While this might work for small networks, and indeed appears to provide a considerable increase in security there, I doubt that this can easily be extended to the whole internet – after all, the usual problem is not that some evil person peeks into an Ethernet cable, but rather that some router (at your ISP, the other party’s ISP or anywhere in between) is compromised. This approach effectively requires all routers (of the quantum messages, that is) to be ‘trusted nodes’.

So, cool, but, yeah…