Teleportation? Beam Me Up, But Do It Coherently?

This news article, led me to this website, describing a scheme (arXiv:0706.0062, “Teleportation of massive particles without shared entanglement” A. S. Bradley, M. K. Olsen, S. A. Haine and J. J. Hope) for transporting matter waves between two remote BECs. The basic idea is a setup where mater wave gets converted into information in photons which then gets written back onto another BEC. A very cool idea (if probably experimentally challenging!) However, in all of the above the articles, the experiment is described as “teleportation.” Now don’t get me wrong, I think the experiment would be very cool if you could pull it off, but does this type of setting really deserve the moniker of “teleportation”? Now normally I would call a setup like what they authors describe a quantum state transfer protocol and not teleportation. In teleportation you use entanglment and classical communication to transmit quantum information. In the above setting you swap the information from the matter wave to the light field and then back out again, with no use of entanglment or classical communication. The authors, probably sensing the existence of 32-year-old-curmudgeons like me, write

Although our scheme is quite distinct from what is normally termed quantum teleportation,
we feel that it is closer in spirit to the original fictional concept and so will use the term to describe our system.

Okay, so we could argue about this nomenclature until we turn ourselves into chemists. But the real question, I think, is not one of naming rights (although seeing as how the preprint is PRL pages long, and that damn APS journal is the king of the pedantic, there might be some interesting editor/author wrestling matches ahead.) No, the real question is whether the experiment described above is actually close in spirit to the original fictional concept!
So which is more like Star Trek teleportation? The teleportation ideas of Bennett et al. which use entanglement and classical communication or the “teleportation” ideas described above?

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11 Responses to Teleportation? Beam Me Up, But Do It Coherently?

  1. Aggie says:

    “Hm, would this require that James T. Kirk being supercooled before beaming?”
    Certainly this would be less challenging then interacting James T. Kirk with half of an entangled pair on a beamsplitter! 🙂
    To answer the question, I think the teleportation described in this article *is* closer in spirit to the teleportation in scifi movies but different to the teleportation described in physics. I think the “issues” really do come down to semantics and surely this could be fixed easily by redefining the two to be “quantum teleportation” and “star treck teleportation” or something to that effect rather than arguing over who’s teleportation is the “realer” teleportation (one came first in sci-fi and the other came first in sci). This reminds me of the gay marriage debate: but teleportation is defined for two particles which are entangled….!

  2. I think I agree with you. When I think of Star Trek transporters, I can’t see them using entirely quantum coherent links from the ship to the destination. The sci-fi fan in me wants to see farcaster portals, not teleportation, anyway.

  3. Wolf says:

    Hm, would this require that James T. Kirk being supercooled before beaming?

  4. Wolf says:

    Surely less challenging, but it looks like it would only work to teleport a dead Kirk’s coherent beam. So it would not qualify in my opinion to Star Trek standards.

  5. Perry says:

    None of them are teleportation in the Star Trek sense. In the TV show, Kirk is here, and then appears somewhere else. All of these schemes are state transfer schemes, in Bennet et. al. its not like there was an electron at Alice and none at Bob, and then at the end of the process Alice has no electron but Bob does. They both have electrons, and the state is transferred. Bennet’s scheme is such that you can transfer the state at a later time, but Alices measurement results telling Bob what to do, and it can be done later. Also it can be done over a distance without direct (quantum) interaction betweeen Alice and Bob. In this BEC scheme, like schemes like “stopped light” you have something like an adiabatic interaction that transfers a state from one system to another, but I’d say in both cases a state is transferred, and never is an object (massless or otherwise) killed at one place and created at another. Alice and Bob both have qubits, and here you have two BEC’s. All very cool stuff, but none of it is Star Trek teleportation IMHO.

  6. Wolf says:

    Yes, but the question was which one was “more like”, not equal to, Star Trek teleportation..

  7. Perry says:

    Wolf, I guess I think neither of them are really close! It’s like who was kinder, Stalin or Hitler….

  8. Murray Olsen says:

    The authors sensed the existence of curmudgeons of all ages but thought that this proposal had at least as much right to be called teleportation as the scheme of Bennett et al. If we accept that nothing in Star Trek violates the laws of nature, the beaming cannot be at superluminal velocities (OK, maybe the warp drive does :-)), which suggests that the best medium to connect the “sent” Kirk with the “received” Kirk would be light. And none of us could recall Scotty ever saying “The Bell state has been prepared, Captain. Ready to beam you to the surface.” Consider the above as being as much tongue in cheek as takes your fancy 🙂

  9. Wolf says:

    Perry, yes, but without some abstraction nothing could be compared at all. I’d suggest for this argument to consider generally a teleportation as a process where a system is deconstructed at location A and reconstructed at location B, and to add to the case of a Star Trek teleportation the only additional requirement that the system may be a living person.
    Under such properties, then it seems to me (but I’d call for the Pontiff position on this) that the Bennett et al. scheme is Star Trek-compliant at least in principle (ie ignoring the mind-blowing technological barrier), but that the Bradley et al. scheme is not (even in principle) since it requires BEC systems.
    (Murray: teleportation with shared entanglement may use light as well, to “beam” the classical bits)

  10. perry says:

    Wolf said
    >>
    I’d suggest for this argument to consider generally a teleportation as a process where a system is deconstructed at location A and reconstructed at location B, and to add to the case of a Star Trek teleportation the only additional requirement that the system may be a living person.
    >>
    Well I guess I’d say that in the Bennett scheme no system is deconstructed, in that I had a qubit before I did Bell measurements and called Bob, and still did afterwards. Now the STATE of the qubit is altered, and Bob’s qubit now has the state of the original particle given to Alice. So living person or chair, no matter is destroyed at one place and created at another in these schemes.
    If by system you mean state, then I’d be much more inclined to agree with you.
    As far as the Bradley scheme being specialized, that’s true, but all qubits have to have some physical representation, be it electrons, anyons, whateverons, so this doesn’t bother me too much. It seems much more akin to the slow/stopped light experiments than the Bennett scheme though.

  11. Wolf says:

    Yes, I was indeed meaning the state of a quantum system. Of course in both cases a reservoir of particles is needed at destination, but since they are fairly common, that should not be a problem.

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