Sub-SQL Sensitivity via Optical Rigidity in Advanced LIGO Interferometer   with Optical Losses
  The ``optical springs'' regime of the signal-recycled configuration of laser interferometric gravitational-wave detectors is analyzed taking in account optical losses in the interferometer arm cavities. This regime allows to obtain sensitivity better than the Standard Quantum Limits both for a free test mass and for a conventional harmonic oscillator. The optical losses restrict the gain in sensitivity and achievable signal-to-noise ratio. Nevertheless, for parameters values planned for the Advanced LIGO gravitational-wave detector, this restriction is insignificant. 
F.Ya. Khalili, V.I. Lazebny, S.P. Vyatchanin