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Science

Quantum Physics Just Got Less Complicated 197

wabrandsma sends this news from Phys.org: Here's a nice surprise: quantum physics is less complicated than we thought. An international team of researchers has proved that two peculiar features of the quantum world previously considered distinct are different manifestations of the same thing. The result is published 19 December in Nature Communications. Patrick Coles, Jedrzej Kaniewski, and Stephanie Wehner made the breakthrough while at the Center for Quantum Technologies at the National University of Singapore. They found that wave-particle duality is simply the quantum uncertainty principle in disguise, reducing two mysteries to one.
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Quantum Physics Just Got Less Complicated

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  • by narf0708 ( 2751563 ) on Friday December 19, 2014 @12:18PM (#48634743)
    Seriously guys, we need to drop the copenhagen interpretation already. Pilot-wave theory [quantamagazine.org] eliminates the need for quantum mysticism.
    • by Empiric ( 675968 ) on Friday December 19, 2014 @12:39PM (#48634987)
      In its current, immature state, the pilot-wave formulation of quantum mechanics only describes simple interactions between matter and electromagnetic fields, according to David Wallace, a philosopher of physics at the University of Oxford in England, and cannot even capture the physics of an ordinary light bulb. "It is not by itself capable of representing very much physics," Wallace said. "In my own view, this is the most severe problem for the theory, though, to be fair, it remains an active research area."

      A little early to "drop it", it seems.
      • True, much work on it does need to be done before it is nearly as mature as the traditional interpretation.
        • True, much work on it does need to be done before it is nearly as mature as the traditional interpretation.

          In other words, it's voodoo mysticism which isn't useful for anything, and the author may or may not be reaching to make his theory look sound?

          Because the GP kinda makes it sound like healing crystals, and generally not very useful at all.

          When there is "much work to do" on your pet theory before it can explain a lightbulb, maybe your theory is worthless?

    • Well, I remember Scott Aaronson saying de Broglieâ"Bohm's pilot wave theory requires exponential resources to simulate even with a quantum computer. Ergo even if it makes some things easier to understand it's not generally the most useful way to think about QM and arguably in some sense can't be the way Nature does what it does.
      • by holmstar ( 1388267 ) on Friday December 19, 2014 @12:56PM (#48635165)

        and arguably in some sense can't be the way Nature does what it does

        citation needed.

      • by mothlos ( 832302 )

        even if it makes some things easier to understand it's not generally the most useful way to think about QM

        Engineers use Newtonian gravity as the basis for their equations because they are more practical than using relativity. Even if this theory were to turn out to better describe the universe, actual work would get done using simpler, good-enough probabilistic equations instead of the deterministic ones, but that wouldn't change the fact that the new theory better explains the total body of observations we have.

        and arguably in some sense can't be the way Nature does what it does.

        Why would this be the case? Chaotic systems as a class are extremely difficult to calculate, but we

    • But surprised they don't use the correct word: (a)ether [just-think-it.com].
    • by Cyberax ( 705495 ) on Friday December 19, 2014 @01:43PM (#48635641)
      No, it doesn't eliminate the dualism. Pilot wave theories are a subtype of hidden variable theories and thus were proven wrong by Bell inequalities. The fact that some fluid dynamics systems behave kinda like quantum systems (and only qualitatively so!) means nothing.
      • Local hidden variable theories were dis-proven, but why would a pilot wave be considered local to the particle? It's a property of space-time, not the particle itself.
        • by Cyberax ( 705495 )
          It doesn't matter. A pilot wave is a type of a hidden state, in such theories particle take a unique way determined by a pilot wave.

          Think about it - how can a pilot wave communicate which way a particle must take without going backwards in time (i.e. violating the Lorentz invariance)? Imagine that you have a classic two-slit single electron interference experiment. Suppose that the pilot wave theory is true - in this case a pilot wave interferes with itself and electron chooses one path and ultimately hit
        • by sconeu ( 64226 )

          Bell showed that Von Neumann's disproof of local hidden variable theories was flat out wrong.

