The Triple Slit Experiment:

Discussion in 'General Science & Technology' started by paddoboy, Jan 6, 2017.

  1. paddoboy Valued Senior Member

    Messages:
    21,225
    Physicists detect exotic looped trajectories of light in three-slit experiment
    January 6, 2017 by Lisa Zyga feature
    Nature Communications" style="color: rgb(49, 61, 87); outline: none 0px; font-weight: 700;">

    Please Register or Log in to view the hidden image!


    The red path shows an exotic looped trajectory of light through a three-slit structure, which was observed for the first time in the new study. Credit: Magaña-Loaiza et al. Nature Communications
    (Phys.org)—Physicists have performed a variation of the famous 200-year-old double-slit experiment that, for the first time, involves "exotic looped trajectories" of photons. These photons travel forward through one slit, then loop around and travel back through another slit, and then sometimes loop around again and travel forward through a third slit.

    Interestingly, the contribution of these looped trajectories to the overall interference pattern leads to an apparent deviation from the usual form of the superposition principle. This apparent deviation can be understood as an incorrect application of the superposition principle—once the additional interference between looped and straight trajectories is accounted for, the superposition can be correctly applied.

    The team of physicists, led by Omar S. Magaña-Loaiza and Israel De Leon, has published a paper on the new experiment in a recent issue of Nature Communications.




    Read more at: http://phys.org/news/2017-01-physicists-exotic-looped-trajectories-three-slit.html#jCp
     
    danshawen likes this.
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. paddoboy Valued Senior Member

    Messages:
    21,225
    http://www.nature.com/articles/ncomms13987


    Exotic looped trajectories of photons in three-slit interference

    Abstract

    The validity of the superposition principle and of Born’s rule are well-accepted tenants of quantum mechanics. Surprisingly, it has been predicted that the intensity pattern formed in a three-slit experiment is seemingly in contradiction with the most conventional form of the superposition principle when exotic looped trajectories are taken into account. However, the probability of observing such paths is typically very small, thus rendering them extremely difficult to measure. Here we confirm the validity of Born’s rule and present the first experimental observation of exotic trajectories as additional paths for the light by directly measuring their contribution to the formation of optical interference fringes. We accomplish this by enhancing the electromagnetic near-fields in the vicinity of the slits through the excitation of surface plasmons. This process increases the probability of occurrence of these exotic trajectories, demonstrating that they are related to the near-field component of the photon’s wavefunction.
     
    danshawen likes this.
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. danshawen Valued Senior Member

    Messages:
    3,942
    Awesome. Makes sense though. Femtosecond cameras can actually see around corners. Same effect.
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. Confused2 Registered Senior Member

    Messages:
    416
    From http://www.nature.com/articles/ncomms13987
    Compare with a 'normal' double slit setup where the slit widths are greater than wavelength of the light used (example 90μm with 450nm light) and a slit separation of (say) 1mm.

    Using the same light while reducing slit width by a factor of 50 (far less than a wavelength) and decreasing the slit separation by a factor of 50 mighty well create a 'new' experiment - how much relevance (if any) it has to splitting a beam into two paths and bringing the paths back together - is unclear to me.

    After optimising for exotic effects it seems exotic effects are found.[/quote][/quote]
     
  8. Q-reeus Valued Senior Member

    Messages:
    2,497
    Tend to agree. Plasmon resonance becomes significant - so in effect the slit pattern itself has morphed. Expect some controversy over this one.
     
  9. DaveC426913 Valued Senior Member

    Messages:
    5,979
    Can this be seen as corroborating evidence of the Feynman-like "all possible paths" physics?

    Please Register or Log in to view the hidden image!

     
  10. paddoboy Valued Senior Member

    Messages:
    21,225
    My knowledge is limited on this stuff, but that's the first thought I had....Feynman's "Sum Over Histories"
     
  11. DaveC426913 Valued Senior Member

    Messages:
    5,979
    Everyone's knowledge is limited on this stuff.

    Please Register or Log in to view the hidden image!



    If you think you understand it, you don't understand it.
     
    Last edited: Jan 7, 2017
    paddoboy likes this.
  12. Q-reeus Valued Senior Member

    Messages:
    2,497
    'Looping Feynman paths' as explanation seems terribly contrived to me. Once you acknowledge surface plasmon resonance is the real explanation, why try and fit that to something very different? It's even bending things badly to talk of 'looping near field paths', since plasmons are coupled photon-electron quantum objects and the photon part can't be separated. Might as well claim that a looping piece of optical fibre is an example of a looping Feynman path.
     
  13. karenmansker HSIRI Banned

    Messages:
    638
    Before anyone 'jumps-the-gun' and attaches the term "Loop Theory" to this phenomenon . . . be advised that I have already adopted the term 'Loop Theory' in some of my more obscure writings (HAHA!)
     
  14. karenmansker HSIRI Banned

    Messages:
    638
    Perhaps you noticed the collaborative link at the bottom of the article - this has already been considered?
     
