The Argonne quantum loop consists of a pair of connected 26-mile fiber-optic cables as 52 total miles.
They have begun to use the loop for a series of experiments, including transmitting signals from photons emitted from ensembles of ions. These ions can be used as a quantum memory for the network. A functional quantum memory, which entails the storage and retrieval of quantum states, is a key technological advance needed for quantum communication and a quantum internet. (SciTechDaily)