Tunable optomechanically induced transparency and fast-slow light in a loop-coupled optomechanical system

We theoretically explore the tunability of optomechanically induced transparency(OMIT)phenomenon and fast-slow light effect in a loop-coupled hybrid optomechanical system in which two optical modes are coupled to a common mechanical mode.In the probe output spectrum,we find that the interference phenomena OMIT caused by the optomechanical interactions and the normal mode splitting(NMS)induced by the strong tunnel coupling between the cavities can be observed.We further observe that the tunnel interaction will affect the distance and the heights of the sideband absorption peaks.The results also show that the switch from absorption to amplification can be realized by tuning the driving strength because of the existence of stability condition.Except from modulating the tunnel interaction,the conversion between slow light and fast light also can be achieved by adjusting the optomechanical interaction in the output field.This study may provide a potential application in the fields of high precision measurement and quantum information processing.

Optomechanically induced transparency with Bose Einstein condensate in double-cavity optomechanical system

We propose a novel technique of generating multiple optomechanically induced transparency （OMIT） of a weak probe field in hybrid optomechanical system. This system consists of a cigar-shaped Bose-Einstein condensate （BEC）, trapped inside each high finesse Fabry-P6rot cavity. In the resolved sideband regime, the analytic solutions of the absorption and the dispersion spectrum are given. The tunneling strength of the two resonators and the coupling parameters of the each BEC in combination with the cavity field have the appearance of three distinct OMIT windows in the absorption spectrum. Furthermore, whether there is BEC in each cavity is a key factor in the number of OMIT windows determination. The technique presented may have potential applications in quantum engineering and quantum information networks.

Phase-dependent double optomechanically induced transparency in a hybrid optomechanical cavity system with coherently mechanical driving

We propose a scheme that can generate tunable double optomechanically induced transparency in a hybrid optomechanical cavity system.In this system, the mechanical resonator of the optomechanical cavity is coupled with an additional mechanical resonator and the additional mechanical resonator can be driven by a weak external coherently mechanical driving field.We show that both the intensity and the phase of the external mechanical driving field can control the propagation of the probe field, including changing the transmission spectrum from double windows to a single-window.Our study also provides an effective way to generate intensity-controllable, narrow-bandwidth transmission spectra, with the probe field modulated from excessive opacity to remarkable amplification.

Controlling multiple optomechanically induced transparency in the distant cavity-optomechanical system

We theoretically investigate a two-cavity optomechanical system in which each optical cavity couples to a mechanical resonator via radiation pressure force,and the two optical cavities couple to each other via a distant waveguide.Our study shows that the multiple optomechanically induced transparency can be observed from the output field at the probe frequency.The number and width of the transparent windows can be tuned by the classical driving power Pl.We also analyze the distance of the two outermost transparency windows,which shows a linear relation with the parameters Pl andλ.Our approach is feasible for controlling multipartite induced transparency,which represents a valuable step towards quantum networks with photonic and phononic circuits.

Ideal optomechanically induced transparency generation in a cavity optoelectromechanical system

The ideal optomechanically induced transparency effects of an output probe field are investigated in a cavity optoelectromechanical system,which is composed of an optical cavity,a charged mechanical resonator,and a charged object.Although the charged mechanical resonator damping rate is nonzero,the ideal optomechanically induced transparency can still appear due to the non-rotating wave approximation effect in the system.The location of optomechanically induced transparency dip can be controlled via the Coulomb coupling strength.In addition,we find that both the transparency window width and the maximum dispersion curve slope are closely related to the optical cavity decay rate.

Excitations of optomechanically driven Bose Einstein condensates in a cavity: Photodetection measurements

We present a detailed study to analyze the Dicke quantum phase transition within the thermodynamic limit for an optomechanically driven Bose-Einstein condensate in a cavity. The photodetection-based quantum optical measurements have been performed to study the dynamics and excitations of this optomechanical Dicke system. For this, we discuss the eigenvalue analysis, fluorescence spectrum and the homodyne spectrum of the system. It has been shown that the normal phase is negligibly affected by the mechanical mode of the mirror while it has a significant effect in the superradiant phase. We have observed that the eigenvalues and the spectra both exhibit distinct features that can be identified with the photonic, atomic and phononic branches. In the fluorescence spectra, we further observe an asymmetric coherent energy exchange between the three degrees of freedom of the system in the superradiant phase arising as a result of optomechanical interaction and Bloch-Siegert shift.

Perfect optomechanically induced transparency in two-cavity optomechanics

Here,we study the controllable optical responses in a two-cavity optomechanical system,especially on the perfect optomechanically induced transparency(OMIT)in the model which has never been studied before.The results show that the perfect OMIT can still occur even with a large mechanical damping rate,and at the perfect transparency window the long-lived slow light can be achieved.In addition,we find that the conversion between the perfect OMIT and optomechanically induced absorption can be easily achieved just by adjusting the driving field strength of the second cavity.We believe that the results can be used to control optical transmission in modern optical networks.

