Enhancing force sensing in a squeezed optomechanical system with quantum nondemolition measurement

A theoretical scheme is proposed to enhance the sensitivity of force sensors with quantum nondemolition 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.

Dynamical switchable quantum nonreciprocity induced by off-resonant chiral two-photon driving

Optical nonreciprocity,which refers to the direction-dependent emission,scattering and absorption of photons,plays a very important role in quantum engineering and quantum information processing.Here,we propose an all-optical approach to achieve the optical dynamical switchable quantum nonreciprocity by an off-resonant chiral two-photon driving in a single microring cavity,which differs from the conventional nonreciprocal schemes.It is shown that the optical field with time-dependent statistical properties can be generated and the nonreciprocity flips periodically,with switchable photon blockade and photon-induced tunneling effects.We find that the dynamical system is robust and immune to the parameter variations,which loosens the parameter range of system.Meanwhile,the time window for one-way quantum information is sufficiently wide and tunable.Our work opens a new idea for the current quantum nonreciprocal research,which can facilitate a memory functionality and be used for future inmemory superconducting quantum compute.The other nonreciprocal quantum devices,i.e.,dynamical switchable nonreciprocal squeezing and entanglement,may be inspired by our method,which is expected to have important applications in future quantum technology.

Strong mechanical squeezing in an optomechanical system based on Lyapunov control

We propose a scheme to generate strong squeezing of a mechanical oscillator in an optomechanical system through Lyapunov control.Frequency modulation of the mechanical oscillator is designed via Lyapunov control.We show that the momentum variance of the mechanical oscillator decreases with time evolution in a weak coupling case.As a result,strong mechanical squeezing is realized quickly(beyond 3 d B).In addition,the proposal is immune to cavity decay.Moreover,we show that the obtained squeezing can be detected via an ancillary cavity mode with homodyne detection.