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How does QE explain more mismatches in Bell's test at wider angles?

  1. Jun 19, 2012 #1
    While I think that the phenomena of Quantum Entanglement exists, it's real; it's interesting to understand more about it.

    How does QE/QM explain more mismatches (relatively to simple probability calculations) in Bell's test at wider angles?

    Or alternatively: Why does/would QE result in lower matches (rather than higher matches) at wider angles?

    QE = quantum entanglement

    In Bell's Tests, we get the following results:

    ----------------Per QM/Actual Experiment
    ----------------Mismatches (out of 100)

    at (0,30) --------------- 25
    at (-30,0) -------------- 25
    At (-30,30) ------------- 75

    Per LHV the result at (-30, 30) should have been 50.

    Thus we are getting 25 more mismatches. No LHV theory can explain this, however QM can explain this mathematically and conceptually.

    What is the conceptual explanation per QM?

    Is it something like below?:

    Since the two entangled photons are somehow "connected/entangled" the chances/probability of a match will decrease because both the photons have to satisfied "in a connected manner" (i.e. both have to encounter "good" angles in a "connected/entangled manner").

    or to take another example:

    Rating a movie as Liked or Disliked

    Case A - Two friends watch a movie and communicate with each other prior to rating the movie. And the friends have the ability to influence each other's rating.

    Case B - Two individuals watch a movie and never communicate with each other and rate a movie.

    There are two parts here:

    Part 1 -- no theory (other than QM) can explain this
    Part 2 -- QM can explain this
    Last edited: Jun 19, 2012
  2. jcsd
  3. Jun 19, 2012 #2

    Ken G

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    Gold Member

    I think the point is, the entanglement allows for correlations that cannot be mediated strictly with information that is "carried with" each particle. This gives us two choices of interpretation: either information about the system retains a holistic or global character (also called "contextuality"), or else information can be exchanged superluminally. The first case is interpreted as breaking "realism", and the second is interpreted as breaking "locality". Choose your poison.
  4. Jun 19, 2012 #3
    Thanks Ken G. Agree with the part you wrote above.

    To understand this further -

    Let's say the real test (i.e. the Bell's experiment) gave the result P(-30, 30) = 35 .........(instead of 75)

    (we are assuming reality/universe is such way)

    i.e. mismatches are lesser (at wider angles) than that predicted by probablity laws

    Could we, even in such a case (universe), apply the same logic and, say that -- .....we are either breaking "realism" or "locality"?
    Last edited: Jun 19, 2012
  5. Jun 19, 2012 #4
    I think I got the answer. The mismatches are not always more.

    After the 90 degree difference the trend reverses in the graph.

    Mismatches are actually lesser (between 90-180 degrees) than that predicted by linear/probability curve as can be seen in the graph below.

    0-90 = mismatches more than that predicted by probability/linear
    90-180 = mismatches less than that predicted by probability/linear
    180-270 = mismatches less than that predicted by probability/linear
    270-360 = mismatches more than that predicted by probability/linear


    Last edited: Jun 19, 2012
  6. Jun 19, 2012 #5


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    Science Advisor
    Gold Member


    Good stuff!

    A minor note: the zero crossings on your graph should be every 45 degrees rather than 90. See the link, this is on a scale of 0 to 1:



    EDIT: Oops I mean every 90 degrees rather than 180.
    Last edited: Jun 19, 2012
  7. Jun 19, 2012 #6
    thanks DrChinese. So, is the logic in post #4 above (by and large) correct then?....

    well said DrChinese, you mean the zero "difference" between QM and Linear (and not the zero correlation) crossings? good catch, thanks for pointing that out.

    so in the diagram (in post 4) should there be 8 "flaps/convex/Ds" instead of 4?
    Last edited: Jun 19, 2012
  8. Jun 19, 2012 #7
    The graph (in post 4) is showing at 90 degrees only. I think your earlier, prior to the edit, was correct....
    Last edited: Jun 19, 2012
  9. Jun 19, 2012 #8

    From that I get the impression the case is saying that entangled particles only exist if they encounter the appropriate angles to show the QM mis-match rate. This doesn't seem correct.

    QM can PREDICT the right outcomes. Any future theory that supercedes QM will need to include these predictions.
  10. Jun 19, 2012 #9
    No I did not mean that. Sorry if I did not put this better.

    What I mean is - (and maybe there is a better way to put this) -

    Entangled particles as a single unit "decide" (by looking at both the angles) whether to go or no-go.

    in contrast to -

    Two un-entangled particles (with the supposed local hidden variables) that "decide" separately without having to "communicate" with each other.

    agreed, not disputing that.
  11. Jun 19, 2012 #10
    Good points - and I start to think that such summaries are misleading (wrong).
    More precise would be, I think (but if I'm wrong then I would like be corrected!):

    Part 1 -- this is incompatible with any reasonable "local" theory (=without magic or "spooky" effects at a distance)
    Part 2 -- QM predicts this, but does not (and perhaps cannot) explain it.

    As a matter of fact, it all started out with attempts to explain the predicted QM effects with "local realism".
  12. Jun 20, 2012 #11
    Agreed, your edits are valid, Harrylin. Well corrected.

    there is a Minor addition - QM can predict somethings but not others.

    For example:
    Can predict

    if a (bunch) of photon will form an interference pattern or not

    Cannot predict
    where the photon will land on the screen

    Thus if we do no-which-way, QM can predict that the photon will land one of the fringes but it cannot predict which fringe and its position on the screen/fringe. As per QM the position, on the screen, can never be predict (with100% accuracy) you can only assign probabilities to it.
    Last edited: Jun 20, 2012
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