FTL communication using quantum entanglement

Discussion in 'Highly Technical' started by slashbinslashbash, Aug 28, 2012.

  1. slashbinslashbash

    slashbinslashbash Golden Member

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    Ok. Typical scenario. You have 2 entangled particles, let's say A and A'. You observe/determine the spin state of A, that means the spin state of A' is now determined, instantly. This is something that is already being observed experimentally; don't ask me how, or what kind of detectors are involved, or how the particles are kept isolated from their surroundings during their initial travel/separation time; I don't know. Books that I have read suggest that this is not really communication because you can't know one way or the other how they will turn out; only that they will turn out oppositely. So if A is up, then A' is down; and if A is down, then A' is up; but you can't know in advance whether A will end up up or down. Fine.

    However, I view the very state change at a given moment as effective communication, especially when multiple entangled pairs are used. Say we now have pairs A and A', and B and B'. Observe/determine state of A and then B => state of A' and then B' becomes determined. Or vice-versa. So a very simple "yes" or "no" can already be communicated: A then B = yes, B then A = no.

    But now what if you have arbitrary numbers of entangled pairs? You can communicate arbitrary amounts of data.

    Even better, you don't have to have arbitrary numbers; you can get by with just 2 entangled pairs. Let's assume that our spin-change detector has a time-resolution of 1 second. So A, (1 second), B = 1. A, (2 seconds), B = 2. And so on. You can do this to encode any number, and as we know from information theory, every number represents a unique communication/idea/datum. Any computer program ever written can be represented by a single number. Of course, if the time-resolution is 1 second, we will be waiting a long time for those longer messages. But what if the time-resolution is much greater? Say, a microsecond (which I believe we're already capable of, given that we're running tests showing that this stuff is happening faster than the speed of light, and the timing has to be very precise for stuff like that)? Then we've got communications going at over 100 kBps, if my back-of-the-napkin math is correct. Assuming efficient coding and a limited, pre-determined vocabulary, a lot of ideas could be communicated in a second or two -- over arbitrary distances.

    Am I missing something here? Everything that I've read pooh-poohs the idea of FTL communication via quantum entanglement/non-locality based on an argument that only discusses a single pair of entangled particles.
     
  2. Paul98

    Paul98 Diamond Member

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    No, there is no way to get information sent through this. The entangled particles give random results. Lets say I have a set of particles that I entangle, I keep half and send you half. So now we both have 1 of a pair of the entangled particles. I then look at the state of the particles which means you get the opposite state. We both get a random group of states, it's just that we get a set of opposite states. So after you check yours or I check mine I know the results you will get since they will be opposite from mine.

    It's like I take a red and blue ball, they are randomly put into a sack so we don't know who has which. We then travel away from each other. I pull mine out, I then instantly know which you have. Plus same for when you pull yours out.
     
  3. slashbinslashbash

    slashbinslashbash Golden Member

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    But it's not as simple as that. Both balls exist in a state of not-red, not-blue, both-red-and-blue until one of us observes it. At that instant, the other one will know that the determination has happened. It's not just knowing that yours must be red if mine is blue. It's seeing that mine has become blue, so yours must have been observed to be red.

    Somehow, scientists are experimentally judging *when* these changes take place, down to very small intervals of time. (So that they can time it vs. the speed of light and see that it happens faster than light can travel between the two points.) It's like, when you pull your ball out and see that it's blue, my bag instantly disappears and I can see the red ball that was inside of it. So I know *when* you make your observation; I can detect the change somehow. Again, I don't know exactly how this is done, but it must be done somehow in order for any of these experiments to work.

    And that is the important point; I don't care whether it's red or blue, just that you have made the determination, one way or the other.
     
  4. wuliheron

    wuliheron Diamond Member

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    Some physicists held out hope that entanglement could be explained by faster than light travel and was more fundamental than Indeterminacy, but experiments have shown the opposite. Like everything else in quantum mechanics it turns out entanglement is also subject to indeterminacy. It also turns out entanglement is contextual, that is, the strength of the entanglement varies with the number of particles entangled.

    http://physicsworld.com/cws/article/news/2011/mar/24/quantum-probe-beats-heisenberg-limit
    http://www.sciencedaily.com/releases/2009/07/090722142824.htm

    So unless you can show exactly how quanta are contextual and how indeterminacy applies it's all guesswork.
     
  5. Paul98

    Paul98 Diamond Member

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    it's an analogy to help you understand why you can not send information the way you want to. It's simple if one person sees that theirs is red or blue they know that the other person will see theirs as the opposite. You can't send any information this way.

    No, this is where you are going wrong, the "bag" doesn't disappear, and you still can't see the ball. You have no way of knowing if the other person has made the measurement or not. Both people still need to make the measurement aka open the bag and see what ball is inside. You have no way of knowing if I have made a measurement or not, you can't see the state of the ball till you measure it. Once you measure it you will know you got the opposite results of what I got.

