Ground-state cooling of a levitated nanoparticle

Controlling a mechanical degree of freedom in the quantum regime is a prime goal of technological relevance (e.g., in the context of quantum signal transduction) and for fundamental research (e.g., to test quantum mechanics at a macroscopic scale). An ideal starting point for these endeavors is the ground state of a harmonic oscillator. Measurement-based quantum control requires that the coupling between the measurement apparatus and the system under control exceeds the coupling of the system to the thermal bath. In other words, when the measurement backaction dominates the decoherence of the mechanics, the measurement record can be exploited to exert quantum control.