Citation needed? Symmetric encryption algorithms like AES (with at least 256 bit key) are considered safe even against quantum computers, based on some reasonable math/qm assumptions.

Yeah, so far as I know the only algorithm that provides an asymptomatic speedup (for AES or similar symmetric key crypto) over a classical computer is Grover's algorithm. That would reduce a 256 bit key to 128, which is hardly disastrous.

All of that seems to only be “medium” secure in face of future quantum computing.

“It's been estimated that 6,681 qubits would be required to run use Grover's algorithm to break AES-256 bit encryption.”

https://www.theregister.co.uk/2019/03/14/quantum_encryption_...

Not only that, there are asymmetric encryption algorithms not vulnerable to Shor's algorithm, we're just not using them yet (because they're slower and haven't been as well-studied as RSA or ECC).

Obvious counterexample: one-time pads.

Even if you don’t go that extreme, there’s no indication that e.g. AES is breakable.

What do you mean with quantum encryption? QKD (Quantum Key Distribution)?

Though the concept seems nice, it has quite a few issues in practice. Such as distance between coupled devices, and the need to have a dedicated physical communication line.

Oh and before you think you can just chain several devices to get longer distances: this opens you up to classical MitM attacks.

Source: https://www.nature.com/articles/npjqi201625