  15. Q-reeus Valued Senior Member

    Messages:
    2,497
    Probably nowhere near as tasty and popular (unfortunately) as another form of loop: http://www.frootloops.com/
     
  16. karenmansker HSIRI Banned

    Messages:
    638
    I have a question . . .If this "observation" actually occured, how did the experimenters determine/'detect' that the path was 'forward' thru one slit, then 'back' thru the second slit, then again 'forward' thru the third slit? It looks (to me) that they based their 'observation' on probablility of superposition, and NOT on actual detectible measurement.
     
  17. karenmansker HSIRI Banned

    Messages:
    638
    . . . that would be . . . the "Froot Loop Theory", I'd suppose . . . HAHA!
     
    Q-reeus likes this.
  18. Q-reeus Valued Senior Member

    Messages:
    2,497
    Yes there would afaik be no way to directly probe the slit region itself (doing so would obviously drastically modify the result anyway). So it was all up to matching the altered fringe pattern with the predictions for linear path only vs linear plus looping paths. My bet is it will be shown by someone else there is no need to invoke looping paths as interpretation.
    So as you hinted, just took a quick skim through the review ncomms13987-s2.pdf, and found this piece:

    "The work presented in this manuscript has used surface plasmons to demonstrate the so-called ‘looped trajectories’. The contribution of ‘looped trajectories’ to the interference could be tuned by exciting surface plasmons with different polarized light. This is purely classical optical phenomenon, which has been calculated by Maxwell equation and realized by using classical laser light. Although the authors have used heralded single photons as input, there is no difference between classical laser light and single photons in this work. The relevance of their work to the foundations of quantum physics is highly questionable. Therefore, I do not recommend it for publication."

    No expert on any of the QM involved, but have to agree with above dissenting opinion, based on the obvious fact of plasmon coupling actually doing the trick.
     
  19. DaveC426913 Valued Senior Member

    Messages:
    5,979
    The diagram is surely simpified for clarification. But the spirit may well be correct. It is surely born out by the math.

    You gotta remember, at this leaky edge of physcis, the math is the reality. The diagrams, and any other form of expalanation, are a poor shadow of the math.
     
  20. karenmansker HSIRI Banned

    Messages:
    638
    H-m-m-m . . . interesting . . . . "spirit" as in preconcieved notion? . . . . or hypothesis? . . . or as 'spirit' being a metaphysical attribute of their "experiment" - they 'believe' that their results should fit their suppositions and are therefore 'factual? . . . or, as in: "I hope to God (spirit) that our experiment produces more funding and wins us a (Nobel) prize!

    Yes indeed . . . . you pegged it correctly . . . the 'leaky edge' of physics . . . not the more 'solid ground' of the Scientific Method'!! . . . the math is the reality? . . . I guess so, however ."figures don't lie, but liars can figure!" (HAHA!)
     
    Last edited: Jan 8, 2017
  21. DaveC426913 Valued Senior Member

    Messages:
    5,979
    I mean the intent of the diagram. i.e. whether or not the picture is technically accurate.


    A similar example: the orbitals of electrons in an atom are complex. No diagram can easily and simply show what atoms "are", and any verbal description is wanting as well.

    The only correct, accurate representation of what atoms are doing is the equations themselves. The equations are the things.

    With slit experiments, the math is the behavior.

    I wish I could find the book where I found this reference.


    I think the rest of this is tongue-in-cheek.
     
  22. karenmansker HSIRI Banned

    Messages:
    638
    I agree . . . and I understood what you meant. In my posts, I usually indicate 'tongue-in-cheek' by TIC, or tic . . . sometimes I forget and just indicate same by a HAHA! . . . so goes the leaky edge of my brain! (TIC, tic, HAHA!). BTW: Can you 'show' me a math equation that accurately describes the successive paths of electrons around atomic nuclei? (TIC).

    I disagree. Equations are NOT things, other than graphical and numeric descriptions [not unlike ancient hieroglyphics ]. Re: Slits - Math is NOT the behavior - only the mathematicians' descriptions of what they believe is the behavior. BTW: I believe I can show the behavior of what atoms are doing without equations - a blackboard, some chalk, and a knack for explaining (via understandable analogy, mostly) to others is all that is required. In the current environment of 'cyberspace', I'd guess that posting a good animation/video would do fine. One does NOT need be be a mathematician to visualize how the universe works! Albeit, in this era, math appears to be the 'accepted' proof(s)

    Thanks for your discussions! [Note: No TIC here!]
     
  23. DaveC426913 Valued Senior Member

    Messages:
    5,979
    ...ish.

    You can sort of explain it. But all explanations will be lacking. Many words you use will have multiple meanings, such that a pupil could misconstrue or get a poor picture. All explanation you use will be analogies, be they simple or subtle.

    The only langauge that is capable of accurately and wholly describing it is the math.
     

Share This Page