Improving the cooling performance of a mechanical resonator with two-level-system defects

We study the cooling performance of a realistic mechanical resonator containing defects. The normal cooling method through an optomechanical system does not work efficiently due to those defects. We show that, by employing periodical σz pulses, we can eliminate the interaction between defects and their surrounding heat baths up to the first order of time. Compared with the cooling performance of the no σz pulses case, much better cooling results are obtained. Moreover, this pulse sequence has the ability to improve the cooling performance of the resonator with different defect energy gaps and different defect damping rates.