Optomechanical detectors have reached the standard quantum limit in position and force sensing where measurement backaction noise starts to be the limiting factor for the sensitivity. A strategy to circumvent measurement backaction and surpass the standard quantum limit has been suggested by M. Tsang and C. Caves [Phys. Rev. Lett. 105, 123601 (2010)]. We provide a detailed analysis of this method and assess its benefits, requirements, and limitations. We conclude that a proof-of-principle demonstration based on a micro-optomechanical system is demanding but possible. However, for parameters relevant to gravitational-wave detectors, the requirements for backaction evasion appear to be prohibitive. © 2014 American Physical Society.
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