Sub-standard-quantum-limit sensitivity via optical rigidity in the advanced LIGO interferometer with optical losses

The “optical springs” regime of the signal-recycled configuration of laser interferometric gravitational-wave detectors is analyzed taking into account optical losses in the interferometer arm cavities. This regime allows one 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 parameter values planned for the Advanced LIGO gravitational-wave detector, this restriction is insignificant.