I thought about this also. A true Quantum computer could end the current bitcoin system. Even though it is only theoretical now. The speed of development is impressive. A system for sending messages using wave collapse already exists!
"Please explain, How?
As I see it, you would need to crack the Key Pair almost instantaneously before it got added to the chain, if another Key pair is then generated before the next transaction..."
"But if Quantum Computing becomes prevalent so would Quantum Pairing. No one would be able to see the transaction or intercept it between parties."
Wooah. Thats a good way to do it. It won't work every time, but you could break some keys before they are added to the chain, right? And you have a solution! Add quantum entanglement to the system and you could verify a transaction, perhaps before sending it to any nodes.