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Quantum Teleportation

  1. Feb 20, 2006 #1
    Will quantum teleportation be the future transportation mode for humans?
     
  2. jcsd
  3. Feb 20, 2006 #2
    touqra

    At present, quantum teleportation has been used to transfer information about the state a physical system, e.g. the polarization of a photon or the excitation of an atom. But that is different from teleporting the actual photon or atom, and (as far as I know) there is not a way to perform that latter type of teleportation.

    I have heard arguments that in principle the state of a person could be teleported. But practical constraints, such as the complexiety of the system, would seem to prohibit this example of quantum teleportation from being realized.

    Please follow up if this is unclear.
     
  4. Feb 20, 2006 #3

    ZapperZ

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    This is why I cringe when those people in that field of study started using the phrase "quantum teleportation". This is a perfect example where, if someone didn't know what that means, they'll confuse it with the Star Trek teleportation.

    Those two are not the same. They are not even cousins.

    Zz.
     
  5. Feb 20, 2006 #4
    mmmm

    eerr, since when?! transfer of *information* instantaneously?so information *can* travel from A to B faster than light in a vacuum?...
     
  6. Feb 20, 2006 #5

    Physics Monkey

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    Don't worry alfred, information still can't go faster than light. In order for the person on the other end to recover the state there always has to be classical communication.
     
  7. Feb 20, 2006 #6
    alfredblase:

    yeah what physics monkey said...not instantaneous, not even faster than light, instead requiring one classical and one quantum communication channel.

    p.s. I know some groups (Gisin, Geneva) have tried to measure a "speed" for information transfer via a quantum channel, i.e. entanglement, but as far as I know they have not measured one yet.
     
  8. Feb 20, 2006 #7
    Transfering the state of a physical system...does it mean I will have duplicate another photon in another place? If the photon is a human, then, I've actually cloned him in the physics way?

    Practical constraints? But how about quantum computers? Sending bits and bits of information can be complicated too.
     
  9. Feb 20, 2006 #8

    ZapperZ

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    Maybe it might be a good idea, before you ask the original question, for you to first discover the definition of "quantum teleportation". It might surprise you to learn that what we have here is a transfer of INFORMATION, not the transfer of the object carrying that information. That is what transfer of a "state" means.

    Zz.
     
  10. Feb 21, 2006 #9
    This knowledge may someday help in transferring one person from a place to other, but this operation will require several orders of magnitude more processing capabilities than the used nowadays in laboratories.

    In fact the term quantum teleportation (QT) does not imply flux of matter through space.

    A TV program where a lady teaches you how to prepare a cake may have something in common with QT. The basic and most fundamental difference between these two processes is that, in QT the lady intends to teach you how to construct a system in a given state which she cannot investigate in principle, otherwise the information about the actual state of her cake will disappear. She teaches you to faithfully construct an exact copy of something that is with her, but she also does not know details about it.

    Best Regards

    DaTario
     
  11. Feb 21, 2006 #10
    touqra, great follow up question.

    like ZapperZ said, it is information about the photon that is transferred but not the photon itself. Photons have two orthogonal (perpendicular) polarizations, called H and V for horizontal and vertical. Quantum mechanics allows for superpositions of these polarizations, such as H + V, which is a "state" of the photon. Quantum teleportation transfers the state of one photon to another photon, even when those two photons are spatially separated. But the second photon has to exist before teleportation can happen!

    So, like in DaTario's analogy, someone giving you information to make something is very different from them giving you that thing. Another example might be a fax machine. When someone faxes (teleports) to you a document they do not send the original, only the information on it. You must already have some paper to print this information on. (In truth, teleportation is slightly more complicated than this.)

    Finally, in quantum teleportation the original information is always destroyed. Not the photon, but the state it was in changes. Instead, only the second photon contains the “state.” But this is not a surprise (well, technically not a surprise) because there is a no-cloning theorem in quantum mechanics. Search the forum for more information on that.

    So you couldn’t clone humans this way.

    But could you teleport a human? Well, could you fax a human?

    Great questions...
     
  12. Feb 4, 2011 #11
    hi
    no information can't travel with speed than light.because in teleportation protocol Alice send results of her measurement to bob via classical channel. so special relativity is not violated.
    also no-cloning theorem is not violated because after measurement Alice's qubit is destroyed.
     
  13. Apr 23, 2011 #12
    okay, the answer is highly unlikely.
    I tried to be very basic another thread as the individual didn't want to know all the ins and outs but just wanted basic idea what quantum entanglement meant and how it related to teleportation. Some people ZapperZ think that if they make it complicated that they must be and are showing they are superior when in fact this is not necessarily the case. Any way, to attempt to remove the complication: The quantum teleportation has more to do with the idea of knowing the state (of all possible states) of a particular particle that is one halve of an entangled pair. Each halve being opposite the other being a "known", so once you observe the state on one particle you know the other is the exact opposite. No physical disappear from here and reappear over there actually happens, you already have both particles. Okay, how do you get entangled pairs? The answer is, in several ways, for instance when you have calcium atoms energized and they become de-energized they produce an entangled pair of photons each with the opposite state maybe the first has a CW spin or maybe a CCW spin, you don't know till you look. You change the state of the first one by looking and observing it is CCW and you know automatically the other is spinning CW. We can go down the rabbit hole but now you know generally there is no poof it was here now poof it is there (Uh, please, I wrote that last sentence and laughed. Before you respond with a blah blah blah about virtual particles poofing into existance etc. remember, that is not what he wanted to know)
     
  14. Apr 23, 2011 #13

    ZapperZ

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    You are responding to the question that was posted in 2006! The ship has left the harbor a long time ago.

    Zz.
     
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