When is Quantum State Teleportation useful?

Question

I've been working through the Brilliant Course on Quantum Computing, and I've reached the lesson on Quantum Teleportation. After completing the lesson and reading several questions and answers here:

1. quantum teleportation,
2. Is quantum teleportation really teleportation?,

I'm still struggling to understand its purpose.

If I understand the idea correctly, Quantum State Teleportation works in the following way:

A qubit represents infinite information because it can be in infinite states. Because of this, it's impossible to communicate a qubit state in a purely classical way.

However, a state can be "teleported" by entangling two qubits, A and B, and giving one to Alice and one to Bob. Then Alice can entangle a further qubit, C, with A via a Bell State measurement and send the results to Bob classically.

That allows Bob to apply his own measurement that recreates the state Alice's qubit C was originally in before the Bell State measurement.

Apparently, the reason to do this is to avoid thermal decoherence. That makes sense, but surely the entangled qubits A and B are just as susceptible to thermal decoherence?

If that's the case why not send C directly?

Answer 1

One scenario is that the qubit C is of superconductor type, which is not good for transmitting long distance, and qubit B is of photon type and is good for long distance transmission. Hope this answer helps.

Answer 2

One possible use is to separate sending a qubit from sending information.

For example, suppose you were building a quantum computer with multiple nodes. You could populate the nodes with entangled qubits before run-time. That way, when it becomes necessary to transmit quantum information during run-time you could simply send classical bits.