We show that nitrogen-vacancy (NV) centers in diamond interfaced with a
suspended carbon nanotube carrying a dc current can facilitate a
spin-nanomechanical hybrid device. We demonstrate that strong magnetomechanical
interactions between a single NV spin and the vibrational mode of the suspended
nanotube can be engineered and dynamically tuned by external control over the
system parameters. This spin-nanomechanical setup with strong, \emph{intrinsic}
and \emph{tunable} magnetomechanical couplings allows for the construction of
hybrid quantum devices with NV centers and carbon-based nanostructures, as well
as phonon-mediated quantum information processing with spin qubits.Comment: Selected by PRL as "Editors' Suggestion
