Cooling a mechanical resonator via coupling to a tunable double quantum dot

Abstract

We study the cooling of a mechanical resonator (MR) that is capacitively coupled to a double quantum dot (DQD). The MR is cooled by the dynamical backaction induced by the capacitive coupling between the DQD and the MR. The state transition between the two dots of the DQD is excited by an ac field and afterward a tunneling event results in the decay of the excited state of the DQD. An important advantage of this system is that both the energy-level splitting and the decay rate of the DQD can be well tuned by varying the gate voltage. We find that the steady average occupancy, below unity, of the MR can be achieved by changing both the decay rate of the excited state and the red-detuning between the transition frequency of the DQD and the microwave frequency, in analogy to the laser sideband cooling of an atom or trapped ion in atomic physics. Our results show that the cooling of the MR to the ground state is experimentally implementable. Also, the MR can be heated and the steady-state average occupancy becomes infinite when the microwave frequency is larger than the transition frequency of the DQD (i.e., the blue-detuning).