Bell's Theorem: The Quantum Venn Diagram Paradox

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Published 2017-09-13
Featuring 3Blue1Brown
Watch the 2nd video on 3Blue1Brown here:    • Some light quantum mechanics (with mi...  

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This video is about Bell's Theorem, one of the most fascinating results in 20th century physics. Even though Albert Einstein (together with collaborators in the EPR Paradox paper) wanted to show that quantum mechanics must be incomplete because it was nonlocal (he didn't like "spooky action at a distance"), John Bell managed to prove that any local real hidden variable theory would have to satisfy certain simple statistical properties that quantum mechanical experiments (and the theory that describes them) violate. Since then, GHZ and others have managed to extend the theoretical work, and Alain Aspect performed the first Bell test experiment in the late 1980s.

Thanks to Vince Rubinetti for the music: soundcloud.com/vincerubinetti/one-two-zeta

And thanks to Evan Miyazono, Aatish Bhatia, and Jasper Palfree for discussions and camaraderie during some of the inception of this video.

REFERENCES:

John Bell's Original Paper: inspirehep.net/record/31657/files/vol1p195-200_001…

Quantum Theory and Reality: www.scientificamerican.com/media/pdf/197911_0158.p…

"What Bell Did" By Tim Maudlin: arxiv.org/pdf/1408.1826

Bell's Theorem on Wikipedia: en.wikipedia.org/wiki/Bell%27s_theorem

2015 experimental confirmation that QM violates Bell's theorem: arxiv.org/pdf/1508.05949.pdf
journals.aps.org/prl/abstract/10.1103/PhysRevLett.…

Bell's Theorem without Inequalities (GHZ): dx.doi.org/10.1119/1.16243

Kochen-Specker Theorem: en.wikipedia.org/wiki/Kochen–Specker_theorem

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Created by Henry Reich

All Comments (20)
  • @dannymendiola
    Love the peaceful music while you light my brain on fire
  • @ChaseCrossing
    I heard they're patching this in the universe v2.0 update
  • I saw this video when it first came out and thought it was really interesting, now I’m in college and just finished taking classes over quantum physics and laser physics and I actually recognize/understand a lot of the concepts and math here which is so cool to me! Thanks for inspiring younger me to go into physics!
  • @diverse1469
    I loved this video and occasionally watch it. It is also the subject of the 2022 Nobel physics prize and one of if not the best explanations of it I've seen so far. By the way, the contributor of the last paper shown as an example of the studies about the bell theorem is the Nobel Laurette Anton Zeilinger. I really hope this video gets more watch man, thanks a lot!
  • @user-wg8hq7nw5c
    Universe: can we have math please? Quantum physics: we have math at home Math at home: 15+15=50
  • There is an 85% chance you will not understand this video if you watch it once, and a 100% chance if you watch it twice
  • @mickmack8026
    I only understood 15% but I'll understand 50% when I forgot half of it.
  • @Bless-the-Name
    IRS: Your accounts don't balance. Company: Turn the Balance Sheet 45°
  • What if the filters are changing the orientation photons that pass through them? A photon that passes through A but does not pass through C might suddenly be able to pass through C after passing through B if B changes the orientation of the photon just enough to make it able to pass through C.
  • @user-xn8wg6yw7g
    This is much better than other explanations because it explains the main idea. Take this video as a great heuristic explanation. It doesn't pay to get stuck on the details of polarization filters and what could be going on inside them... What these creators do so well: They try to make the whole scenario intuitive rather than stuffing everything into equations and relying on mysterious integral tricks and suddenly pull a rabbit out of a hat. That's the style I was used to from undergrad physics. Thank you, keep up the great work.
  • @MAMAJUGO
    Can't wait for next year's show: hourphysics
  • The second time watching this video, I tilted my head 90 degrees -- and forgot everything.
  • @GPCTM
    2:05 "photons are waves". Well, that settles it.
  • @sergevalet
    I am so not used to Grant rushing his usually slow narrative in order to keep up with Henry. What a great video!
  • @iquemedia
    This is like 17 episodes of minutephysics in 1
  • @Jacob-yg7lz
    I'm in a superposition of understanding this
  • @TheJorgVideos
    I've got some kind of issue at 5:00 We have the 45° blocking 50% of light, no problem here. Then the 22.5° appart ones above: In the video we have 100% light comming in (btw 100% light isn't comming out of A but for the sake of the example lets consider it 100 for the rest of the manipulation), then 85% out of lens B, to finaly 70% out of C. 100-15-15=70 But as far as I understand, the light filtering probability happens independently between two filters and not a whole set. Therefore the calculation should be 100% - 15% between A and B Then again 100% (of what is left after B) - 15% between B and C (A and B have 22.5° diff and same for B and C) Since we know 85% is left after going through B we can extrapolate the result by converting the 15% of 100 to a "15%" of 85%: 15*85 / 100 (cross product) 12.75 So in the end we have 100-15-12.75 = 72.25% left out of C Even though A and C have 45° diff, because of the presence of B at 22.5° the filtering probability is "reset" and therefore has a different result than just going through C directly. This is my personal understanding and could be flawed. I haven't seen the rest of the video as posting this so I don't know yet if this is addressed later on.