Quantum correlations and entanglement in coupled optomechanical resonators with photon hopping via Gaussian interferometric power analysis

Quantum correlations that surpass entanglement are of great importance in the realms of quantum information processing and quantum computation.Essentially,for quantum systems prepared in pure states,it is difficult to differentiate between quantum entanglement and quantum correlation.Nonetheless,this indistinguishability is no longer holds for mixed states.To contribute to a better understanding of this differentiation,we have explored a simple model for both generating and measuring these quantum correlations.Our study concerns two macroscopic mechanical resonators placed in separate Fabry–Pérot cavities,coupled through the photon hopping process.this system offers a comprehensively way to investigate and quantify quantum correlations beyond entanglement between these mechanical modes.The key ingredient in analyzing quantum correlation in this system is the global covariance matrix.It forms the basis for computing two essential metrics:the logarithmic negativity(E_(N)^(m))and the Gaussian interferometric power(P_(G)^(m)).These metrics provide the tools to measure the degree of quantum entanglement and quantum correlations,respectively.Our study reveals that the Gaussian interferometric power(P_(G)^(m))proves to be a more suitable metric for characterizing quantum correlations among the mechanical modes in an optomechanical quantum system,particularly in scenarios featuring resilient photon hopping.

Nonlinearly induced entanglement in dissipatively coupled optomechanical system

Nonlinearly induced steady-state photon–phonon entanglement of a dissipative coupled system is studied in the bistable regime. Quantum dynamical characteristics are analysed by solving the mean-field and fluctuation equations of the system. It is shown that dissipative coupling can induce bistable behaviour for the effective dissipation of the system.Under suitable parameters, one of the steady states significantly reduces the dissipative effect of the system. Consequently,a larger steady-state entanglement can be achieved compared to linear dynamics. Furthermore, the experimental feasibility of the parameters is analysed. Our results provide a new perspective for the implementation of steady-state optomechanical entanglement.

Optomechanically induced non-reciprocity in the whispering gallery mode microresonator

With the support by the National Natural Science Foundation of China,Chinese Academy of Sciences,and Ministry of Science and Technology of China,the research group led by Dr.Dong Chunhua(董春华)at the CAS Key Lab of Quantum Information,University of Science and Technology of China。

Terahertz phononic crystal in plasmonic nanocavity

Interaction between photons and phonons in cavity optomechanical systems provides a new toolbox for quantum information technologies.A GaAs/AlAs pillar multi-optical mode microcavity optomechanical structure can obtain phonons with ultra-high frequency(~THz).However,the optical field cannot be effectively restricted when the diameter of the GaAs/AlAs pillar microcavity decreases below the diffraction limit of light.Here,we design a system that combines Ag nanocav-ity with GaAs/AlAs phononic superlattices,where phonons with the frequency of 4.2 THz can be confined in a pillar with~4 nm diameter.The Q_(c)/V reaches 0.22 nm^(-3),which is~80 times that of the photonic crystal(PhC)nanobeam and~100 times that of the hybrid point-defect PhC bowtie plasmonic nanocavity,where Q_(c) is optical quality factor and V is mode volume.The optome-chanical single-photon coupling strength can reach 12 MHz,which is an order of magnitude larger than that of the PhC nanobeam.In addition,the mechanical zero-point fluctuation amplitude is 85 fm and the efficient mass is 0.27 zg,which is much smaller than the PhC nanobeam.The phononic superlattice-Ag nanocavity optomechanical devices hold great potential for applications in the field of integrated quantum optomechanics,quantum information,and terahertz-light transducer.

Tunable phonon-atom interaction in a hybrid optomechanical system

We theoretically analyze a hybrid system consisting of a levitated neutral atom and a nanoparticle coupled to a cavity.The mechanical oscillator and the atom are effectively coupled to each other through the cavity photons as a bus.By adjusting the driving lasers,we can conveniently switch the phonon-atom coupling between Jaynes-Cummings(JC)and anti-JC forms,which can be used to manipulate the motional states of the mechanical oscillator.As an application,we prepare a superposition state of the mechanical oscillator via the effective phonon-atom interaction and investigate the effects of dissipation on the state generation.

Quantum properties of nonclassical states generated by an optomechanical system with catalytic quantum scissors

A scheme is proposed to investigate the non-classical states generated by a quantum scissors device(QSD) operating on the the cavity mode of an optomechanical system. When the catalytic QSD acts on the cavity mode of the optomechanical system, the resulting state contains only the vacuum, single-photon and two-photon states depending upon the coupling parameter of the optomechanical system as well as the transmission coefficients of beam splitters(BSs). Especially, the output state is just a class of multicomponent cat state truncations at time t = 2π by choosing the appropriate value of coupling parameter. We discuss the success probability of such a state and the fidelity between the output state and input state via QSD. Then the linear entropy is used to investigate the entanglement between the two subsystems, finding that QSD operation can enhance their entanglement degree. Furthermore, we also derive the analytical expression of the Wigner function(WF) for the cavity mode via QSD and numerically analyze the WF distribution in phase space at time t =2π. These results show that the high non-classicality of output state can always be achieved by modulating the coupling parameter of the optomechanical system as well as the transmittance of BSs.

