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First quantum teleportation of macroscopic objects

  1. Nov 18, 2012 #1

    Does anyone know how big that ensemble of rubidium atoms is?

    Let me make sure I understand quantum teleportation correctly, I probably don't. Some scientists entangle two rubidium atoms. Then they separate them at a speed less than the speed of light, in this case 150 metres away. They then change one set of the rubidium atoms and the other set 150 metres away changes instantaneously? Am I right? More details would help.
  2. jcsd
  3. Nov 18, 2012 #2

    Jano L.

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    I do not understand this either, but if it worked as you describe above, it would be astonishing. It is probably something more complex and less spectacular.
  4. Nov 18, 2012 #3
    First of all there is nothing really getting teleported. The media prints a news headline "photon gets teleported" this is actually not accurate at all. When a photon hits an 'entangled' atom its energy state goes up and that photon is annihilated . When the atom gets rid of the excess energy and goes back to its original stated it shoots out a new photo(photoelectric effect). So the entangled atom in the other room also shoots out a photon. Then the news hears about this and calls it teleportation. The photon never got teleported (that’s impossible) but some information got sent instantly through entanglement to the other atom. I hope this clears it up a bit.
  5. Nov 19, 2012 #4

    Jano L.

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    I found this video that might be interesting:


    It seems to me that the effect of "quantum teleportation" is the creation of correlations of detector clicks in lab A and B, by means of ordinary messaging and manipulations in both labs.

    Can anybody explain this better?
  6. Nov 19, 2012 #5
    Well, the authors of the original paper (see arxiv.org/abs/1211.2892) do claim that they are really doing teleportation, and the group is well known, so even if I haven't read the paper fully myself, I'm inclined to believe them.

    Also, to answer the OP, each Rubidium ensemble consists of 100 million atoms.
  7. Nov 19, 2012 #6
    The effect of quantum teleportation is to move quantum information from one place to another, while it gets destroyed in the first place. Why it is even necessary at all is because of the "no-cloning rule" in quantum physics, which states that no quantum information can be copied (in the sense of duplicated). This means that if you want to get the quantum information to another place you have to construct a process that simultaneously creates the information at the new place and destroys it at the old place. Such an algorithm has been found, and was, in order to create headlines, named Quantum Teleportation.
  8. Nov 19, 2012 #7
    I did not get all details from the paper, but as far as I understood, what they did was roughly the following:
    They created one ensemble of Rb atoms in a specified state (a spin wave), then they entangled this state with a photon. They entangled the second set of Rb atoms with aother photon and then the did a joint measurement on the two photons that entangled their state in such a way as to transfer the spin wave state from the first Rb-atom set to the second.
  9. Nov 21, 2012 #8
    Just for the purposes of finding out whether or not this trick can help us travel to the Andromeda galaxy which is 2.5 million light years away. To me, unless you can warp space, it seems like we will never get there. With quantum teleportation (let's just assume that if you teleport every atom of yourself to a new location and you destroy the original copy, you still will be able to think and act in your new location) you still can't get to the Andromeda because you would first have to carry the entangled atoms at a speed less than light to the galaxy before you can accomplish the teleportation, right?

    Also, about the fact that the rubidium ensemble is 10^8 atoms. What can you possibly do with 10^8 atoms? Surely they didn't "teleport" the ensemble of rubidium atoms, right? They just used it to spit out photons or something like that, right?
  10. Nov 21, 2012 #9
    No, thats right, quantum teleportation is not a teleportation of matter, it's a teleportation of information. As I mentioned in my previous post, the need for a scheme like this arises because quantum information cannot be copied, and the act of performing quantum teleportation is to move quantum information from one place to another. But yes, as you guessed, there does indeed have to be suitably prepared material on the new location already.
  11. Nov 21, 2012 #10
    G.Lemaitre, As Zarqon said ... data only. But don't dismiss it just yet. Imagine if you (or your robot rover) did make the journey and you needed to send back a message. (Potentially) quantum teleportation could accomplish that instantly. Imagine being able to communicate with the mars rover that quickly!


    Last edited: Nov 21, 2012
  12. Nov 21, 2012 #11
    Information cannot be transmitted instantly, only with a maximum velocity of c, and quantum information is no different. Note that in the quantum teleportation protocols, there is still a need to send classical information as a part of the algorithm, and these parts are obviously limited in the same way as all other classical information.
  13. Nov 21, 2012 #12
    Apologies Zarqon. You're correct.


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