  We propose an optimization scheme for ground-state cooling of a mechanical
mode by coupling to a general three-level system. We formulate the optimization
scheme, using the master equation approach, over a broad range of system
parameters including detunings, decay rates, coupling strengths, and pumping
rate. We implement the optimization scheme on three physical systems: a
colloidal quantum dot coupled to its confined phonon mode, a polariton coupled
to a mechanical resonator mode, and a coupled-cavity system coupled to a
mechanical resonator mode. These three physical systems span a broad range of
mechanical mode frequencies, coupling rates, and decay rates. Our optimization
scheme lowers the stead-state phonon number in all three cases by orders of
magnitude. We also calculate the net cooling rate by estimating the phonon
decay rate and show that the optimized system parameters also result in
efficient cooling. The proposed optimization scheme can be readily extended to
any generic driven three-level system coupled to a mechanical mode.
