Cooling a micro-mechanical resonator to its ground state by measurement back-action

TL;DR

This paper analyzes how measurement back-action can be used to cool a micro-mechanical resonator to near its ground state by extracting information and reducing entropy, despite the coupling not directly causing cooling.

Contribution

It demonstrates that measurement-induced back-action can effectively prepare the resonator in a near-ground state through information extraction and state conditioning.

Findings

Resonator states become close to coherent states conditioned on measurements.

Measurement back-action can be harnessed for cooling without net energy transfer.

The approach enables displacement to the oscillator ground state.

Abstract

We present an analysis of the cooling of a micro-mechanical resonator by means of measurements and back action. The measurements are performed via the coupling to a Cooper-pair box, and although the coupling does not lead to net cooling, the extraction of information and hence entropy from the system leads to a pure quantum state. Under suitable circumstances, the states become very close to coherent states, conditioned on the measurement record, and can hence be displaced to the oscillator ground state.