Cooling a Mechanical Resonator to Quantum Regime by heating it

TL;DR

This paper demonstrates a counterintuitive cooling method for a diamond-based mechanical resonator, where increasing the thermal bath temperature of one mode results in significant cooling of another mode to the quantum regime.

Contribution

The study introduces a novel cooling technique leveraging heating of one mechanical mode to cool another, supported by numerical simulations and physical explanations.

Findings

Cooling of mode b increases with higher bath temperature of mode a

Quantum regime cooling conditions are identified and confirmed

Numerical simulations validate the counterintuitive cooling effect

Abstract

We consider a mechanical resonator made of diamond, which contains a nitrogen-vacancy center (NV center) locating at the end of the oscillator. A second order magnetic gradient is applied and inducing coupling between mechanical modes and the NV center. By applying proper external magnetic field, the energy difference between NV center electron spin levels can be tuned to match the energy difference between two mechanical modes $a$ and $b$. A laser is used for continuously initializing the NV center electron spin. The mode $a$ with lower frequency is driven by a thermal bath. We find that the temperature of the mode $b$ is significantly cooled when the heating bath temperature is increased. We discuss the conditions that quantum regime cooling requires, and confirm the results by numerical simulation. Finally we give the intuitive physical explanation on this unusual effect.