Mass sensing by quantum criticality

Bogoliubov polaritons mediated strong indirect interaction between distant whispering-gallery-mode resonators

We propose a method to achieve a strong indirect interaction between two distant whispering-gallery-mode (WGM) resonators in a hybrid quantum system at room temperature, even when the distance between them exceeds 40 wavelengths. By exploiting the quantum critical point, we can greatly enhance both the effective damping rate and the coupling strengths between a WGM resonator and a low-frequency polariton. We introduce a large effective frequency detuning to suppress the effective damping rate while maintaining the enhanced coupling strength. The strong indirect interaction between separated WGM resonators is mediated by a far-off-resonant low-frequency polariton through virtual excitations in a process similar to Raman process. This proposal provides a viable approach to building a quantum network based on strongly coupled WGM resonators.

Cavity optomechanical chaos

Cavity optomechanics provides a powerful platform for observing many interesting classical and quantum nonlinear phenomena due to the radiation-pressure coupling between its optical and mechanical modes. In particular, the chaos induced by optomechanical nonlinearity has been of great concern because of its importance both in fundamental physics and potential applications ranging from secret information processing to optical communications. This review focuses on the chaotic dynamics in optomechanical systems. The basic theory of general nonlinear dynamics and the fundamental properties of chaos are introduced. Several nonlinear dynamical effects in optomechanical systems are demonstrated. Moreover, recent remarkable theoretical and experimental efforts in manipulating optomechanical chaotic motions are addressed. Future perspectives of chaos in hybrid systems are also discussed.

Ultra-high resolution mass sensing based on an optomechanical nonlinearity

Ultra-high resolution mass sensing used to be realized by measuring the changed mechanical oscillation frequency by a small mass that should be detected. In this work we present a different approach of mass sensing without directly measuring such mechanical frequency change but relying on the modified light field due to a previously less explored nonlinear mechanism of optomechanical interaction. The concerned optomechanical setup used for the mass sensing is driven by a sufficiently strong two-tone field satisfying a condition that the difference of these two drive frequencies matches the frequency of the mechanical oscillation, so that a nonlinear effect will come into being and lock the mechanical motion under the radiation pressure into a series of fixed orbits. A small mass attached to the mechanical resonator slightly changes the mechanical frequency, thus violating the exact frequency match condition. Such small change can be detected by the amplitude modification on the higher order sidebands of the cavity field. Even given a moderate mechanical quality factor for the setup, the added mass can still be detected to the levels corresponding to a mechanical frequency shift from 5 to 7 order less than the mechanical damping rate. Because the output cavity field difference for very close values of mechanical frequency is not blurred by thermal noise, such mass sensing can be well performed at room temperature. The previous tough requirements for ultra-high resolution mass sensing can be significantly relaxed by the method.

Force sensing in a dual-mode optomechanical system with linear-quadratic coupling and modulated photon hopping

A weak force sensor scheme is presented in an optomechanical system, in which the two cavity modes couple to a mechanical mode with linear and quadratic coupling. Due to introducing time-dependent hopping, the linear and quadratic coupling terms coexist under the rotating-wave approximation in the interaction picture. Compared with the quantum non-demolition measurement (ignoring the quadratic optomechanical coupling), the current scheme can decrease the additional noise to a lower level. Our proposal provides a promising platform for improving the detection of a weak force.