Feedback cooling of cantilever motion using a quantum point contact transducer

TL;DR

This paper demonstrates feedback cooling of a micromechanical cantilever's motion using a quantum point contact as a displacement sensor, achieving significant temperature reduction and high displacement resolution at low temperatures.

Contribution

It introduces a novel method of using a quantum point contact in an active feedback loop to cool and measure cantilever motion at cryogenic temperatures.

Findings

Minimum effective mode temperature of 0.2 K achieved

Displacement resolution of 10^(-11) m/Hz^(1/2)

Noise squashing observed at high gain

Abstract

We use a quantum point contact (QPC) as a displacement transducer to measure and control the low-temperature thermal motion of a nearby micromechanical cantilever. The QPC is included in an active feedback loop designed to cool the cantilever's fundamental mechanical mode, achieving a squashing of the QPC noise at high gain. The minimum achieved effective mode temperature of 0.2 K and the displacement resolution of 10^(-11) m/Hz^(1/2) are limited by the performance of the QPC as a one-dimensional conductor and by the cantilever-QPC capacitive coupling.