If quantum computers crack digital crytography, traditional bank account goes to zero too because regular 'ol databases also use crytography techniques for communication.
If all else fails, banks can generate terabytes of random one-time pad bytes, and then physically transport those on tape to other banks to set up provably secure communication channels that still go over the internet.
It would be a pain to manage but it would be safe from quantum computing.
This is WRONG and a very common stupid belief. Traditional banks will just transfer easily to safer encryption, since they are centralised. Bitcoin won't. Bitcoin will die and world will undergo infinite suffering.
