Over the last two decades there have been dramatic advances in the development of solid state qubits in diamond that can store quantum information and communicate quantum information optically. These qubits can form the basis of new technologies, such as quantum computers and quantum repeaters. We are constructing a quantum link to probe distributed quantum entanglement, with nodes at Argonne and Fermilab. We will optimize qubits in diamond for integration with the link. We have developed methods to make ultrathin membranes of diamond, which opens new pathways to engineer and control quantum defects. With this platform, we will simultaneously control the charge state and emission energy of quantum defects, while also efficiently optically interfacing the defects with nanophotonics, which the promise of many orders of magnitude improvement over existing technologies. We will also explore engineering the mechanical properties of diamond to improve quantum and optical coherence.