I’d always been lead to believe that quantum computers could potentially kill classic cryptography. In the first instance it’s pretty reassuring that find out that this is not entirely the case. In the second it’s good to know that it’s not the case at all for some alternative approaches to cryptography:
Research is also being done into what is often called post-quantum cryptography, although a more precise name might be quantum-resistant cryptography. These are systems running on ordinary computers but based on problems that are not in the hidden subgroup category. These problems include solving systems of multivariable polynomials, finding the shortest distance from a point to an n-dimensional skewed grid of other points, and finding the closest bit string to a set of other bit strings.
TLDR: Some classes of (useful) problem are about as hard for quantum computers are they are for regular computers.