there’s some quantum versions of algorithms that scale better than the digital version. ranging from quadratic to exponential speedup. Notably very fast at breaking currently widely used encryption. We are only saved by the fact quantum computers don’t have the required processing power to be feasible to use yet.

There’s some encryption algos that are thought to be resistant against quantum attacks but due to the above this isn’t actually proven yet, so currently any “post-quantum encryption” is currently a marketing buzzword with nothing behind it.