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Entangled Particles Allow for absolutely crazy things?

  1. Oct 26, 2003 #1
    "Entangled Particles" Allow for absolutely crazy things?

    I was reading a little bit about entangled particles... I cant be sure how much of it I grasped, but as I understand it for every particle in the universe spinning in direction X, there is another particle spinning in the exact opposite direction. When you change the spin of one the spin of the other changes as well.. has something to do with Schroedigner's box if I remember.

    Anyhow... this got me to thinking. The monitor I'm staring at for instance, is made up of particles. If the exact (opposite) corresponding group of particles in the universe were acted upon in an identicle way... my monitor could say - fly across the room? This seems absolutely crazy to me, but at the same time it seems like the theory allows for it?

    If such a thing could be possible, it doesnt make sense to me how the universe can maintain any sort of stability, with particles flying all over the place and interacting, it would seem that everything would be getting ripped apart. Someone help! :)
  2. jcsd
  3. Oct 26, 2003 #2


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    No, not "every" particle. Entangled particles have to be prepared, either by technology or by nature. The evidence of the people doing entanglement experiments is that making entangled particles isn't easy. Most of the experiments are done with photons, rather than the neater case of electrons, because of the difficaulty.
  4. Oct 26, 2003 #3
    Re: "Entangled Particles" Allow for absolutely crazy things?

    How are you going to make an entangled particle move somewhere? You can measure its spin, but that isn't going to make anything get up and fly anywhere. Besides, we can't completely control the quantum properties of particles: if you measure their spins, you can get a spin up or a spin down, but you can't ensure you'll get one or the other, even for one particle, let alone a whole collection of them.
  5. Oct 26, 2003 #4


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    As selfAdjoint says, the particles have to be carefully prepared. The two-particle system is in a superposition of states; each particle can be either spin-up or spin-down, and the other has to be the opposite (conservation of angular momentum).

    When the two particles interact, they become part of a "closed" quantum system, in which a superposition of states exists. As soon as either of the pair interacts with anything, the system is no longer closed, and the particle has to "choose" whether it should be spin-up or spin-down. The actual value that you'll get it random. What is NOT random is that the other particle's wavefunction is collapsed "at the same time," relativistic effects notwithstanding. The other particle chooses what it should be, based on what the measured particle "chose" to be. Before the measurement, neither of the two particles has a defined spin; after measurement of just one, both have defined spins.

    This is the "spooky action-at-a-distance." But fear not -- it can't be used to transmit energy, information or anything else that would violate relativity. It also has nothing to do with making particles in your monitor move.

    - Warren
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