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Transportation Science

Scientists Teleport Information Between Ions a Meter Apart 220

erickhill writes with word that scientists from the University of Maryland have successfully transferred information from one charged atom to another without having it cross the intervening space of about one meter. The academic paper is available in the journal Science, though it requires a subscription to see more than the abstract. Scientists have previously teleported unmolested qubits between photons of light, and between photons and clouds of atoms. But researchers have long sought to teleport qubits between distant atoms. Light's high speed of travel makes photons good transporters of information, but for storing quantum information, atoms are a much better choice because they're easier to hold on to. 'This is a big deal,' comments Myungshik Kim, a quantum physicist at Queen's University Belfast in the United Kingdom. 'To store information as it is in quantum form, you have to have a teleportation scheme available between two stationary qubits. Then you can store them and manipulate them later on.'"
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Scientists Teleport Information Between Ions a Meter Apart

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  • by Chris Burke ( 6130 ) on Friday January 23, 2009 @09:33PM (#26584227) Homepage

    Well, I think that's roughly the essence of why you can't send information instantly. All information about the qubits is actually sent with the qubit itself as you separate them to whatever arbitrary distance you're going to do your 'teleportation' trick. It's a little less obvious to me exactly why that is... my understanding is that it's kinda like you have both a black and red marble and you send one around the world, well when one guy checks and sees that his marble is red, the other guy instantly knows that his marble is black. But the first guy doesn't get to pick black or red, and you always knew that the one marble would be the opposite color of the other, so you don't really know anything you didn't before.

    But I'm not really sure if what I'm saying there is even close to right.

  • by v1 ( 525388 ) on Friday January 23, 2009 @09:49PM (#26584381) Homepage Journal

    MPF. that's the most entertaining one-liner I've read in days...

  • by v1 ( 525388 ) on Friday January 23, 2009 @10:01PM (#26584459) Homepage Journal

    Although the state of one atom, once measured, will affect the other atom instantaneously, there's no possibility for FTL communication.

    The one part of that conclusion I don't get (and I've seen it several times to this point in the thread) is this: Why can't it relay binary information? If I entangle them, separate them, then either DO or DO NOT measure the first, and then measure the second, won't that tell me if the first one was measured or not?

    Hmmm thinking on this I have to ask for clarification on the purpose of the measuring. I was assuming when you say you measure it, it's an on/off kind of thing. Is it more correct to say that in my above scenario, the way to tell if the second measurement produces information, is to compare it to the measurement of the first? That makes more sense as to why it's a pointless exercise. Because after taking the second measurement, the measurement itself is not enough, you have to compare it with the first measurement? Which requires communication which you are trying to avoid?

  • Re:Bell's theorem (Score:3, Insightful)

    by blueg3 ( 192743 ) on Friday January 23, 2009 @10:09PM (#26584503)

    The teleportation is instantaneous. (A philosophy-inclined physicist might object to you applying the label "instantaneous", since it implies a signal is propagating instantaneously -- but there's no signal at all.) However, the teleportation cannot be used for communication without information transfer -- which means the communication is bound by the speed you can transfer that information (which is lightspeed).

  • Re:Mod patent up. (Score:4, Insightful)

    by tylerni7 ( 944579 ) on Friday January 23, 2009 @10:37PM (#26584661) Homepage
    I don't think that is how it works (although IANAP)

    If you check to see if a block you have is collapsed, then suddenly it becomes collapsed, even if it wasn't before. That means you can't tell what it was supposed to look like before.

    The other option is to only look at the entangled matter after you are sure it has collapsed, and see how the collapsing happened. However, this is also impossible. The way the qbits collapse is completely random, so you can't get any useful information out of reading them.

    The best way to think about it is you have two coins taped to each other head to tail or something.
    Then the coins are flipped, and separated without looking at them. Then take these coins to opposite ends of the universe.
    Now, as soon as one coin is observed, the value of the other coin is known as well. However, looking at either coin does not help to relay information. The only way to do that would be to know how the coin was going to land before looking at it. Or to be able to somehow observe the coin and know if the other has been observed.
  • by grumbel ( 592662 ) <> on Saturday January 24, 2009 @05:02AM (#26586681) Homepage

    The way I understand it:

    * you generate two entangled quantum things
    * you move them apart
    * you look at one of them and figure out its state, by that you knock it out of the superposition
    * magic happens and the (inverse of that) state is transported to the other thing
    * you look at the other thing an confirm that the state is as expected

    Since the stuff is in superposition you shouldn't be able to tell its state beforehand, but due to looking at the other thing an teleportation you can. The other thing has the inverse state thing since they must obey conservation of angular momentum (i.e. one spins up, then the other spins down).

    Now what I don't get is why this involves any 'teleportation' or quantum weirdness at all. Analog experiment:

    * you have two boxes
    * you put into one of those boxes a ball at random
    * you move them apart
    * you look into your box and can now tell if a ball is in the other box or not
    * no magic necessary, no teleportation happens, since the state of both boxes is fixed from the start

    I don't get why this teleportation thing is anything special, since as far as I understand it, its completly normal and matches exactly what you would expect.

Thufir's a Harkonnen now.