  Emerging quantum technologies require precise control over quantum systems of
increasing complexity. Defects in diamond, particularly the negatively charged
nitrogen-vacancy (NV) center, are a promising platform with the potential to
enable technologies ranging from ultra-sensitive nanoscale quantum sensors, to
quantum repeaters for long distance quantum networks, to simulators of complex
dynamical processes in many-body quantum systems, to scalable quantum
computers. While these advances are due in large part to the distinct material
properties of diamond, the uniqueness of this material also presents
difficulties, and there is a growing need for novel materials science
techniques for characterization, growth, defect control, and fabrication
dedicated to realizing quantum applications with diamond. In this review we
identify and discuss the major materials science challenges and opportunities
associated with diamond quantum technologies.
