Third and final post in a series about "teleportation" from July 2002. This one is mostly dedicated to voicing the same complaints I have about the more recent stories that kicked this whole repost business off.
The more things change, the more I keep repeating myself.
So, having discussed how to do "quantum teleportation," how does this get us to "Beam me up, Scotty?" Well, that's the thing. It doesn't, not in any meaningful sense. What gets "teleported" is just the state of the initial quantum particle, not the particle itself. There's no reason why you couldn't do "teleportation" with atoms instead of photons (indeed, that's the next stated goal of the experimenters in the field), but again, all you're "teleporting" is the state of the atoms, not the atoms themselves. To "teleport" a person by this method, you'd need to already have a gigantic person-sized collection of the appropriate atoms at Bob's house, and copy the quantum state of the original patron of Alice's Restaurant onto those atoms.
It's also not true that "teleportation" inherently requires the destruction of the initial object, as is sometimes claimed. For photons, this happens to be true, as most photon measuring schemes involves the destruction of the photon, but the only thing that's necessarily destroyed is the quantum state of the original. If you were to do "teleportation" of an atom, the original atom would still be sitting in the lab at the end of the experiment, it'd just be in a different state than when you started.
This is why I put "teleport" in scare quotes throughout these articles. The process is almost completely unlike what we think of as teleportation: as most people picture it, teleportation involves atoms which start out at Point A disappear from there, and re-appear at Point B. All that really moves in this scheme is information about the quantum state, and it's not even clear that that matters, as noted by an IBM researcher. (You can imagine doing the experiment with a pair of atoms in the EPR state, rather than photons, which would give you a sort of trivial motion of atoms from one place to another. The more sensible way to "teleport" atoms, however, would be to use photon pairs, entangle them with the source atom, and transfer the atomic state to another atom.) It's not without technological possibilities-- this sort of thing could have implications in quantum computing, and possibly for what Jeff Kimble at Caltech likes to call the "quantum internet," a hypothetical future network of quantum computers-- but this isn't a clear route to sci-fi matter transmission.
This is another example of good work being over-sold. I'm not claiming that the research is uninteresting, or unimportant-- these experiments are really fascinating, and add to our understanding of the weirdness at the heart of reality-- just that the terminology creates an unrealistically inflated impression of the work. It's the scientific equivalent of political spin. Calling this "teleportation" is a wonderful way to get yourself in the New York Times and on the evening news, but the word carries a host of connotations that just don't fit with the actual experiment, and those connotations lead directly to endless Star Trek references, and things like the author of the original article speculating grandly that we'll be hopping between parallel universes any day now. That sort of boundless techno-optimism is vaguely charming, but it's misplaced, due to the unfortunate terminology. The work itself is impressive enough on its own; the Star Trek stuff is gilding a lily that, scientifically, doesn't need the help.
To their credit, most of the scientists involved try to distance themselves from such claims (some more emphatically than others, but they all at least hedge their bets). The problem is that the unfortunate name given to the process plants the idea in the minds of techno-enthusiasts and "futurists," and sticks the rest of us with dealing with the connotations and Star Trek questions.
(I should note that there are plenty of other problems with the Vegas article. The (sketchy) description of the process is slightly garbled in a manner that suggests the author is more a techno-enthusiast "nerd groupie" than an actual nerd. I don't want to give the impression that it's a good explanation of the issues involved-- most of the other links I've provided above and below do a better job. The Vegas City Life article happened to start me thinking about this stuff, leading to these posts, and that's all.)
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