Hedera is post-quantum secure for hashing and encryption, but not for signatures and key agreement.
The hashgraph consensus algorithm itself is post-quantum secure, as long as you use a post-quantum signature. We have designed our system to make it trivial to plug in a post-quantum signature scheme some time after the current NIST contest selects one or more.
In terms of relative security, the US government does not yet require post-quantum encryption for protecting its own top secret information, and are willing to wait a few years for NIST to finish. Hedera Hashgraph is following the same procedure.
We will be watching the progress on quantum computation very closely. We are years away from quantum computers becoming a real threat; however, Hedera can adapt quickly to unexpected changes.