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Quantum Entanglement - Two Places at Once

  1. Jul 24, 2011 #1
    Question: If two particles are entangled, and instead of "measuring" one, you were to take apply a physical force to it, would the other particle experience the same physical force.

    Simple minded analogy (for my purposes): If on a billiard table two ball are entangled, and you hit one with a cue ball, does the other entangled ball move in the same direction as if it were struck with that same cue ball?
  2. jcsd
  3. Jul 24, 2011 #2
    No, that would imply it would be possible to create an FTL comm device

    You seem to have become victim of mainstream scientific TV programs, which popularize an entirely bogus concept of entanglement that has nothing to do with its reality
  4. Jul 24, 2011 #3
    No. I don't believe I am the victim of anything other than a lack of knowledge about the subject matter, thus the reason for the question.

    As Dr. Chinese mentioned in his previous posts...I am asking from a perspective of step 1. Once I understand step 1, then would be the time to move on and consider relevant devices that could be constructed based upon a good understanding of step 1.

    Thank you for your reply afstgl.
  5. Jul 24, 2011 #4
    I've said that because I myself watched a lot of stuff on QM and especially entanglement, where supposed scientists claim exactly what you asked, along with actual matter teleportation, FTL communications and so on.

    The only thing that happens between entangled particles is measuring the state of the one immediately defines the state of the other, it is not like if you jerk one particle around, the second will follow immediately :)
  6. Jul 24, 2011 #5


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    Good point, I always like it when you start at step 1!! And welcome to PhysicsForums!

    Step I: The EPR argument was that an entangled particles were in a state such that Alice + Bob was a known quantity; therefore observing Alice yielded the value for Bob. Since there are multiple properties for Alice & Bob, you could measure Bob for some other property and get the values for Alice and Bob for 2 non-commuting properties. Quantum Mechanics does not support that idea, ergo QM must be incomplete. But they did NOT dispute that the predictions of QM would be correct, just that they didn't go far enough. For all anyone knew, there might be a more complete theory at a later date. Certainly, a reasonable idea.

    Further, if QM was complete they presumed there must be some kind of instantaneous (spooky) action at a distance. You can imagine what Einstein thought of that idea! They dismissed the idea that non-commuting observables were not sharply defined (which is the non-realistic viewpoint) as unreasonable.

    Keep in mind that no one knows what the actual underlying mechanism really is. So that is Step I, and obviously in Step II we learn why that is wrong. I.e. that the EPR argument that QM is accurate but incomplete is actually flat wrong.
  7. Jul 26, 2011 #6
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  8. Jul 26, 2011 #7
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  9. Jul 26, 2011 #8
    Dr. Chinese...this goes in a slightly different direction than entangled particles...but...attempts to address virtual particle creation and its source of energy for creation as potentially from black holes. Just throwing out an idea for Step 1.

    I had proposed in another post (I'll have to dig it up) that I would like to attempt to use two opposing magnets of sufficient strength to separate virtual particles as they form, and thus, keep them from annihilating each other...until the particles could be re-routed to a location of my choice and then reunited for their annihilation. By doing this, I would hope to utilize this scenario to generate a thrust on one side of a ship, due to more annihilations of virtual particles occuring on one side of the ship versus the opposing side.

    One of the replies seemed to imply there would be a necessity for a large amount of energy to create matter from nothing...which I understand...but...this argument appears to be two sides of the same coin. For the virtual particles to appear in the first place, wouldn't there necessarily need to be a large amount of energy causing these particles to appear in the first place? I understand the comment is virtual particles can exist "temporarily" without violating physics laws...

    I had proposed that a possible source for the energy that would cause the rather active appearance of virtual particles, could possibly be from the stretching of space by the black hole, allowing energy to flow into a sub-space, similar to a bowling ball on a trampoline allowng water to flow through the fabric when its stretched.

