Source: National Natural Science Foundation of China

Grant No:91636220

Project: Beating the classical limit in weak force measurement using squeezed state of a micro-mechanical resonator

Chief Specialist: Prof.Gengyu Cao

Abstract:

    High sensitive detection of weak forces is of great importance in both fundamental study and applied science. Micro-mechanical resonators, which are used as universal forces transducers, have been the critical component of many sensing units. They have many applications in fundamental research and high precision measurements, such as Casimir force measurement, mechanical detection of single nuclear spins, and verification of the inverse square law. The measurement precision of mechanical resonator can be enhanced by suppressing its thermal oscillation through cooling. Although it's feasible to depress the thermal noise of the resonators through cooling to increase the measurement precision, there still exits the zero-point vibrational fluctuation even if cooling a resonator to its ground state, which sets the classical limit of mechanical-based force detection. As the rapid progress of high precision measurements towards the classical limit, it has become an emergent and challenging problem to perform measurement beyond the limit. Similar with achieving quantum measurement using the squeezed light, realizing of the mechanical squeezing affords a practical approach to beat the classical limit of mechanical-based force detection strategies. Benefiting from our knowledge and experiences on optical cooling and coherent manipulation of mechanical resonators, in this proposal, force detection beyond the classical limit will be investigated by integrating optical cooling and squeezing of mechanical oscillation in a fiber-based cavity-optomechanical system. The cavity enhanced optomechanical back-action would yield a stronger squeezing of mechanical oscillation, which provides a high potential route in realizing quantum
squeezing of mechanical resonator at room temperature and hence mechanical-based force detection beyond classical limit.