Quantum Eraser | Quantum Mechanics ep 4

Category : Randomness
Quantum Eraser | Quantum Mechanics ep 4by wpjljron.Quantum Eraser | Quantum Mechanics ep 4I explain the set up of the Quantum Eraser experiment! Episode 2 is here: http://youtu.be/pTX81MwxgSs or watch all the previous videos on Quantum here: https…

I explain the set up of the Quantum Eraser experiment! Episode 2 is here: http://youtu.be/pTX81MwxgSs or watch all the previous videos on Quantum here: https…


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25 Responses

  1. Alessandro Lehmann7 June, 2014 at 9:13 pm

    But what would happen if in the slit experimente we put three holes, and
    just measure if the electrons (or photons) had gone to one of the
    three?This way we would have some information about their trajectory, but
    not all of that. Would it have the wave interference shape just around the
    holes we didn’t measure?

  2. obed rodriguez2 June, 2014 at 8:15 pm

    How are photons entangled? Do they just come like that? Or what?

  3. sodom874 May, 2014 at 6:46 am

    I have seen the explanation for the double slit experiment but I still
    don’t understand the part where a single photon (unmeasured) passes through
    the first screen and interacts with itself to contribute to the
    interference pattern (this meaning it is a wave); but then leaves a single
    localized point in the second screen (meaning it is a particle). So, does
    this mean it was behaving as a wave the whole time up until the point it
    crashed with the second screen and its photoelectric measurement made its
    wave function collapse and become a particle at a random point of the wave
    trajectory it had? hence you only see a dot in the measurement and not
    scattered light (as a wave). The first part of the video (0:43) made me
    think this, because it says that before measurement the photon is a wave
    (not superposition) and during measurement it is a particle. Am I correct?

  4. Harold Wimberly29 April, 2014 at 3:40 am

    Question, how do you know a machine made a measurement of the photons
    polarization if a conscious observer never looked at the results? Also,
    aren’t measuring devices created by conscious beings? How can you separate
    the measuring device from the conscious observer that created the measuring

  5. Swanky Butters28 February, 2014 at 10:25 am

    It feels like quantum phenomenon has something to do with the conservation
    of energy. Why would something not pick a state to be in when no one is
    looking? Maybe to save energy.

  6. vinm3006 February, 2014 at 2:43 pm

    Hi, the retina can detect single photons but there is a suppression system
    that the brain only becomes aware of say 10 photons arriving.
    Frogs have eyes that can detect single photons.

  7. 991woot11914 January, 2014 at 6:17 am

    Big question I have, does the interference pattern not happen even if A is
    measured after B has gone through its course?

  8. Flamy Fero7 January, 2014 at 11:55 pm

    One does not simply watch one episode of this…

  9. Phllip Mclennan28 December, 2013 at 4:02 pm

    Then there’s delayed choice, complementarity etc. If all this confused
    Einstein and others, I don’t feel so bad. 

  10. Adriano Me26 December, 2013 at 8:48 pm

    How can we entangle two electrons in a practical way.

  11. FunkyLoiso22 December, 2013 at 1:36 pm

    Please, can you explain why this experiment cannot be used for faster than
    light information transfer? Say we created a bunch of entangled photons.
    Sender has photons A and Receiver has corresponding photons B. Then at some
    appointed time Receiver starts to perform the experiment from the video. If
    Receiver gets the interference picture that means photons from A were not
    measured, and vice versa. Receiver can even measure the average percentage
    of A photons that were measured! So where is the catch? (:

  12. Ben Gardner18 December, 2013 at 5:03 am

    This contradicts so much that I have learned in school. The main thing that
    I am confused about is that you said that photons(light) were either a
    particle or a wave. According to Einstein’s theory about wavicles, light is
    always both a particle and a wave at the same time.

  13. Ethan Massicotte17 December, 2013 at 3:42 am

    Doesn’t a conscious observer always have to perceive the result, either
    implicitly or explicitly? 

  14. somewony15 December, 2013 at 1:35 pm

    That is truly one of the most clever experiments i’ve ever heard of!

  15. Mark Sullivan13 December, 2013 at 6:26 am

    I may not be understanding correctly but what happens if we send B through
    first and then quickly after measure A to see if it agrees with B results?
    Since B is already completed the experiment and we already marked the
    outcome it wouldn’t be possibly for it to change what already happened. Or
    is it not possible to measure A after B hits? Maybe you did talk about this
    in the video and I missed it, sorry about that!
    P.S. i’m loving these videos though, very helpful!

  16. anoop johnson10 December, 2013 at 6:19 am

    Let me ask u one question. I think it can solve all the confusions. I
    believed in science and now science is cheating me and pushing me to
    believe some thing, which my brain cant take. so the question is


  17. KoruptBD7 December, 2013 at 9:57 pm

    So, does this mean that particles have either telekinetic abilities or
    cellphones on them? o.o How else would a particle connect with another
    particle to say that he’s found out =|
    If only there was a way to block that communication, all this tricking
    wouldn’t be needed then x_x

  18. TheSquarecow5 December, 2013 at 6:11 pm

    Aaand another question: Shouldn’t the quarter-wave plates count as
    detectors themselves? You could see them as objects that detect photons and
    report this detection by sending polarized photons… where is the
    difference to your actuals detectors (the blue box) that send out
    electrical impulses when they detect photons?

  19. TheSquarecow5 December, 2013 at 5:54 pm

    Couldn’t the experiment be done just as well without the quarter-wave
    plates, by just measuring the horizontal/vertical polarity of the photons
    as they hit the detector?

    And -bonus question – can a single photon even *have* circular polarity? I
    understand circular polarity as two waves, one horizontal, one vertical,
    where one is delayed by a quarter wavelength. If you do a vector addition,
    you’ll get a corkscrew-like curve. Wouldn’t that require two photons? 

  20. Shashank Joshi5 December, 2013 at 12:58 pm

    correct me if i’m wrong, the purpose of entanglement here was to observe
    photon B indirectly by observing photon A instead. (which fails because the
    universe is a conniving little piece of work like my neighbor)

  21. dixit05244 December, 2013 at 6:13 pm

    My god …you are another Schrodinger…..you explain so so so well…love
    you….you have cleared my decade long mis-concepts……

  22. Gabo Martinez3 December, 2013 at 2:50 am

    It’s amazing to think that measuring A is really enough to force B to
    decide a state and behave like a particle

  23. Gabo Martinez3 December, 2013 at 2:47 am

    the entanglement fact will be interesting to be explained

  24. Nillie30 November, 2013 at 11:30 pm

    This is just too weird to decide, because how conscious does an observer
    have to be in order to collapse superpositions? Let’s go back to
    Schrödinger’s cat metaphor: There are two “objects” in the box that could
    measure what happens without us opening it – the geiger counter and the
    cat. Does the geiger counter collapse the superposition, and if it doesn’t,
    does the cat? And does it matter whether the cat was asleep? (Cats sleep up
    to 20 hours a day, so this is very likely, especially if it had time to
    settle down before the experiment started.)

  25. Samuel Sandeen28 November, 2013 at 11:04 pm

    The QM flavor I find the most plausible is the one which says that there is
    no measurement collapse. This flavor instead says that everything is in
    superposition all the time but you can associate two superpositions and
    once two object’s superpositions are associated they both appear collapsed
    to each other.

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