Classical demonstration of frequency dependent noise ellipse rotation   using Optomechanically Induced Transparency
  Cavities with extremely narrow linewidth of 10-100 Hz are required for realizing frequency dependent squeezing to enable gravitational wave detectors to surpass the free mass standard quantum limit over a broad frequency range. Hundred-meter-scale high finesse cavities have been proposed for this purpose. Optomechanically induced transparency (OMIT) enables the creation of optomechanical cavities in which the linewidth limit is set by the extremely narrow linewidth of a high Q factor mechanical resonator. Using an 85mm OMIT cavity with a silicon nitride membrane, we demonstrate a tunable linewidth from 3Hz up to several hundred Hz and frequency dependent noise ellipse rotation using classical light with squeezed added noise to simulate quantum squeezed light. The frequency dependent noise ellipse angle is rotated in close agreement with predictions. 
Jiayi Qin, Chunnong Zhao, Yiqiu Ma, Xu Chen, Li Ju, and David G. Blair
quant-ph