          My understanding is that hidden variables theories can be made to work if reality is non-local. And given that quantum entanglement appears to be non-local, hidden variables should be able to work.

    • Seriously guys, we need to drop the copenhagen interpretation already. Pilot-wave theory [quantamagazine.org] eliminates the need for quantum mysticism.

      That theories been prove wrong hundreds of times now.
      The simplest explanation of why it's wrong is that it's Deterministic. i.e. it's part of the "Clockwork universe" and if that's true, then you do not have free will and we should all just throw in the towel now... oh wait, that's right, we don't have a choice. Don't worry, I know it's not your fault that you posted this though, it wasn't up to you!

      Determinism = fail

      • by ultranova ( 717540 ) on Friday December 19, 2014 @04:48PM (#48637585)

        The simplest explanation of why it's wrong is that it's Deterministic. i.e. it's part of the "Clockwork universe" and if that's true, then you do not have free will and we should all just throw in the towel now...

        While we're at it, the Second Law of Thermodynamics must be wrong because I'd like a perpetual motion machine and conservation of momentum must get temporarily suspended when someone's about to be run over by a truck.

        Also, determinism doesn't conflict with free will. Determinism is a concept in physics and free will is a concept in law and philosophy. If you try to contrast them, you'll end up equating free will with randomness: you didn't write your message based on your beliefs which you've formed based on your character and experience (since that would be deterministic), but rather it's the equivalent of "cat /dev/random | strings".

        Determinism = fail

        No, but even if it was, it in no way would disprove it.

      • by epine ( 68316 )

        Determinism = fail

        With entanglement, we have an FTL coupling that can't be used to convey classical information.

        Why can't we have a similarly knackered stripe of determinism, one which can't be used to shatter the illusion of free will? This would be a kind of determinism where even if you sort of know it's there, it makes no damn difference to your interpretation of local space.

        Think big, grasshopper, think big.

    • Seriously guys, we need to drop the copenhagen interpretation already.

      Sorry, the geniuses who created quantum mechanics were right the first time. The fact that you find it philosophically objectionable doesn't make it any less valid.

    • by Khashishi ( 775369 ) on Friday December 19, 2014 @04:25PM (#48637361) Journal

      There's no mysticism in quantum mechanics. It's pretty simple and mathematically consistent. All of the mysticism comes from popularizations of quantum mechanics. Bohmian mechanics is an unnecessary complicated interpretation of the same physical models.

      • Exactly.
        QM is a solid, reliable and well-tested theory of subatomic interactions, but only when expressed mathematically.
        As soon as someone tries to translate the math into words, everything falls apart because words are always vague and have multiple meanings.
  • by Translation Error ( 1176675 ) on Friday December 19, 2014 @12:18PM (#48634745)
    Of course! This clears up everything! Now I understand quantum physics completely!
  • by Anonymous Coward

    I thought that Pilot Wave Theory answered this "uncertainty"?

    • Re:Pilot Wave (Score:4, Informative)

      by Immerman ( 2627577 ) on Friday December 19, 2014 @12:41PM (#48635003)

      There is a difference between having a competing theory, and proving that two broadly recognized phenomena are actually mathematically equivalent.

    • As I understand it, Pilot Wave theory is a hidden variable theory, and Bell's Theorem [wikipedia.org] says you can have hidden variables or locality (meaning no action-at-a-distance), but you can't have both, and most physicists really don't like the idea of giving up locality.
  • by pla ( 258480 ) on Friday December 19, 2014 @12:19PM (#48634769) Journal
    Wow, loving all the ACs calling this obvious, who clearly didn't even make it to the abstract! "Such wave-particle duality relations (WPDRs) are often thought to be conceptually inequivalent to Heisenberg's uncertainty principle, although this has been debated."

    Clearly, all you armchair physicists need to set those ivory-tower morons straight!
  • Can we say that this new discovery is a Quantum Leap? What do you think, Al?