    Lets say I have 10 particles I entangle pairs of them. I then send you half I keep the other half. I then want to send a message, I try and send you a binary message where I measure the particles where I want you to get a "1" and don't measure the ones I want to be a "0". The only way for you to get the message is to measure the particles, so you measure all of them which gives you random states. You have no way of knowing which the other person had already measured or not.
     
  6. Agent11

    Agent11 Diamond Member

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    Thats the problem. If they could tell if one was measured you would only need to send one. Then the states would be measured/unmeasured 1/0.

    A lot of quantum mechanics seems weird and totally useless for practical applications.
     
    #6 Agent11, Aug 29, 2012
    Last edited: Aug 29, 2012
  7. Modelworks

    Modelworks Lifer

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    Quantum entanglement experiments for communication have already been done and shown to work the problem is taking it to the next step where it could be used as a practical way of communicating without requiring millions of dollars of lab equipment.
     
  8. Modelworks

    Modelworks Lifer

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    There seems to be a lot of confusion about measuring quantum states. It is not as absolute as you can't do anything with the particles or they vanish. It is more like you can hear the person in another room, even though you don't see them visually. With a lot of very expensive equipment it is possible to create quantum particles that have a predetermined state . Some physicist were concerned that after creation the particles might be free to change state meaning random states would be the result, but on doing further experiments it was found that the particles do preserve their state and don't just randomly change. It all comes down to the creation process and when done correctly you can end up up with entangled pairs or even 3 or 4 particles where one is known without measuring any of the particles. Right now though it is a VERY expensive process the equivalent of the cost for sending 1 bit of information would be over $100 million.
     
  9. videogames101

    videogames101 Diamond Member

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    You're gonna need a link buddy.
     
  10. Modelworks

    Modelworks Lifer

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    Nope, I don't need a link. Ask physicist at any decent university , the experiments took place last year and were talked about quite a bit, there may be online articles about it, but that isn't where I learned about it, so I don't know.



    quick search only turned up the original paper from early last year that has a lot of the details but not the experiment itself, that was done I think in November of last year.
    http://arxiv.org/abs/1101.2565
     
    #10 Modelworks, Aug 29, 2012
    Last edited: Aug 29, 2012
  11. DrPizza

    DrPizza Administrator Elite Member Goat Whisperer
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    I think you DO need a link. Extraordinary claims require extraordinary evidence. I just shot over to scholar.google and searched for all articles with "faster than light communication" and "entanglement," narrowed down to papers written after 2011. I skimmed through the first 10; each implied that faster than light communication was not possible.
     
  12. Mark R

    Mark R Diamond Member

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    While communication using quantum entanglement is possible, and indeed, well demonstrated for special purposes, such as cryptographic key exchange (you can actually buy such devices off-the-shelf as commercial products), the problem is that the communication is not faster than light.

    Most theoretical physicists believe that FTL communication is not possible via this route - though I can't explain their reasoning, as it's way beyond my understanding.
     
  13. Paul98

    Paul98 Diamond Member

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    If entanglement could send information ftl it would cause huge problem with the relativity of simultaneity.
     
  14. queequeg99

    queequeg99 Senior member

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    Given the existential headache the relativity of simultaneity caused me, I'm not sure if creating problems with it would be such a bad thing. I might be able to more easily convince myself that I have free will.
     
  15. pandemonium

    pandemonium Golden Member

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    I also remember reading about this, so I went looking and found a few experiments that note FTL entanglement being diagnosed:

    August 2008
    Physicists at the University of Geneva achieved the weird result by creating a pair of ‘entangled’ photons, separating them, then sending them down a fibre optic cable to the Swiss villages of Satigny and Jussy, some 18 kilometres apart.
    April 2011
    To teleport light, researchers led by Noriyuki Lee of the University of Tokyo had to destroy it in one place, and re-create it in another. (Additional information also reported on Space.com.)
    [Additionally, Science magazine has their contents viewable online if you're an AAAS member.]
     
  16. William Gaatjes

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    Here is what i find interesting :
    This is all a bit of far fetched assuming but still interesting to wonder about.
    We know that light (photons) needs to travel from the Sun to the Earth ideally with the speed of light in vacuum = c. Because of the distance, light takes about 8 minutes to travel.
    The big question is if magnetic monopoles can exist.

