NP Problem that cannot be solved by a quantum computer in polynomial time Is there any NP-Problem that can't be (maybe even proven) solved by quantum computers. I'm not talking about quantum NP-Problems (if that's even a thing), but about normal NP.
If that NP Problem exists could you also use it for cryptography, since I don't want to buy a quantum computer just to be secure.


EDIT:
I'm not talking about NP-complete, because that would have no use (I think) in cryptography and also not about symmetric key encryption.
Nobody really knows whether quantum computers can solve all NP complete problems in polynomial time or not. There is strong evidence that they cannot: Strengths and Weaknesses of Quantum Computing, but no definite proof.