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Ok, suppose Macro-entanglement is possible

  1. Feb 15, 2012 #1
    Suppose that Macro-entanglement is possible, how would one go about this entanglement?
    and a followup question, can particles that aren't the same type become entangled?
    Since all waves can be interpreted as particles and all particles can be interpreted as waves, can one entangle electromagnetic waves with particles? or is that idea redundant?
    and one last question, i cant find the answer anywhere, but what is h in the equation ΔxΔp≥h?
    if anyone can answer these questions, it would be nice
  2. jcsd
  3. Feb 15, 2012 #2


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    to quote from wikipedia (which, I know, is not the most reputable source)

    "Macro-level quantum entanglement has been proposed, but it is so far out of the realm of current physics that nobody believes it."

    Since it doesn't happen, you can propose any mechanism you wish. Any conclusion is true when you start with a false premise.
  4. Feb 15, 2012 #3
    Macro entanglement is indeed possible, through amplifying two entangled photons into a macro state (via unitary quantum cloner).
  5. Feb 15, 2012 #4
    since two particles are entangled when they interact in a way that makes sure that if one particle is one way, the other particle is certain to be a certain way corresponding to its partner, could you take that interaction and place it upon large objects?
    heres an example;
    bob and alice each have a ball. they throw the balls into a dark room in such a way that wherever one ball lands, the other ball is guaranteeing to be on the symmetrically opposite side of the room. now, the way the balls are thrown also creates quantum superposition, there is no way, even with extreme chaos theory calculating, to know where the balls landed.
    would that entangle the balls? or is it just a coincidental state in which the balls are in?
    it was a bad example, of course but there is still one part of my series of questions that wasnt answered;
    can a particle be entangled with a particle of a different type? can electromagnetic waves be entangled with particles?
  6. Feb 15, 2012 #5
    also, i suppose that Dual Particle-Type Entanglement is possible considering how quantum mechanics states entanglement. the last question is if electromagnetic waves can be entangled, i mean in a certain way of course

    all waves can be interpreted as particles, since any particles can be entangled, supposedly, one can theorize that the position of an electromagnetic wave-particle can be entangled with the position of photons, electrons, planets etc. etc.

    but that leaves another question, which once answered, many truths will be unfolded;
    HOW can one entangle positions of electromagnetic wave-particles with positions of other types of particles?
  7. Feb 15, 2012 #6


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    h is the Planck's constant, it is about 6.6*10^-34 in SI units (kgm^2/s).
  8. Feb 15, 2012 #7
    I should mention, everything is in principle entangled, either directly or indirectly.
  9. Feb 15, 2012 #8
    Doesn't liquid helium count as macro-entanglement? I mean there's a bunch of atoms that are so close together they become entangled, and you can visibly see the effects of that entanglement on the macroscopic level...
  10. Feb 16, 2012 #9


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    You must be talking about some metaphysical thing that has no basis in physics. In the sense in which the term entanglement is used in physics, "everything" is NOT entangled.
  11. Feb 16, 2012 #10
    You might want to dispute that with the physicists who wrote Quantum Enigma. Also Jonathan Allday discusses entanglement as an interaction with the measuring device and the quantum system. I dare say you're questioning the use of the word entanglement in that case too.
  12. Feb 16, 2012 #11
    I am going to choose to answer a part of one of your questions, I hope it helps. You could, in theory (as in I don't know if the experiment has been done), entangle a photon and a particle that possesses charge, such as an electron or atom. First, generate two entangled photons through a nonlinear process such spontaneous parametric down conversion (SPDC). These photons can be entangled in several different degrees of freedom, depending on the experiment. For simplicity, say the photons are entangled in energy (or frequency, same thing) and go in different paths. That means if you do a measurement and find the photon that went left has energy e1 the other one that went right has energy e2. You could then place an atom in the left path. This atom should be able to absorb a photon of energy e1 that will leave it in state a1, or absorb a photon of energy e2 that will leave it in a state a2. Now the photon on the right is entangled with the atom in the left path. The state of the combined system will look like this in dirac notation: |e1,a2>+|e2,a1>, which is an entangled state.
  13. Feb 16, 2012 #12
    which that brings something to mind, that is that you can trade entanglements between particles. its an interesting concept,it is easy to entangle two photons, and almost as easy to entangle a photon with say an electron, that electron can be entangled with an atom, that atom entangles with another atom, so on and so forth. in practice it would be nearly impossible to trade entanglements in such a sequence that can entangle large objects, but it would be easier than direct entanglement. but what you stated is kinda a different concept, the two could easily be used together though to achieve macro-entanglement of large objects. thanks for the information
  14. Feb 16, 2012 #13
    I still don't get why liquid helium wasn't mentioned because that's entanglement on the macroscopic level, it's just that the atoms continue to keep forming entangled systems after they have been measured in some way because they are so close together.

    Particles don't get entangled unless they share the same quantum state, and not every atoms is doing that. There's no other definitions for quantum entanglement.
  15. Feb 17, 2012 #14
    First of all, there is much to dispute with Quantum Enigma, which presents the issues of entanglement, counterfactual definiteness, and many other topics in an incredibly misleading light. (If you want a popular book of that type Quantum Reality by Nick Herbert might be a better choice; many of the ideas in Quantum Enigma were in fact taken from Herbert's book.) Furthermore, as I told you in another thread not every interaction is an entanglement. Entanglement occurs only in the situation when the quantum states of two different particles become inseperable from one another, in the sense that you cannot decompose the two-particle state into a product of one-particle states. It is quite possible in quantum mechanics for two particles to interact for a short time and then lose all connection with each other. Entanglement is an allowed feature of quantum interaction, not a required one. So it's a very bold thing to say that all the particles in the universe are entangled. There are people who do believe that, like some superdeterminists (look up superdeterminism in the context of Bell's theorem), but it's relatively rare.

    As to whether the measurement device becomes entangled with the particle under observation, or whether it collapses the wave function of the particle under observation, that's an interpretational question in which there can and will be reasonable disagreement.
  16. Feb 17, 2012 #15
    You can always consider any system of two particles, regardless of whether they're entangled or even interacting, to be described with a single quantum state. The key characteristic of entanglement is that the quantum state of the two-particle system cannot be decomposed into a product of quantum states for each particle. In contrast, particles with ordinary interactions have a combined quantum state which can be decomposed in this way.
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