DrChinese said:
Well I mostly agree with the above,but again don't see the relevance to the OP's question (which was what I was addressing).
Well, OP was asking about quantum teleportation and your response had nothing to do with teleportation. So correcting it was very relevant.
Teleportation is highly constrained (to what can be measured simultaneously) and requires classical information to make anything of what you teleported. You do NOT teleport a specific known state, you teleport one of several possible states; I guess you are correct to call it teleportation once the classical signals arrive and you put it all together.
Teleportation, by definition, is not completed until the classical information has arrived and been implemented. You seem to be assuming the original poster was asking about instantaneous teleportation of states. I see no such assumption in the original post. Quantum teleportation is not about doing something here and instantaneously having something happen there. Classical communication to complete the exchange, whether it's photons or OP's question about whole atoms, is assumed. That's not what
I call teleportation it's what
everyone in quantum information calls it. You
do teleport a particular state, not a mixture, because the teleportation is not complete until Bob learns the results of Alice's measurement and modifies accordingly. You are using very standard terminology incorrectly.
Of course position *and* momentum cannot be teleported, I am sure you mean position OR momentum.
Again, huh?
States are teleported, not particular observables associated with states, so this comment doesn't even parse. One doesn't teleport "position" and "momentum". You teleport states that
have some particular position and momentum representations (though, again, I'm not sure if teleportation has been shown to work in infinite dimensional Hilbert spaces—that is what I meant when I said I don't know if this works for position and momentum). Complementary observables, which it sounds like you're connecting this to, have nothing to do with this.
A system of more than one particle (such a nucleus) would be far more complex to analyze and constraints on knowledge would prevent you from getting very close to describing it as it sits
Once again, the entire
point of teleportation is that you
don't have the analyze the state you're trying to send. It is a method to allow you to move a state from A to B, without physically carrying it there and without having to know what state it is!
This is extremely frustrating. It's really clear you don't know what teleportation is about, but you're continuing to insist you've understood and answered OP's question. I think someone with the "Science Advisor" tag has the responsibility of not trying to speak authoritatively on topics they are unfamiliar with. There's nothing wrong with being unfamiliar with something, but just kind of making it up as you go is not acceptable. There are plenty of good resources to explain how quantum teleportation works and I think you should read some before contributing any more to this thread.Yash, If the goal is just to have Alice teleport, say, a helium nucleus in a particular state to Bob and Bob
has a helium nucleus onto which the state can be teleported, then I think the answer is probably yes. I think that might not be your question, though. It sounds like you're wondering whether or not the same techniques that let you move, say, a particular polarization state from one photon to another could be used to transport whole particles. In other words, what if Bob doesn't even have a helium nucleus, he just has some raw material that he make interact relativistically. Can Alice and Bob do something like teleportation with atom smashers of a sort such that if Alice wants to send Bob an electron or proton or a helium nucleus, then at the end of their protocol an electron or a proton or a helium nucleus pops out of Bob's machine. It's a very interesting question and I don't think anyone has the definite answer right now but I suspect it's probably no (though for very different reasons than DrChinese has been saying).
I think the biggest challenge, even if the techniques of quantum teleportation generalize sufficiently, is control over the states. If you're sending a spin-1/2 state, you need to be apply an arbitrary set of unitary operators to it and the entangled pair. Fortunately, applying arbitrary unitary operations to it is feasible (though not easy, ask the quantum computing people!). In particle physics, we don't have the same sort of Hamiltonian control. So, we generally can't, say, take a couple protons, smash them together very carefully, and get exactly the particles we want out at the end, we get a distribution of particles. Whereas with non-relativistic quantum mechanics, we can often tune the time evolution of the system how we like, in relativistic quantum mechanics (the regime where massive particles can be created) we're generally stuck with what nature gave us.
