Broadband dichromatic variational measurement

Standard Quantum Limit (SQL) of a classical mechanical force detection results from quantum back action impinged by the meter on probe transducer perturbed interest. In this paper we introduce technique continuous \vy{broadband} avoiding measurements for case resonant signal acting linear oscillator supporting one mirrors an optical Michelson-Sagnac Interferometer (MSI). The interferometer with movable mirror is opto-mechanical able to support polychromatic field. method involves dichromatic MSI modes and having frequency separation equal frequency. We show that analyzing each harmonics reflected system separately postprocessing measurement allows excluding in broad band measuring sensitivity better than SQL.