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.

Nonreciprocal generation of Schrodinger cat state induced by topology

The Schrodinger cat state produced differently in two directions is anticipated to be a critical quantum resource in quantum information technologies.By exploring the interplay between quantum nonreciprocity and topology in a one-dimensional microcavity array,we obtain the Schrodinger cat state(a pure quantum state)in a chosen direction at the edge cavity,whereas a classical state in the other direction.This nonreciprocal generation of the cat state originates from the topologically protected chiralitymode excitation in the nontrivial phase,but in the trivial phase,the nonreciprocal generation of cat state vanishes.Thus,our proposal is switchable by tuning the parameters so that a topological phase transition occurs.Moreover,the obtained cat state has nonreciprocal high fidelity,nonclassicality,and quantum coherence,which are sufficient to be used in various one-way quantum technologies,e.g.,invisible quantum sensing,noise-tolerant quantum computing,and chiral quantum networks.Our work provides a general approach to control quantum nonreciprocities with the topological effect,which substantially broadens the fields of nonreciprocal photonics and topological physics.

Collective radiance of giant atoms in non-Markovian regime

We investigate the non-Markovian dynamics of two giant artificial atoms interacting with a continuum of bosonic modes in a onedimensional(1D) waveguide.Based on the diagrammatic method,we present the exact analytical solutions,which predict the rich phenomena of collective radiance.For the certain collective states,the decay rates are found to be far beyond that predicted in the the Dicke model and standard Markovian framework,which indicates the occurrence of super-superradiance.The superadiance-to-subradiance transition could be realized by adjusting the exchange symmetry of giant atoms.Moreover,there exist multiple bound states in continuum(BICs),with photons/phonons bouncing back and forth in the cavity-like geometries formed by the coupling points.The trapped photons/phonons in the BICs can also be re-released conveniently by changing the energy level splitting of giant atoms.The mechanism relies on the joint effects of the coherent time-delayed feedback and the interference between the coupling points of giant atoms.This work fundamentally broadens the fields of giant atom collective radiance by introducing non-Markovianity.It also paves the way for a clean analytical description of the nonlinear open quantum system with more complex retardation.

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.

Synergistic enhancement of spin-phonon interaction in a hybrid system

An investigation to significantly enhance coupling to nitrogen-vacancy(NV)centers at a single-quanta level is of great interest to further explore its applications in quantum information processing(QIP).This study explores a joint scheme to further enhance NV-phonon coherent coupling with two methods working together in hybrid optomechanical systems.Both methods are mechanics-induced mode field coupling(MFC)that lead,respectively,to the modification of the spatial distribution of the optical field and the mechanical parametric amplification(MPA)realized by modulating the mechanical spring constant in time.With the joint assistance of MFC and MPA,the coherent coupling between the NV spin and one supermode of the mechanical resonators(MRs)can be further significantly enhanced with the rate∝n_(cav)e^(r).Several potential applications are also discussed in this work.With the ultimate goal to enhance the coupling to NV spin at a single-quanta level,this attempt may provide a promising spin-phonon platform to implement more active control.