  We describe how to prepare an electrically levitated nanodiamond in a
superposition of orientations via microwave driving of a single embedded
nitrogen-vacancy (NV) center. Suitably aligning the magnetic field with the NV
center can serve to reach the regime of ultrastrong coupling between the NV and
the diamond rotation, enabling single-spin control of the particle's
three-dimensional orientation. We derive the effective spin-oscillator
Hamiltonian for small amplitude rotation about the equilibrium configuration
and develop a protocol to create and observe quantum superpositions of the
particle orientation. We discuss the impact of decoherence and argue that our
proposal can be realistically implemented with near-future technology.
