If you want truly unbreakable encryption, there's always the one-time pad. In that case, the unbreakability is guaranteed by mathematics, an even stronger guarantee than physics.

Certainly, the one-time pad suffers from the need of each pair of parties to exchange keys beforehand. As far as I can see, the problem is just as bad for quantum crypto or this thermodynamic crypto because you have to arrange a fiber optic cable, a laser line of sight, or a copper wire between each pair who want to communicate.

You can't use quantum crypto or this thermodynamic crypto on the Internet for example. You need to set up unshared exclusive-use connections between each of the parties.

If you're going to the trouble of doing that, you might just as well exchange some terrabyte disks of one-time pad data, and you'll achieve the same (or greater) guarantee of security.