Enhancing force sensing in a squeezed optomechanical system with quantum non-demolition measurement

Abstract A theoretical scheme is proposed to enhance the sensitivity of force sensor with 
quantum non-demolition measurement (QND) in an optomechanical setup assisted by four-tone optical driving
and an optical parametric amplifier (OPA). 
With the help of special drive, the system can be simplified as the typical type of QND for force sensing, 
so that the backaction noise can be evaded to surpass the standard quantum limit. Besides, the added noise can be suppressed 
owing to the modified optical susceptibility resulting from the OPA. 
By introducing two oscillators coupling with two charged bodies respectively,
the signal can be enhanced with the nonlinearity caused by Coulomb interaction, while the noise 
presents an exponential decrease. Moreover, considering the homodyne detection effect, the range of 
system parameters and frequency bands will be broadened.
The present investigation may provide a route toward simultaneously 
evading backaction noise, reducing the mechanical thermal noise, 
and enhancing the external signal, which can be an alternative design for sensitive devices.