Enhancement of the group delay in quadratic coupling optomechanical systems subjected to an external force

We theoretically study the effect of the quadratic coupling strength on optomechanical systems subjected to a continuous external force. Quadratic coupling strength originates from strong coupling between the optical and the mechanical degrees of freedom. We show that the quadratic coupling strength reduces the amplitude of the dispersion spectra at the resonance in both blue-and red-sideband regimes. However, it increases(decreases) the amplitude of the absorption spectrum in the blue-(red-)sideband regime. Furthermore, in both sideband regimes, the effective detuning between the pump and the cavity deviates with the quadratic coupling strength. Thereby, appropriate selection of the quadratic coupling strength results in an important magnification(in absolute value) of the group delay for both slow and fast light exiting from the optomechanical cavity.

Quantum estimation of rotational speed in optomechanics

We study the quantum Fisher information(QFI)of the angular velocity of rotation in an optomechanical system.Based on the Gaussian measurements method,we derive the explicit form of a single-mode Gaussian QFI,which is valid for arbitrary angular velocity of rotation.The information about the angular velocity to be measured is contained in the optical covariance matrix,which can be experimentally determined via homodyne measurement.We find that QFI increases rapidly when driving the system close to the unstable boundary.This result can be attributed to the strong nonlinearity of the system at the unstable boundary.Our results indicate the possibility of using an optomechanical system for high precision detection of the angular velocity of rotation.

Multi-window transparency and fast–slow light switching in a quadratically coupled optomechanical system assisted with three-level atoms

We study theoretically the features of the output field of a quadratically coupled optomechanical system assisted with three-level atoms. In this system, the atoms interact with the cavity field and are driven by a classical field, and the cavity is driven by a strong coupling field and a weak signal field. We find that there exists a multi-window transparency phenomenon. The width of the transparent windows can be adjusted by controlling the system parameters, including the number of the atoms, the powers of the lasers driving the atoms and driving the cavity, and the environment temperature. We also find that a tunable switch from fast light to slow light can be realized in this system.

Compound-induced transparency in three-cavity coupled structure

We propose a three-cavity coupled cavity optomechanical(COM)structure with tunable system parameters and theoretically investigate the probe-light transmission rate.Numerical calculation of the system’s spectra demonstrates distinctive compound-induced transparency(CIT)characteristics,including multiple transparency windows and sideband dips,which can be explained by a coupling between optomechanically-induced transparency(OMIT)and electromagnetically-induced transparency.The effects of optical loss(gain)in the cavity,number and topology of active cavity,tunneling ratio,and pump laser power on the CIT spectrum are evaluated and analyzed.Moreover,the optical group delay of CIT is highly controllable and fast–slow light inter-transition can be achieved.The proposed structure makes possible the advantageous tuning freedom and provides a potential platform for controlling light propagation and fast–slow light switching.

Review of cavity optomechanical cooling

Quantum manipulation of macroscopic mechanical systems is of great interest in both fundamental physics and ap- plications ranging from high-precision metrology to quantum information processing. For these purposes, a crucial step is to cool the mechanical system to its quantum ground state. In this review, we focus on the cavity optomechanical cooling, which exploits the cavity enhanced interaction between optical field and mechanical motion to reduce the thermal noise. Recent remarkable theoretical and experimental efforts in this field have taken a major step forward in preparing the mo- tional quantum ground state of mesoscopic mechanical systems. This review first describes the quantum theory of cavity optomechanical cooling, including quantum noise approach and covariance approach; then, the up-to-date experimental progresses are introduced. Finally, new cooling approaches are discussed along the directions of cooling in the strong coupling regime and cooling beyond the resolved sideband limit.

The optical nonreciprocal response based on a four-mode optomechanical system

We propose a scheme for realizing the optical nonreciprocal response based a four-mode optomechanical system,consisting of two charged mechanical modes and two linearly coupled optical modes. Two charged mechanical modes are coupled by Coulomb interaction, and two optical modes are coupled to one of mechanical modes by radiation pressure. We numerically evaluate the transmission probability of the probe field to obtain the optimum optical nonreciprocal response parameters. Also, we show that the optical nonreciprocal response is caused by the quantum interference between the optomechanical couplings and the linearly coupled interaction that breaks the time-reversal symmetry.

Tunable ponderomotive squeezing induced by Coulomb interaction in an optomechanical system

We investigate the properties of the ponderomotive squeezing in an optomechanical system coupled to a charged nanomecbanical oscillator （NMO） nearby via Coulomb force. We find that the introduction of Coulomb interaction allows the generation of squeezed output light from this system. Our numerical results show that the degree of squeezing can be tuned by the Coulomb coupling strength, the power of laser, and the frequencies of NMOs. Furthermore, the squeezing generated in our approach can be used to measure the Coulomb coupling strength.