I'm no expert in quantum computation but my understanding is that using qubits for quantum computing is totally different to using qubits to exchange secrets as in cryptographic key exchange. The latter is using the property that observing the quantum state changes the state, thus an eavesdropper can't interfere when you send qubits over the wire to exchange a secret. That seems very different to arranging large amounts of qubits in a particular way to do useful calculations.

Even in the key exchange case, I'm personally pretty skeptical of its real-world usefulness because it's not really solving a problem we actually have: public key cryptography (even slower post-quantum variants) work just fine and seem a bit more practical than building some quantum infrastructure to send entangled qubits over to augment a secret that's already exchanged.