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Beating the standard quantum limit for force sensing with coupled two-mode optomechanical system



Xunnong Xu, Jacob Taylor


Optomechanics provides a method to transduce weak forces to optical fields, with many e↵orts approach the standard quantum limit. We consider force sensing using a mirror-in-the-middle setup and use two coupled cavity modes originated from normal mode splitting as pump and probe. We find that this two-mode model can be reduced to an e↵ective single-mode model, if we drive the pump mode strongly and detect the signal from the weak probe mode. The optimal force detection sensitivity at zero frequency (DC) is calculated and we show that we would be able to beat the standard quantum limit by driving the cavity close to instability. The best sensitivity achievable is limited by the thermal noise and how close to instability one can pump the system. We also find that the bandwidth where optimal sensitivity is maintained is proportional to the cavity damping. Finally, the squeezing spectrum of the output signal is calculated, and it shows almost perfect squeezing at DC is possible by using a high quality factor and low thermal phonon-number mechanical oscillator.
Physical Review Letters


optomechanics, force metrology, accelerometry, fabry-perot cavity, squeezing, standard quantum limit


Xu, X. and Taylor, J. (2014), Beating the standard quantum limit for force sensing with coupled two-mode optomechanical system, Physical Review Letters, [online], (Accessed May 19, 2024)


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Created October 20, 2014, Updated October 12, 2021