Entanglement and Relativity

Discussion in 'Physics & Math' started by 1100f, Oct 26, 2015.

  1. 1100f Banned Registered Senior Member

    Messages:
    807
    Suppose that we have an entangled state. Let us say a particle with zero angular momentum that decays into two particles with spin half (Let us call them particles A and B). The spin in the z direction of these particles are measured at location with spacelike separation. Since the total angular momentum is 0, if one particle spin is measured to be Sz = +1/2, the other particle will necessarily be measured to be Sz = -1/2 and vice versa. Before the measurement the particles are in a superposition 1/sqrt(2) (|+-> - |-+>). Once one of the particles spin is measured, the other instantaneously collapses to the inverse spin. I want to describe the experiment as viewed in to different reference frame.
    Since the separation is spacelike, in different reference frames, the time ordering of the measurements can be changed.
    In the frame where A is measured before B, we perform a measurement of particle A spin. Suppose that we measure +1/2 (and a Stern Gerlach apparatus will pull the particle up). Because of the entanglement, particle B is now in a -1/2 spin state at the same time the measurement is performed on particle A.
    So, now particle B is in a -1/2 state and later (remember the measurement ordering) it gets down at the Stern-Gerlach apparatus.
    Let us describe the same experiment from another reference frame where the spin measurement of particle B is performed before the measurement of particle A.
    Since particle A has not yet been measured, there is no reason why particle B should be in the -1/2 state (there are no hidden variables). So there is no reason why its measurement should give -1/2.
    If the measurement gives indeed -1/2, then the later measurement of particle A spin will be +1/2 and I have no problem with that.
    However the measurement can also give a +1/2 state for the particle B spin and at the Stern Gerlach apparatus it should go up, and particle A will instantaneously collapse to -1/2 and will go down later at the Stern Gerlach apparatus.
    So, in one reference frame, particle A goes up and in the second frame it might go down and I have a problem with that.
    Can someone explain what is wrong in my reasoning.
    Please no crank. Thx
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. 1100f Banned Registered Senior Member

    Messages:
    807
    It seems that I am the crank in this post.
    Please remove it
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. danshawen Valued Senior Member

    Messages:
    3,950
    Entanglement only 'seems' faster than light. It is simultaneous in a manner that relativity does not address, because no energy propagates in order for entanglement states to flip.

    It is possibly the only type of energy interaction in this universe that does not require a second observer for a complete description of reality.

    I liked your description of the setup, even if you had second thoughts about the title. Gutsy, but don't do it unless, like me, you have nothing to lose.
     
    Last edited: Oct 29, 2015
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. 1100f Banned Registered Senior Member

    Messages:
    807
    Maybe I should have named this thread: "Enranglement and causality"
    What bothered me was that as long as I don't measure particle A, both particle A and B will be in a superposition state. As soon as I measure particle A, immediately particle B's wave function collapses to the value according to the measured value of A. It seems like the measurement at particle A causes the collapse of the wave function of particle B. It seems as if there is a cause (measurement of particle A) and an effect (collapse to the predicted value at particle B).
    But in some other reference frame (since particle A and B are spacelike separated), the effect can come before the cause
     
    danshawen likes this.
  8. danshawen Valued Senior Member

    Messages:
    3,950
    That's just because entanglement is in some ways "faster than light", and by a substantial amount. Relativity is not a complete description of anything other than bulk transport of energy or matter. Because the instant of "now" is more closely associated with a state of rest which applies to bound energy that is matter. This is not the same as a time interval, which proceeds at different rates depending on proximity to other bound energy and relative state of motion.
     
  9. danshawen Valued Senior Member

    Messages:
    3,950
    Or to put it another way, it is possible to set up the terminology in a human language for tossing a pair of dice, like this:

    With your eyes shut, and in the dark, toss a pair of unloaded dice and let them land on a sheet of acoustically isolated neoprene or foam so that it will not be possible for anyone to observe any energy exchanges or states of the rolled dice to determine what their final rest state or value will be.

    Are all of the faces of the pair of dice in a state of quantum superposition until and unless a light illuminates the faces and the value is read? I suppose you could say that. Could you invent a fancy mathematical description with or without more obscure meaning or application of basically the same situation? And just why would anyone wish to do that? Isn't "collapsing the wave function" just fancy pants terminology for observing the outcome?

    Are the dice "entangled"? In a manner of speaking, perhaps. if one of the faces is up, the other five are either down or to the side, and that is easily determined once the state of the upper face is known. It's pretty much the same way with entanglement. Entangled pairs of photons may be separated by great distances, but as soon as the state of one of them is known through direct observation, the state of the other one is also known. Flip the spin of the one you just observed without disentangling it, the other will one will surely flip, as though they are different aspects of the same object.