    Here is the idea :
    Every 8 minutes, there is a magnetic reconnection between the magnetic field of the Earth and the magnetic field of the Sun. Assuming the magnetic field as discrete "lines" or packages, there is the coincidence that this also takes about 8 minutes.
    Now, the whole quantum entanglement and all the measurements is all about spin.
    From recent research, it is discovered that the electron can be seen as two and even three distinct quasi particles : One determining the magnetic qualities, the spin : the spinon.
    And one determining the electric qualities : the orbital or "position" (although the electron seems to be everywhere at once, (depending on the orbit and energy)) the holon.
    Now there is also an orbiton that carries the angular momentum.
    http://arstechnica.com/science/2012/04/electrons-like-gaul-come-in-three-parts/
    When looking all again as 3D fields, it still makes sense except for the orbiton.
    Assuming spherical 3D waves :
    This to me seems more of an intersection between a magnetic wave and an electric wave.
    I am wondering off again. Let's assume that the spin of any particle is because of the characteristics of the magnetic field lines or just field, forced to a maximum of c.
    My question is, is there ever done an experiment with entanglement using the electric charge ?
    I am wondering if even the slightest disturbance in a magnetic field would cause such a dragging effect that in our universe, the speed of any particle or quasi particle is limited to c as maximum.
    How to avoid any magnetic disturbance ?

    Please come "wonder" with me :

    Henry Saiz feat. Anneke van Giersbergen - Come Wander With Me
    http://www.youtube.com/watch?v=dXC0WGduHYg
     
    #16 William Gaatjes, Sep 15, 2012
    Last edited: Sep 15, 2012
  17. William Gaatjes

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    I do not know why, but for some reason, i think the dipole is key or better yet, the cause of the limitation.
    We will find out in the future when NASA has done more research about the finer details of the magnetic reconnection in space between the entangled magnetic fields of the Sun and the Earth.
    I am sure more information about monopoles will also arise. Creating a more detailed picture.
     
  18. martixy

    martixy Member

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    And the logical first question is...
    How do you force it to collapse to a state of YOUR choosing?
     
  19. wuliheron

    wuliheron Diamond Member

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    You lie down in bed, close your eyes, and repeat, "I think I fly, I think I can fly...." until it happens.
     
  20. rollins

    rollins Junior Member

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    I'm really trying to get my head around basic concepts of quantum mechanics but reading explanations like this makes me think that QM is a load of hocus-pocus.

    So what I understand is that if two particles interact and are separated, even by millions of light years then you can determine the up or down spin of one particle by measuring the other.

    But going to Paul's red and blue ball analogy... So say we actually did this, there was a blue and red ball. I close my eyes and put each ball in a sack and seal it. Paul then flys off to the other side of the universe and later I pull a blue ball out and determine that Paul had the red ball.

    Seriously... this is science? Paul had the red ball all along and it's just we kept that fact hidden until much later. I don't see the science in that.

    It's just that it sounds to me like the QE thing involving particles is the same. A scientist may determine that particle A is down-spin and therefore particle A' is in upspin but my thought is that A' was in upspin all along and the scientist who did the measurement didn't affect the other particle.

    So surely there's more to it than this. I'd appreciate if anyone could point out what I'm not understanding.
     
  21. Paul98

    Paul98 Diamond Member

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    Look up Bell's Theorem, or there are a good number of video's on quantum physics such as http://video.pbs.org/video/2167398185
     
  22. irishScott

    irishScott Lifer

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    Alright, I have zero knowledge of the subject, but if that analogy is accurate, couldn't it still theoretically work for communication?

    The problem as I see it is the lack of knowledge of whether the other person had observed the particles or not. Fine. Create a synchronized system where each side only observes the particles at a given time.

    Even if FTL communication isn't possible, imagine the importance of, say, a perfectly secure and instantaneous phone or other communication device. It would effectively render the internet obsolete. Granted all the technology required to back such a system is likely centuries out, but still...
     
  23. Paul98

    Paul98 Diamond Member

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    No, it doesn't matter if you know what is being observed or not, when you observe your particles you will still just get a bunch of random results. If they are entangled or not when you look at your results they will be random.

    and if FTL communication isn't possible then clearly you can't have instantaneous phone or other communication devices. I do not think FTL communication will ever be possible in any normal way you would think about it.
     
  24. SMOGZINN

    SMOGZINN Diamond Member

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    The way I understand it you can send a message FTL with this method, it is just that no one can receive that message, it gets re-randomized as soon as anyone tries to read it.
     
  25. Paul98

    Paul98 Diamond Member

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    How would you send a message in the first place? It doesn't get re-randomized as you can tell when you compare the measurement results.

    Lets say you have a bunch of particles entangled, I can measure or not measure them. If I measure I get an up or down measurement, I can't control which I get. For each that I measure I know that the other person if they measure it's entangled particle will get the opposite of what I measured. When one person looks at their measurements they just get a bunch of random up/down measurements. It doesn't matter if the other person measured theirs or not. When you compare the measurements if they measured entangled particles one will get up the other will get down. But they can't control which they get.