Squeezing for broadband multidimensional variational measurement

Broadband multidimensional variational measurement allows overcoming the standard quantum limit (SQL) in detecting a classical mechanical force acting on a mechanical oscillator. In this measurement quantum back action, which perturbs the evolution of a mechanical oscillator, can be completely removed in a broad frequency band after post-processing. In this paper we show that optical losses inside the cavity restrict back action exclusion due to the loss noise. We also analyze the effect of two-photon (nondegenerate) and conventional (degenerate) squeezing in order to improve sensitivity with accounting for optical losses. We consider mainly internal squeezing.