I understand that quantum teleportation fidelity is the overlap of the initial q
ID: 1392028 • Letter: I
Question
I understand that quantum teleportation fidelity is the overlap of the initial quantum state with the teleported quantum state. If the teleportation is perfect, then the fidelity would equal 1 or 100% successful of retrieving the quantum state at the desired location.
In all real experiments I've glanced at and read thoroughly, the fidelities are never 1. Doesn't this suggest that what the experimenters "teleported" was really just a different state? Doesn't the fidelity have to be exactly 1 in order to really remove a quantum state from one location and make it appear at another location?
My concern is that either I've missed something, or that we aren't really teleporting at all because the final state achieved on the other side is not equal to the initial state!
Explanation / Answer
The ontological phrasing you use to describe quantum teleportation should be a red flag. There is no sense it which the quantum state "appears". It may be the case that you are confounding the physical system itself (real, ontological) with the quantum state assigned to it by the experimenter (subjective, epistemic). In other words, think of the quantum state as the information one has about a physical system and not the physical system itself.
If the fidelity between the final state and the input is not 1, then some operation in the protocol was not perfect. Of course, this will always be the case. So, you should understand "quantum teleportation" as the protocol itself and not the act of transferring exactly the quantum state of one physical system to another. For any practical application of the protocol, it need not be perfect to be useful.