What would be some uses of this type of network? Would it be primarily for military purposes? Or financial transactions?
Basically everything.
Got to remember what the network is, and what it is suppose to do.
The network is suppose to transmit data. The problem here data loss. You know how sometimes we speak on a phone, a land line or cell phone, and the voice cuts out? That is data loss. There are various reasons, for that, electrical interference could be one of those factors. To make a long story short, they more or less solved the problem of transmitting data without errors.
Now that the network works, the next step is to make this network secure from hacking. An ongoing project.
Quantum communications is the next step in the evolution of networks, and looks like China will put into it in use in scale way before anyone else.