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Re:Quantum teleportation over 143 kilometres using active fe... by javert on Sunday September 09, 2012 @02:52AM (#4495147)
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?

Re:Quantum teleportation over 143 kilometres using active fe... by stordoff on Sunday September 09, 2012 @04:44PM (#4496915)
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.

Re:Quantum teleportation over 143 kilometres using active fe... by tgb on Sunday September 09, 2012 @11:55AM (#4496057)
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.

Re:Quantum teleportation over 143 kilometres using active fe... by silverdrake11 on Sunday September 09, 2012 @09:40AM (#4495745)
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.