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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.

5 of 83 comments (clear)

  1. 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 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.
    2. 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!).

  2. 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?

  3. 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.