Nonreciprocal Mechanical Squeezing in a Spinning Optomechanical System

A scheme for nonreciprocal mechanical squeezing (NMS) based on the three‐mode optomechanical interaction is proposed. In this scheme, a mechanical mode couples to a spinning whispering‐gallery‐cavity (WGC) mode and to an optical mode. An external laser is coupled into and thus drives the WGC via a waveguide. Mechanical squeezing results from the joint effect of the mechanical intrinsic nonlinearity and the quadratic optomechanical coupling, which, in the presence of strong thermal noise, is still considerable, while the nonreciprocity originates from the optical Sagnac effect. There are two NMS areas in the parametric space, one works for the laser driving from the left of the waveguide and another, from the right. For a given spinning speed of the WGC, the squeezing values in these two areas are equal if the corresponding detunings of the WGC differ from each other by two‐times of the Sagnac–Fizeau shift. At the red‐detuning resonance, the analytical results for the mechanical squeezing and cooling are obtained. The NMS scheme is robust to the thermal noise of the mechanical environment.     

Perfect Optical Nonreciprocity with Mechanical Driving in a Three-Mode Optomechanical System *

Nonreciprocal devices are indispensable for building quantum networks and ubiquitous in modern communication technology. Here, we study perfect optical nonreciprocity in a three-mode optomechanical system with mechanical driving.The scheme relies on the interference between optomechanical interaction and mechanical driving. We find perfect optical nonreciprocity can be achieved even though nonreciprocal phase difference is zero if we drive the system by a mechanical driving with a nonzero phase. We obtain the essential conditions for perfectoptical nonreciprocity and analyze properties of the optical nonreciprocal transmission. These results can be used to control optical transmission in quantum information processing.      

双光腔耦合下机械振子的基态冷却

机械振子的基态冷却是腔量子光力学中的基本问题之一.所谓的基态冷却就是让机械振子的稳态声子数小于1.本文通过光压涨落谱和稳态声子数研究双光腔光力系统(标准单光腔光力系统中引入第二个光腔,并与第一个光腔直接耦合)的基态冷却.首先得到系统的有效哈密顿量,然后给出朗之万方程和速率方程,最后分别给出空腔和原子腔的光压涨落谱、冷却率和稳态声子数.通过光压涨落谱、冷却率和稳态声子数表达式,重点讨论空腔时机械振子的基态冷却,发现当满足最佳参数条件(机械振子的冷却跃迁速率对应光压涨落谱的最大值,而加热跃迁速率对应光压涨落谱的最小值)时,机械振子可以被冷却到稳态声子数足够少.此外分析:当辅助腔内注入原子系综时,若参数选择恰当可能更利于基态冷却.     

Spinning microresonator-induced chiral optical transmission

Chiral quantum optics is a new research area in light-matter interaction that depends on the direction of light propagation and offers a new path for the quantum regulation of light-matter interactions. In this paper, we study a spinning Kerr-type microresonator coupled with Λ-type atom ensembles, which are driven in opposite directions to generate asymmetric photon statistics. We find that a photon blockade can only be generated by driving the spinning resonator on right side without driving the spinning microresonator from the left side, resulting in chirality. The coupling strength between system modes can be precisely controlled by adjusting the detuning amount of the atomic pump field. Because of the splitting of the resonant frequency generated by the Fizeau drag, the destructive quantum interference generated in right side drive prevents the nonresonant transition path of state |1,0⟩ to state |2,0⟩. This direction-dependent chiral quantum optics is expected to be applied to chiral optical devices, single-photon sources and nonreciprocal quantum communications.     