    The bowling ball would allow a material such as water to pass through the holes between the strings of thread. In a similar manner, a black hole would stretch space such that the graininess described at the quantum level would be made more porous, or the holes between strings would be enlarged to allow matter and energy to move out of the space we are familiar with, and into a "sub-space". If the volume is confined in the "sub-space" then there might be a "pressure" that would cause the energy to try to leak back into our universe, and this is the source of the energy for virtual particle creation. (The sub-space would not necessarily need to be confined) This could be a partial source for some of the matter missing from the Universe, it has gone into the black holes...or if the weight of the virtual particles being created and annhilating each other is included, in the mass calculation, I would suppose that would be a large mass if the description of virtual particle creation rates is to be believed as "seething" at the quantum level. Possibly a way to test this would be to assume that the rate of creation of virtual particles is not constant all over the Universe. In fact, it would increase as a person approaches a black hole, and falls off as one gets further away from a black hole. A way to test this would be to send a probe away from the center of the galaxy, and a probe sent toward the center of the galaxy. If there is a fall off in virtul particle creation rates for the probe leaving the galaxy and an increase for the probe getting closer to the galactic center, that might prove the rate of creation for virtual particles is possibly linked to the black hole opening holes in our space as described above...

    Potentially, over time, the rate of creation of virtual particles might increase if the quantum barrier is unable to prevent the energy leaking into our universe. i.e. as the universe ages, more matter and energy is pulled through the black holes into a sub-space, and eventually the energy is high enough to penetrate the quantum barrier across the entirety of the universe resultiing not in a big bang, but in a huge flash of radiation, where the new universe will begin to coelasce galaxies and do this whole scenario again.

    If you've read this far, I realize you've probably branded me as a tin foil hat wearer...if not I'd like to see your comments on what I've written above.

    I think I posted this in a different form under "Beyond the Standard Model" of this forum.

  10. Aug 4, 2011 #9
    Any comments on what I've proposed for the source of energy that creates virtual particles in the first place?
  11. Aug 5, 2011 #10
    No, local deterministic operations - operations in one part - don't affect the state of the other part. Only the probabilistic act of measurement can affect the second particle state (description).

    The force you are saying would be translated as a local quantum evolution - represented as a local unitary transformation (trace-preserving deterministic operation). And this kind of transformations do nothing to the quantum state in the other side.
  12. Aug 5, 2011 #11
    Thanks MrDemantao!

    Appreciate you taking the time to respond.
  13. Aug 5, 2011 #12
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  14. Aug 8, 2011 #13
    Qm is complete, in a sense, but also incomplete as a description of the underlying physical reality. One only has to look at the standard qm treatments of entanglement to see this.

    But of course that doesn't mean that a viable LHV description of entanglement of the sort that Einstein advocated (and that Bell mathematically formulated) is possible, since Bell showed, definitively, that it isn't possible.

    My understanding of the EPR argument is that it said the either 1) standard qm is an incomplete description of physical reality, or 2) there is spooky action at a distance in nature. They opted for 1) which I would guess is the way most physicists regard standard qm.

    Bell showed that an explicitly realistic and explicitly local hidden variable (LRHV) model of quantum entanglement is incompatible with the standard qm formulation. Subsequent experiments showed that LRHV models of quantum entanglement are incompatible with experimental results.

    It has never been shown that local hidden variables are not in nature. In fact, individual detection preparations are quite amenable to LRHV models. The problem is with formulating LRHV models of joint (entanglement) preparations where (presumed) global hidden parameters (relationships between entangled entities) are (presumably) determining nonlinear correlations between a global measurement parameter and the rate of coincidental detection, and where these correlations are not determined by the local hidden variables that determine individual detections, but rather by nonvarying relationships (per preparation) between the entangled hidden variables.

    LRHV models of quantum entanglement akin to Bell's formulation (and Bell's LRHV formulation seems to be pretty general) are definitively ruled out because they require that LRHV's model quantum entanglement in terms of (ie., that the entanglement correlations be determined by) the local hidden variables that determine individual detection. Thus, it can't be inferred from the violation of inequalities based on Bell's LRHV formulation that nature is nonlocal or that local hidden variables don't exist. Just that even if the relationships between entangled entities are produced solely via local interactions (ie., even if nature is exclusively local and hidden variables exist), then LRHV models of quantum entanglement are still ruled out -- a sort of Catch-22 situation for would be LRHV theorists.

