We study cooling and squeezing the fluctuations of a nanomechanical beam using quantum feedback control. In our model, the nanomechanical beam is coupled to a transmission line resonator via a superconducting quantum interference device (SQUID). The leakage of the electromagnetic field from the transmission line resonator is measured using homodyne detection. This measured signal is then used to design a quantum-feedback-control signal to drive the electromagnetic field in the transmission line resonator. Although the control is imposed on the transmission line resonator, this quantum-feedback-control signal indirectly affects the thermal motion of the nanomechanical beam via the inductive beam-resonator coupling, making it possible to cool and squeeze the fluctuations of the beam, allowing it to approach the standard quantum limit.
@article{arxiv.0902.2526,
title = {Cooling and squeezing the fluctuations of a nanomechanical beam by indirect quantum feedback control},
author = {Jing Zhang and Yu-xi Liu and Franco Nori},
journal= {arXiv preprint arXiv:0902.2526},
year = {2009}
}