The hash function used for proof-of-work is, but the signature schemes for authenticating transactions aren't. So you can't make a bunch of counterfeit bitcoins out of thin air, but you can steal other people's bitcoins, which isn't really better.
Otoh, afaik either it wasn't like this in the satoshi era or satoshi revealed the public key. In any case, satoshi's wallets are crackable by qc.