AFAIK, it is teleportation -- something is going from one place to another without having to move through the space between them -- but it just isn't what you think of when you think of "teleportation".

Here is what I take to be an acceptable definition of teleporatation, which comes from Wikipedia:

Teleportation is the transfer of matter from one point to another without traversing the physical space between them

So under this definition, would you agree that quantum teleportation is not "regular" teleportation, since although information is traversing space without moving "through" it, matter is not?

I'm not really arguing semantics anymore, I'm just unclear whether the latter part of that question ("since...") is factually true, since I don't understand quantum stuff.

I think term teleportation is still valid because they can entangle and teleport any kind of particles. Photons are merely used because of their convenience.

You can entagled protons, electorns. Hell, I think they managed to demonstrate entanglement on a larger scale.

It seems to me like no particles are being teleported, becuse no matter is being moved. It's just information (i.e, the state of a particle) that is being duplicated in the same kind of particle on the other end.

If it is moving from A to B via some physical continuous medium, then it is not teleporting.

(Note: my full qualifications are an on-going Coursera course on quantum computing that covers quantum teleportation lightly. FWIW, I recommend the course.)

In vague terms, the process of quantum teleportation is the following:

* You have a qubit that you want to transmit to a friend and that you don't know anything about.

* create an entangled pair of qubits (such as photons) and separate them. Keep one yourself and give another to your friend.

* Now you have two qubits; one entangled with your friends and one that you want to transmit.

* Send your two bits through a quantum circuit (the main part being a 'controlled NOT gate').

* Your bit is now entangled with the bit that is entangled with your friends bit.

* Measure each of your bits, hence 'collapsing' them. Each measurement gives you a classical bit.

* Transmit your two classical bits to your friend over any classical connection.

* Your friend then performs an operation on his or her qubit depending on what you send him or her.

* Your friend's qubit is now in the state that your original qubit was in. Your original qubit is now in a different state.

Call it teleporation if you want; it's not that unlike some sci-fi teleportation constructs of 'beaming' things places.

Why bother with this?

* It lets you send qubits to distant places that you have only classical channels to (and previously close enough contact share two entangled qubits).

* It allows more error-resistant computations: if your qubit is difficult to construct and you wish to perform a difficult operation on it, you can actually have your friend perform the difficult operation on his or her bit - prior to teleportation - and, if it succeeds, you can then proceed with the teleportation. If it doesn't succeed, your friend may try again on another entangled qubit without messing up your difficult-to-prepare qubit. After a success and teleportation, you get the same result (up to a commutator which is usually relatively small and risk-free) as performing the difficult operation on the difficult-to-prepare qubit, but with less risk of messing it up.

After this process is completed, can the entangled qubit pair be reused to transfer more information or is this a one off? That is, do you have to repeat the "give another to your friend" part in order to transmit more information?

This method requires the initial entangled qubits to be in a "Bell State" (equal superposition of both in 0 and both in 1). After teleportation, its no longer in that state. So it's not reusable by this method, but maybe by another that I don't know about (though I doubt it).

Thanks, this is a pretty helpful summary.

Can you clairify the second reasons to "bother" with it? I mean, if it's difficult for me to perform the operation, it's presumably equally difficult for my "friend" to do it (and subsequently "teleport" the result to me), so why not just do it myself?

In addition to the transportation benefit, it can be used for computation. The example given in the Coursera course was to suppose that we have a qubit (quantum bit) Y on which we wish to perform some unreliable computation. If it fails, then Y's state is lost. Further suppose that Y is costly (e.g. time consuming) to re-create.

Instead, we can create a pair of entangled qubits (which is easy to do - just a single quantum gate), as one would when teleporting a qubit. We then apply the computation to one of these qubits, and try again with a new pair of qubits if it fails.

Once we have successfully applied the computation, we can teleport our "expensive" qubit Y using this entangled pair. The result is that we now have Y with the computation applied, but there is no risk of losing Y's state.

The details are rather more tricky (only certain computations can be used, some require a correction after teleportation etc.), but this basis can (and has) be built on to develop, for example, fault tolerant quantum computing.

What silverdrake said, but also it's a matter of error-tolerance. If we want to do a difficult two-step computation and know when each sub-step succeeds or fails, than:

1) Perform the first step on a qubit (repeat if failed)

2) Your friend performs the second step on their qubit (repeat if failed, but no need to repeat (1))

3) Teleport your qubit to your friend

4) Your friend performs a simply operation on their qubit

After this, the state of your friend's qubit is now the result of applying both operations. But each sub-step can be redone without affecting the result of the other, so mistakes are easier to correct. So in this case, "your friend" might refer to yourself - the important part isn't teleporting the qubit somewhere elses, it's that the computation is less error-prone.

Perhaps, you are working on an important experiment with your qubit. However, you realize that that you need an expensive piece of lab equipment to follow through.

However, you remember that your "friend" has this equipment at his/her lab. You also happen to share an entangled qubit with your friend. And you know that you can call your friend on the phone.

Rather than mail the qubit to your friend's lab which could be in a very remote location, you use quantum teleportation to send its state.

This way your friend receives your qubit without the qubit having traveled through physical space.

It may be that the information encoded in the spin of a photon or something has jumped non-continuously. But most people think of "teleportation" as transferring matter.

I guess the realization that energy/information and matter is the same thing came after the term teleportation was coined also?