Quantum Computers, if and when they work in practice, will break some algorithms, halve the 'bit-security' (e.g. 256 -> 128bit) of some algorithms, and leave the other quantum-safe ones untouched.

So encryption will still work in a quantum world. We 'just' have to update the algorithms we use.

See also: https://csrc.nist.gov/projects/post-quantum-cryptography/rou... https://en.wikipedia.org/wiki/Post-quantum_cryptography