    Does that clear things up a little? Fancy names for this process like "collapsing the wave function" pretty much describes the same characteristic, does it not? Pauli's exclusion principle applies to entangled electrons in the inner shells of atoms. But electrons have mass (which would slow down the process relative to photons), and being in a bound structure means we can actually measure energy differences that result from this change of state.

    Relativity describes the dynamics of energy, bound energy, propagation and time dilation for speeds between "at rest" and c. Much more needs to be said about the "at rest" state, which for bound energy, seems to be some form of perfect rotation (and I don't actually know if it relates directly to c or not, but somehow I doubt that this process is that fast, or rather, is involved with entanglement that is actually much slower). But we already know that entanglement occurs without bulk transport of energy, bound or unbound, and that the state changes that occur do so at speeds that are, if not instant, at least 10k times c.
     
    Last edited: Nov 1, 2015
  10. 1100f Banned Registered Senior Member

    Messages:
    807
    Relativity is not only a description of "bulk transport of energy and matter", it is also a description of how different events are related in different reference frames.
    When a measurement is performed at particle A, the waveform collapses simultaneously at particle B.
    What is meant here by simultaneously? In which reference frame it should be simultaneous? If there separation is spacelike, the order of the two measurements is not even defined
     
    danshawen likes this.
  11. danshawen Valued Senior Member

    Messages:
    3,950
    I have.found this definition of simutanaeity to be lacking rigor. Since time runs at different rates everywhere and anywhere, and because entanglement has been shown to be "faster" than light in a vacuum, it makes no sense physically to talk about simultenaeity with respect to bulk transport of bound and unbound energy. If something faster than light in a vacuum exists, simultanaeity means something quite different than Minkowski conceived.
     
  12. 1100f Banned Registered Senior Member

    Messages:
    807
    Two events are simultaneous if they occur at the same time. If they do not occur at the same time, they are not simultaneous.
    If two events are not simultaneous, but they have a timelike separation, no matter what tLorentz ransformation you perform (as long it is a transformation frome one reference frame to another one that moves slower than c), the order of the events is preserved. when they have a spacelike separation, the order is not preserved anymore (this is why there is no causality between two events with a spacelike separation).
    So again, my question is: when particle A is measured, the collapse of the wavefunction of B is instanteneous. What I don't understand is instanteneous in what reference frame?
     
    danshawen likes this.
  13. danshawen Valued Senior Member

    Messages:
    3,950
    Neither do I, and that, basically, is my point, and also the point Minkowski missed because he was a mathematician, not a physicist.
     
  14. arfa brane call me arf Valued Senior Member

    Messages:
    7,731
    There are two concepts here, or questions. Simultaneity is only meaningful in respect of clocks which are synchronous; locality is the other, implied concept--events in the local reference frame of a clock are simultaneous for that clock.

    Locality doesn't "survive well", and has no place in a universal theory, because QM doesn't need it--locality of interactions is not part of the theory, although it is very convenient in experiments.
     
  15. FOLZONI Registered Senior Member

    Messages:
    129
    Dear arf,

    Greetings from a member a long time silent.

    Simultaneity in the whole universe irrespective of motion is the fundamental Galilean-Newtonian philosophical position necessary for science. I.e. time is objective. Space too is objective, existing independently of time and of matter. Only the Three Stooges (Fitzgerald > Lorentz > Poincare) then Einstein conjured up the notion of localism i.e. non-simultaneity - and you yourself rightly state that "Locality doesn't 'survive well' and has no place... because QM doesn't need it."

    Hence our conundrum is easily resolved.

    1) Entanglement is fundamental to QT (quantum theory) and has been repeatedly demonstrated by faster-than-light motion (& information transfer), violating Special Relativity (SR). I.e quantum theory is the genuine theory.

    2) SR is bunk, and so are its derivatives - GR, gravity waves, black holes, Big Bang etc. etc.

    FOLZONI

    PS: Moderators! Your editing facility on sciforums is now really good!
     
  16. brucep Valued Senior Member

    Messages:
    4,098
    Really? What makes you an expert in your own eyes? So far you sound like a scientific illiterate crank.
     
  17. FOLZONI Registered Senior Member

    Messages:
    129
    Dear Brucep,
    the answer is that the teachings of Gang of Four (Fitzgerald, Lorentz, Poincare and Einstein) lead to logical paradoxes when applied to physical situations. And that unlike so many others I bother to look at the wider implications of believing in theories, supposedly scientific, that engender such logical paradoxes!