Optomechanically Induced Mode Transition and Spectrum Enhancement in a Microresonator System

Optomechanics describes the interconnection between the terahertz optical field and mechanical microwave field, making it appealing in the context of nanophotonics and quantum information science. Here, the optomechanically induced mode transition and spectrum enhanced phenomenon in an optomechanical microcavity system are studied. An optical filter that is limited by the bandwidth of the mechanical mode is built. The analytical model is presented by considering a microresonator system which supports two electromagnetic modes and a single mechanical mode. Through the filtering of mechanical resonator, the optical spectral width becomes similar to the mechanical resonator bandwidth which can go beyond the limit of the cavity quality factor. It is found that the transition between the optomechanically induced transparency and the optomechanically induced absorption can be observed by tuning the coupling between the microresonator and the waveguide. Moreover, the controllable nonreciprocal excitation of the system can also be observed.     

Ground-state cooling based on a three-cavity optomechanical system in the unresolved-sideband regime

In the unresolved sideband regime,we propose a scheme for cooling mechanical resonator close to its ground state in a three-cavity optomechanical system,where the auxiliary cavities are indirectly connected with the mechanical resonator through standard optomechanical subsystem.The standard optomechanical subsystem is driven by a strong pump laser field.With the help of the auxiliary cavities,the heating process is suppressed and the cooling process of the mechanical resonator is enhanced.More importantly,the average phonon number is much less than 1 in a larger range.This means that the mechanical resonator can be cooled down to its ground state.All these interesting features will significantly promote the physical realization of quantum effects in multi-cavity optomechanical systems.     

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.     

Perfect optical nonreciprocity in a double-cavity optomechanical system

Nonreciprocal devices are indispensable for building quantum networks and ubiquitous in modern communication technology. Here, we propose to take advantage of the interference between optomechanical interaction and linearly-coupled interaction to realize optical nonreciprocal transmission in a double-cavity optomechanical system. Particularly, we have derived essential conditions for perfect optical nonreciprocity and analysed properties of the optical nonreciprocal transmission. These results can be used to control optical transmission in quantum information processing.     

Normal mode splitting and ground state cooling in a Fabry-Perot optical cavity and transmission line resonator

Optomechanical dynamics in two systems which are a transmission line resonator and Fabrya-Perot optical cavity via radiation-pressure are investigated by linearized quantum Langevin equation. We work in the resolved sideband regime where the oscillator resonance frequency exceeds the cavity linewidth. Normal mode splittings of the mechanical resonator as a pure result of the coupling interaction in the two optomechanical systems is studied, and we make a comparison of normal mode splitting of mechanical resonator between the two systems. In the optical cavity, the normal mode splitting of the movable mirror approaches the latest experiment very well. In addition, an approximation scheme is introduced to demonstrate the ground state cooling, and we make a comparison of cooling between the two systems dominated by two key factors, which are the initial bath temperature and the mechanical quality factor. Since both the normal mode splitting and cooling require working in the resolved sideband regime, whether the normal mode splitting influences the cooling of the mirror is considered. Considering the size of the mechanical resonator and precooling the system, the mechanical resonator in the transmission line resonator system is easier to achieve the ground state cooling than in optical cavity.     

Suppression of Stokes heating processes and improved optomechanical cooling with frequency modulation

Ground-state cooling of mesoscopic mechanical objects is still a major challenge in the unresolved-sideband regime. We present a frequency modulation (FM) scheme to achieve cooling of the mechanical resonator to its ground-state in a double-cavity optomechanical system containing a mechanical resonator. The mean phonon number is determined by numerically solving a set of differential equations derived from the quantum master equations. Due to efficient suppression of Stokes heating processes in the presence of FM, the ground-state cooling, indicated by numerical calculations, is significantly achievable, regardless of whether in the resolved-sideband regime or the unresolved-sideband regime. Furthermore, by choosing parameters reasonably, the improvement of the quantum cooling limit is found to be capable of being positively correlated with the modulation frequency. This method provides new insight into quantum manipulation and creates more possibilities for applications of quantum devices.     

