  The efficient cooling of the nanomechanical resonators is essential to
exploration of quantum properties of the macroscopic or mesoscopic systems. We
propose such a laser-cooling scheme for a nanomechanical cantilever, which
works even for the low-frequency mechanical mode and under weak cooling lasers.
The cantilever is attached by a diamond nitrogen-vacancy center under a strong
magnetic field gradient and the cooling is assisted by a dynamical Stark-shift
gate. Our scheme can effectively enhance the desired cooling efficiency by
avoiding the off-resonant and unexpected carrier transitions, and thereby cool
the cantilever down to the vicinity of the vibrational ground state in a fast
fashion.
