Negative radiation pressure scheme for simultaneous suppression of arduous back-action evasion and shot noise in gravitational wave detectors

Aiming at applications for gravitational wave (GW) detection, in particular at the reduction of quantum back action noise, we propose a novel scheme how to obtain back action evading measurements performed on an opto-mechanical cavity, by introducing a negative radiation pressure coupling between the cavity field and the end mirror. The scheme consists of introducing a double cavity with end mirrors interlocked by a pivot and moving in opposite directions. The measurement is performed by sending a two-mode squeezed vacuum to both cavities and detecting the output through the heterodyne detection. Compared to the previously proposed hybrid negative mass spin-optomechanical system in Khalili and Polzik (2018 Phys. Rev. Lett.121 031101), we see that our scheme is capable to suppress back action noise by nearly two orders of magnitude more in the lower frequency region. Overall, the setup has been able to squeeze the output noise below the standard quantum limit, with more efficiency. The scheme has also proven to be beneficial for reducing thermal noise by a significant amount. We confirm our result by a numerical analysis and compared it with the previous proposals (Khalili and Polzik 2018 Phys. Rev. Lett.121 031101).