine one of those two points that you can see, you would find that if you shoved on one point, the other point moved exactly the same. From my God-like perspective, all you did was shove the ring a bit. You, on your flat plane, see spooky action at a distance, because you're shoving one point and the other one is moving, too.

      Given enough time and experimentation with these points that keep appearing in your plane of experience as I keep shoving rings and perhaps even more complex objects through your plane, you might even be able to come up with some really complicated mathematics and physics that describe all this bizarre motion and behavior in your 2 dimensional world. To you, it all appears incredibly complex and horribly incomprehensible, even utter nonsense, but you can manage to describe it in such a way that is at least consistent with the weird behavior you keep seeing. To me, in my 3rd dimension, I'm just chuckling over all that hard work you're going to, because to me it's just a simple ring I'm shoving through your plane and watching you go batshit crazy trying to figure out what's going on.

      The point is simply that quantum physics appears bizarre to us because we are limited to experiencing 3 spatial dimensions and are forced to constantly move in a single direction on an axis of time. All the weirdness of quantum physics really just means that there are almost certainly many more spatial dimensions and more complete freedom of motion through time than what we are limited to experiencing. What you're seeing a lot of times is just the weirdness of seeing something that almost certainly "completely" exists in several more higher dimensions intersecting limited reality you are able to witness.

    12. Re:Heisenberg compensator ... by tnk1 · · Score: 3, Informative

      11 dimensions is M-Theory, but if you go by Loop Quantum Gravity, you can formulate it in 3 or 4 dimensions.

      There's really no theory that has "won" yet, so it is far too early to say there is a minimum number of dimensions.

      Like you suggest, I believe that the "magic" of quantum effects would be a lot less "magical" if the objects in question could be described in at least one more dimension. The uncertainty principle is likely uncertain because you can have almost identical looking 4-D slices in a 5-D space. It only breaks down when you realize that certain objects or processes are prone to change much more extremely in higher-numbered dimensional space. So, if you fail to take 5-D into account, you can come up with a formula which seems to have two equally probable states, but in the end, of course, there was never any doubt.

      For some value of 'q' the cat is dead and for some value of 'q', the cat is alive. Our current state of science is that we have equations that work very well with objects that are less variant in the 5th dimension than photons or quantum scale objects/processes are. Just like when we assumed that stars and mountains never changed or things didn't evolve because those processes are far less variant in the time dimension than the typical human lifetime.

    13. Re:Heisenberg compensator ... by kassay · · Score: 2

      On my screen, the parent comment "The universe is under no obligation to make sense to a bunch of shaved apes." was ironically right above a 'Harry's Razors' ad.

  3. Consequences for quantum computing? by ralejs · · Score: 4, Interesting

    It'll be interesting to see what consequences this result will have on quantum computing. If the tipping point between the quantum and the classical world is something fundamental to physics and cannot be overcome, that means there is a limit to how big quantum computers can be. And if there is such a limit, will the largest possible quantum computers be any useful or does it mean that the whole field of quantum computing amounted to nothing?

  4. A flock of starlings by Anonymous Coward · · Score: 3, Interesting

    If you can't see the individual starlings, and can only see the flock, the flock behaves in a quantum manner. It jumps around, it can appear in two places at once, apparently traveling faster than light, it has probabilistic properties.

    So the tipping point, depends on our detection technologies. If we can't zoom in to see the individual starling then quantum behavior is "flock of bird" sized!

    Quantum physics does scale, you just need to realize that the 'flock' is the size that you can detect, and the reason you think it is one thing is because you can't detect half a thing. It's a function of the detector not the thing.

  5. Re:At What Frequency? by m.dillon · · Score: 3, Informative

    That is not a correct description. Lower frequency radio waves are no less 'quantum' or 'classical' than higher frequency radio waves. AM radios can penetrate objects primarily because they have a wavelength on the order of 400 meters (up to around 1 MHz), whereas FM radios have a wavelength of only a few meters (through around 100 MHz). The longer wavelength of AM effectively allows the radio wave to bypass even relatively large objects such as mountains.

    The same effect can be seen even within your house if you have a dual-band WIFI router. The 2.4 GHz band is able to penetrate walls and go around corners and reach the second floor far more easily than the 5 GHz band can.

    -Matt