    The Gang of Four's notions lead to the doctrine of Local Realism (Quantum Interpretation type A), a position repeatedly disproven by the demonstration of quantum entanglement (in favour of type B or type C interpretations, depending on one's philosophical stance). Unfortunately so many scientists are so entangled by the beliefs in special relativity (SR) that they cannot see that the demonstrations of quantum entanglement have essentially disproven SR!

    FOLZONI

    PS: Should I surmise from the angry tone of your posting that "to learn who rules over you, simply find out whom you are not allowed to criticize" that the one I'm not allowed to criticize is Einstein?
     
  18. paddoboy Valued Senior Member

    Messages:
    27,534
    Criticise who you damn well like. Me too if that makes you feel good. You don't really get it do you?

    Please Register or Log in to view the hidden image!

    What fools say on a isolated forum like this, open to any Tom, Dick, and Harry, is affecting and impressing no one other than yourselves, and giving each crank some sort of warm inner glow, while the rest of the forum laughs and raises eyebrows....

    Please Register or Log in to view the hidden image!


    If your delusions of grandeur see you imaging that you are making any difference to scientific knowledge and discovery, then keep imaging dear chap. Far be it for me to disturb your dreams.

    Please Register or Log in to view the hidden image!

     
    danshawen likes this.
  19. FOLZONI Registered Senior Member

    Messages:
    129
    I see, paddoboy...
    ...so this is what qualifies on this forum as reasoned debate is it? - as well as reducing the forum to meaningless chatter.

    Hmmm! Interesting.

    FOLZONI
     
  20. paddoboy Valued Senior Member

    Messages:
    27,534
    Certainly reasonable debate and also fact. If you like folzoni, you could show me why you believe otherwise?
    Criticise who you damn well like. Me too if that makes you feel good. You don't really get it do you? What fools say on a isolated forum like this, open to any Tom, Dick, and Harry, is affecting and impressing no one other than yourselves, and giving each crank some sort of warm inner glow, while the rest of the forum laughs and raises eyebrows....
    If your delusions of grandeur see you imaging that you are making any difference to scientific knowledge and discovery, then keep imaging dear chap. Far be it for me to disturb your dreams.
    There is another forum though called "Cosmoquest"which have far more stringent rules with regards to cranks, pseudoscientists and your common variety nut.
    They are treated with far less tolerance over there.
     
    danshawen likes this.
  21. brucep Valued Senior Member

    Messages:
    4,098
    You can't debate any of the subjects you mention in your opening post. Clearly you're scientific illiterate on the the stuff you think is wrong. Your initial comments were to shock and to show me you're a clueless crank. Another entry into my ignore list. Pretty huge list.
     
    danshawen likes this.
  22. paddoboy Valued Senior Member

    Messages:
    27,534
    Bingo! That's what these nuts are attempting to do...similar to the "Shock and Awe" of the Iraq war.

    Please Register or Log in to view the hidden image!

    Like the proverbial cocky on the biscuit tin, they ain't in it. Science/cosmology proceeds without them, and its only forums such as this that there nonsensical crap are read, laughed at, and then totally forgotten.
     
    danshawen likes this.
  23. FOLZONI Registered Senior Member

    Messages:
    129
    Cocky on the biscuit tin!!!!??? So it must be true paddoboy - that you are from the University of New South Wales or some other bigot-Australian institution; NSW being a state where Einstein's BS is even taught in the last year of high school!
    Science today is crippled. Why? Because physics/cosmology in particular has gotten nowhere in the last 100 years specifically due to following Einsteinian prescriptions. Happily however this perverted Einsteinian reign is coming to an end - and you yourselves have already demonstrated that it's coming.

    Please Register or Log in to view the hidden image!



    How? Because quantum entanglement demonstrates faster-than-light (FTL) signalling - and it is now demonstrated every day all over the world in irrefutable experiments! And this FTL information transfer means ONLY one thing. Einstein's relativity - specifically SR - has been disproven and is now on the way out!

    Please Register or Log in to view the hidden image!



    So how do you

    Please Register or Log in to view the hidden image!

    Please Register or Log in to view the hidden image!

    know this? You know it from your three postings above. Rather than providing evidence for Einstein's teachings you resort entirely to ridicule & abuse - admittedly of a rather comic and crude kind (cocky on the Arnott's Biscuits tin

    Please Register or Log in to view the hidden image!

    ) which can only alert readers to the fact that you have nothing really substantial to say.

    So please, please - keep up the abuse. We're* just lovin' it!

    Please Register or Log in to view the hidden image!



    FOLZONI

    *By "we", I include danshawen!
     
    Last edited: Nov 28, 2015
    danshawen likes this.

Share This Page