  We consider a cantilever mechanical oscillator(MO) made of diamond. There is
a nitrogen-vacancy(NV) center at the end of the cantilever. Two magnetic tips
induce strong second order magnetic field gradient near the NV center. Under a
coherent driving on MO, we find that the coupling between the MO and the NV
center can be greatly enhanced. We studied how to realize quantum state
transfer between MO and NV center and generate entanglement between them. We
also proposed a scheme to generate the two-mode squeezing between different MO
modes by coupling them to the same NV center. The decoherence and dissipation
effects for both MO and NV center are numerically calculated by taking the
present experimental parameters. It is found that high fidelity quantum state
transfer, entanglement generation, and large two-mode squeezing could be
achieved.
