So...
Decryption becomes much harder, but DOS becomes much easier?
A “quantum gadget” prototype capable of sending quantum keys using polarized light could make contactless payments on mobile more secure if it can be squeezed into a smartphone. The rise of contactless cards and apps such as Apple Pay and Android Pay have made it easier to make payments. Although swiping a card or smartphone …
when you're still using the same door hinges?
Somewhere, no matter how fancy you get, there is an "approval" sent and received.
That is the weak point.
But even easier, is to get on the backend and shuffle bits there. You can have all the guards and armored cars guarding your gold transactions but if you stuff them in a big vault that you "assume" is secure because you were told it was two decades ago, well, we see digital examples of that sort of thing all the time.
Or to take a classic movie scene, from the movie Sneakers. Robert Redford listens to all the fancy specs of a door lock-then defeats it simply by kicking it so either the bolt breaks or tears free of the jamb. We've done pen testing here simply by tapping out door hinge pins to open "secure" offices. All without a single password attempt made