    Wrt the OP my answer would be that it's unknown whether applying a physical force (such as filtration or detection) to one entangled disturbance would affect the other entangled disturbance. There's no way to ascertain this experimentally. But since there's a simpler (less exotic) explanation for entanglement correlations, then there's no reason to assume that that's what's happening.

    Having said that, I'm not sure that I understand your Step I and Step II. And, as always, clarifications/corrections on anything I've written here are appreciated.
  15. Aug 8, 2011 #14
    That's not it at all, since some theories claim everything is entangled, you would be controlled by some voodoo doll living On the opposite side of the universe. Quantum entanglement is a slightly more difficult concept than superposition, which if you're interested, you should learn about first. I won't explain it here because there are numerous posts around the site that will explain it better than I will. Entanglement simplified so much that it can barely be called entanglement anymore, consists of 2 particles that will always have the opposite value Than the other, if particle one has a positive charge, Particle two has a negative charge.
  16. Aug 9, 2011 #15
    Um, what are you saying? There might be local hidden variables, but they can't be local "realistic" hidden variables? What are they then, unrealistic hidden variables?
  17. Aug 9, 2011 #16
    We can infer from the amenability of individual detetection to LRHV formulation that local hidden variables exist. They don't cease to exist just because we decide to look at the joint context. Joint detection is determined by a different underlying parameter (a relationship) than individual detection. The assumption that the relationship is produced locally is just as valid as the assumption that it was produced nonlocally. We have no way of knowing how the relationship was produced. The only thing that's known from inequality violation is that the LRHV formulation that's the basis of the inequality isn't a viable model of quantum entanglement.
    Last edited: Aug 9, 2011
  18. Aug 9, 2011 #17
    OK, I think I now recognize your position. You're saying that, instead of or in addition to local hidden variables responsible for individual detection outcomes, there might be another class of local hidden variables responsible for correlations between multiple detection outcomes. I thought such a theory required an unlikely "preestablished harmony" between the second type of LHVs and the details of measurements?
  19. Aug 10, 2011 #18
    Not exactly. The idea is that the hidden parameter responsible for joint detection rate is a global parameter which isn't varying from pair to pair. It's just that LRHV models are required to explicitly describe the joint detection rate as being determined by the same hidden variables that determine the individual detection rate. I don't see how that's possible if the global hidden parameter that's determining joint detection isn't varying from entangled pair to entangled pair -- and apparently it isn't, because changing the global measurement parameter predictably changes the variable joint detection rate.

    We can assume that this unchanging global hidden parameter is the relationship between the entangled property of the entangled entities, and that random variations in the value of the entangled property determine the nonvarying individual detection rate.

    The hidden variable (the entangled property) that determines individual detection rate at each end can be assumed, without contradicting either standard qm or experimental results, to have a local cause. And it follows that if the entangled property has a local cause, then the relationship between the spatially separated entities carrying the entangled property has a local cause.

    This has supposedly been ruled out. However, this is based on the unreasonable requirement that LRHV models of entanglement be fashioned explicitly in terms of the hidden variable which determines individual detection.

    Considering that, then what we're left with is the ruling out of any model of entanglement based on that LRHV requirement.

    And whether there are ftl transmissions or action at a distance in nature, or nature is evolving exclusively in accordance with the principle of local causality with transmissions limited by c, remains an open question.

    So, while the answer to the OP question is, wrt some conceivable setups, demonstrably no, wrt Bell tests it's impossible to tell, afaik, if what's happening to the disturbance at one end is affecting the disturbance at the other end via some unknown ftl or spooky action at a distance mechanism.

    The Catch-22 for local realists is due to the idea that while entanglement is more or less understandable via locally produced relationship, it can't be viably modelled in terms of the conventional LRHV requirements.

    If the underlying global parameter determining joint detection is a relationship that isn't varying from pair to pair, then there's no need for any "preestablished harmony" in order for joint detection rates to vary, in the predictable and particularly nonlinear way that they do, as the global measurement parameter varies. For example, in the case of optical tests where you're dealing with pairs of polarization entangled photons you would expect the joint detection rate, which is a measurement of intensity, to vary as it's observed to vary as a nonlinear function of the angular difference between the polarizer settings.
    Last edited: Aug 10, 2011
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