  • by barlevg ( 2111272 ) on Friday December 19, 2014 @12:34PM (#48634941)

    Here we show that [wave-particle duality relations] correspond precisely to a modern formulation of the uncertainty principle in terms of entropies, namely the min- and max-entropies. This observation unifies two fundamental concepts in quantum mechanics. Furthermore, it leads to a robust framework for deriving novel WPDRs by applying entropic uncertainty relations to interferometric models.

    So they're looking at it in terms of entropies, and when they do, it resolves a debate about whether WPDRs are equivalent to the Uncertainty Principle AND generates new WPDRs.

  • I'd love to read a real comment (yeah, I know, it's almost like I'm new here) from someone who is actually capable of understanding the math here. It would be great to see a reasonable discussion on the actual implications here.

    As to people saying "that's obvious" -- what you can intuit and what you can prove are not the same thing. The only thing prove by a "that's obvious" comment is that the person posting it doesn't have a clue.
    • by Jamu ( 852752 ) on Friday December 19, 2014 @12:56PM (#48635159)

      A quantum state of position can be written as a superposition of a momentum states; the position is certain and the momentum is uncertain.

      A quantum state of momentum can be written as a superposition of position states; the momentum is certain and the position is uncertain.

      That's the duality and the extremes of the uncertainty principle. The mathematics can also show more generally, that the uncertainty in position and momentum is always more that a certain value (Planck's constant).

      These things follow directly from the axioms of Quantum theory, Hilbert spaces and any two non-commutative operators. So I really don't see how Quantum Physics "just got less complicated". It's the same as it's always been. Although I've not read the paper yet, maybe that makes more sense.

    • by Anonymous Coward

      Really, really simplified form from one of the linked articles.

      Some specialists in quantum information theory (not their term, but it fits) found that a mild variation of their extremely specialized mathematical models could be used to describe the wave-particle duality concept as another form of the quantum uncertainty limitation.
      The classic quantum uncertainty argument is that velocity and position are related features that cannot be known beyond a certain level of combined precision. As you test harder

    • by hweimer ( 709734 ) on Friday December 19, 2014 @02:19PM (#48636003) Homepage

      I just had a brief look at the published version of the paper. Unless you work on fundamental aspects of quantum information theory, the actual implication is that some old debate that took place back in the 90s has been resolved. As others have already pointed out, the relationship between uncertainty relations and wave-particle duality intuitively makes sense, but actually coming up with a mathematical proof that the two concepts are equivalent to each other is certainly a non-trivial amount of work. However, this paper does not significantly change our understanding of quantum physics, nor does it allow us to magically find an efficient way to simulate quantum physics on classical computers. It will also not change the way quantum physics is usually taught, as wave-particle duality basically plays no role there (and uncertainty relations are mostly a side remark).

      Also, notice that the paper has been published in Nature Communications. Usually, this means that the paper was rejected by Nature Physics (or any other of the "Nature Something" journals), so the authors sent it there instead (BTDT). So we probably have at least an editor (and maybe some referees) who thought that the paper was not as sexy as the press release seems to imply.

  • by 140Mandak262Jamuna ( 970587 ) on Friday December 19, 2014 @12:53PM (#48635125) Journal
    If something gets simpler, the entropy of the universe decreases. It can't happen. It is the law, everything should get more and more complicated as time goes by. Why, the next generation will have easier time to pass Quantum Mechanics I PH304 MWF 10:00-11:30 than I did? Would not stand for it.
  • I'm not a physicist - and I worked most of this out myself years ago - cf. http://slashdot.org/journal/35... [slashdot.org]

    • What's news is that

      an international team of researchers has proved

      etc.

      • There's one huge problem with the notion of proof in physics: You never know when your theory might be superseded. You can't make a generalising statement in physics which is essentially formally proven since there is always a possibility that it would be overtaken by a newer one.

        So, your cite from tea is pretty meaningless. A 'proof' of this order is noting less than a revised theory, hence my OP

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