  There has been rapidly growing interest in hybrid quantum devices involving a
solid-state spin and a macroscopic mechanical oscillator. Such hybrid devices
create exciting opportunities to mediate interactions between disparate qubits
and to explore the quantum regime of macroscopic mechanical objects. In
particular, a system consisting of the nitrogen-vacancy defect center in
diamond coupled to a high quality factor mechanical oscillator is an appealing
candidate for such a hybrid quantum device, as it utilizes the highly coherent
and versatile spin properties of the defect center. In this paper, we will
review recent experimental progress on diamond-based hybrid quantum devices in
which the spin and orbital dynamics of single defects are driven by the motion
of a mechanical oscillator. In addition, we discuss prospective applications
for this device, including long range, phonon-mediated spin-spin interactions,
and phonon cooling in the quantum regime. We conclude the review by evaluating
the experimental limitations of current devices and identifying alternative
device architectures that may reach the strong coupling regime.
