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Teleportation — Fact and Fiction
jcatcw writes "Earlier this week actor Hayden Christensen, of Star Wars fame, and director Doug Liman discussed teleportation with MIT professors to compare the reality to the special effects version in the upcoming movie, Jumper. Edward Farhi, director of the Center for Theoretical Physics at MIT, said, 'It's a little less exotic than what you see in the movie. Teleportation has been done, moving a single proton over two miles. [But] teleporting a person? That is pretty far down the line. The quantum state of a living creature is pretty formidable. That is just not in the foreseeable future.'"
Whenever I see discussion about teleportation discussed, I think about Ilium and how in reality when they were teleporting, they were being killed and brought back to life at the other end, they were never the same person, made of the same atoms, just an exact copy.
If full-on analog teleportation using raw physics isn't possible in the short-to-mid term, what about recreation of a person at the endpoint?
What I mean by that, is you are able to identify what in a person's brain (and related nervous systems) that allows them to be their own unique person, and can store that as some kind of information, if that can be sent to a far-off location, to a reusable body or synthetic equivalent. This body could then perform the same role that the original would. You could afterwards read what changed in the meantime to find out what happened.
Of course, like all teleportation/copying ideas, it would challenge our definitions of what makes any of us unique, and the underlying nature of our definition of self.
Ryan Fenton
Here's an extremely simplified version of how Quantum Teleportation works. This model *will* break down if you push it too far, but it's a better model of the real physics than a Star Trek transporter.
1. Go out and buy two identical rubik's cubes.
2. Put them into identical configurations.
3. Send one to the other side of the planet.
4. Now, create any new configuration you want, but record the steps you take. (e.g. Rotate top 90 degrees left, etc.)
5. A person on the other side of the planet with the other cube can now recreate your cube precisely if you call them up and tell them the steps you took.
In quantum-land, there are some rather huge differences, which I'll talk about in a moment. However, the crucial thing to get out of this necessarily imperfect macroscopic example is that this kind of teleportation relies on preparing identical rubik's cubes in advance, classically transporting one of them to the receiver, and communicating via classical channels when actually performing the teleportation. At NO point can information travel faster than light (FTL). i.e. Quantum teleportation does *not* break causality. However, you will note that you can, potentially, communicate a very complex rubik's cube configuration with a very small ammount of classical data, provided you choose your initial state and operations intelligently.
The reality of Quantum Land (This will most likely confuse you. For that, I apologize.)
The pair of identically configured rubik's cubes are meant to be an analogy for an entangled pair, which is the most crucial thing to have in any quantum teleportation scheme. (You can make entangled pairs out of many things, such as photons or electrons. However, these things are typically tiny and simple. Complex Atoms, molecules, etc. don't work so well.) Where the analogy breaks down is entanglement, which is something we just don't see in macroscopic objects. The key idea behind entanglement is that you can place two things into a state that is not separable (i.e. You cannot describe one things state without also describing the other simultaneously), and any operation on one of them will have an effect on the other no matter how far separated the two things are. (NOTE: This does NOT allow FTL communication.) The problem is that quantum operations on entangled states are probabilistic rather than deterministic. If the sender performs operations, measurements really, on her half of the entangled pair and a new particle that is to be teleported, the receiver needs the results of those measurements to do anything useful, such as reconstruct the particle the sender had. Those results *must* be communicated from the sender to the receiver via classical channels.
Another big thing to note about quantum teleportation is that it, currently, is applied to indistinguishable particles. When you copy a rubik's cube, the copy is made up of complex molecules in a configuration that is unique. If you can magically examine the structure of any two real world rubik's cube you can tell them apart. They are distinguishable. A pair of photons in the same state, on the other hand, are indistinguishable. When you perform quantum teleportation, the copy that comes out at the sender's end is an absolutely perfect copy of the original because it has the exact state of the original and the particles themselves are not distinguishable. The state of the original, however, is changed when it is measured in the teleportation process, and there's no way to recover it. Effectively, the original is destroyed and a perfect copy comes out at the other end.
So there you have it. Quantum teleportation isn't really like a Star Trek transporter at all. It actually a lot stranger than that, and much more difficult to grok. (especially the entanglment part) Again, I apologize for not being able to come up with a way to explain entanglement without throwing a lot of math at you. (I'm not sure you can really understand it without the math.)
I've always had this nagging feeling that by disassembling your brain and moving it, that instant of consciousness would cease to be. You would actually die; in the destination pod, what is essentially a perfect clone is born with your memories. Of course, it would be seamless, and your teleported self wouldn't have any recollection of having died. This would also be impossible to prove, but it's what I choose to believe about this fictional device. Teleportation engineers kill humans!