High-sensitivity optical monitoring of a micromechanical resonator with a quantum-limited optomechanical sensor

We experimentally demonstrate the high-sensitivity optical monitoring of a micromechanical resonator and its cooling by active control. Coating a low-loss mirror upon the resonator, we have built an optomechanical sensor based on a very high-finesse cavity (30 000). We have measured the thermal noise of the resonator with a quantum-limited sensitivity at the 10(-19) m/sqrt[Hz] level, and cooled the resonator down to 5 K by a cold-damping technique. Applications of our setup range from quantum optics experiments to the experimental demonstration of the quantum ground state of a macroscopic mechanical resonator.     

High-Speed Quantum Transducer with a Single-Photon Emitter in a 2D Resonator

Quantum transducers can transfer quantum information between different systems. Microwave–optical photon conversion is important for future quantum networks to interconnect remote superconducting quantum computers with optical fibers. Here, a high-speed quantum transducer based on a single-photon emitter in an atomically thin membrane resonator, that can couple single microwave photons to single optical photons, is proposed. The 2D resonator is a freestanding van der Waals heterostructure (which may consist of hexagonal boron nitride, graphene, or other 2D materials) that hosts a quantum emitter. The mechanical vibration (phonon) of the 2D resonator interacts with optical photons by shifting the optical transition frequency of the single-photon emitter with strain or the Stark effect. The mechanical vibration couples to microwave photons by shifting the resonant frequency of an LC circuit that includes the membrane. Thanks to the small mass of the 2D resonator, both the single-photon optomechanical coupling strength and the electromechanical coupling strength can reach the strong coupling regime. This provides a way for high-speed quantum state transfer between a microwave photon, a phonon, and an optical photon.     

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.     

Optomechanical coupling between two optical cavities: Cooling of a micro-mirror and parametric normal mode splitting

We propose a technique aimed at cooling a harmonically oscillating mirror mechanically coupled to another vibrating mirror to its quantum mechanical ground state. Our method involves optomechanical coupling between two optical cavities. We show that the cooling can be controlled by the mechanical coupling strength between the two movable mirrors, the phase difference between the mechanical modes of the two oscillating mirrors and the photon number in each cavity. We also show that both mechanical and optical cooling can be achieved by transferring energy from one cavity to the other. We also analyze the occurrence of normal-mode splitting (NMS). We find that a hybridization of the two oscillating mirrors with the fluctuations of the two driving optical fields occurs and leads to a splitting of the mechanical and optical fluctuation spectra.     

Nonlocal nonreciprocal optomechanical circulator

A nonlocal circulator protocol is proposed in a hybrid optomechanical system. By analogy with quantum communication, using the input-output relationship, we establish the quantum channel between two optical modes with long-range. The three-body nonlocal interaction between the cavity and the two oscillators is obtained by eliminating the optomechanical cavity mode and verifying the Bell-CHSH inequality of continuous variables. By introducing the phase accumulation between cyclic interactions, the unidirectional transmission of quantum state between the optical mode and two mechanical modes is achieved. The results show that nonreciprocal transmissions are achieved as long as the accumulated phase reaches a certain value. In addition, the effective interaction parameters in our system are amplified, which reduces the difficulty of the implementation of our protocol. Our research can provide potential applications for nonlocal manipulation and transmission control of quantum platforms.     

Effective mass in quantum effects of radiation pressure

We study the quantum effects of radiation pressure in a high-finesse cavity with a mirror coated on a mechanical resonator. We show that the optomechanical coupling can be described by an effective susceptibility which takes into account every acoustic modes of the resonator and their coupling to the light. At low frequency this effective response is similar to a harmonic response with an effective mass smaller than the total mass of the mirror. For a plano-convex resonator the effective mass is related to the light spot size and becomes very small for small optical waists, thus enhancing the quantum effects of optomechanical coupling.     

Weak-force sensing with squeezed optomechanics

We investigate quantum-squeezing-enhanced weak-force sensing via a nonlinear optomechanical resonator containing a movable mechanical mirror and an optical parametric amplifier(OPA). Herein, we determined that tuning the OPA parameters can considerably suppress quantum noise and substantially enhance force sensitivity, enabling the device to extensively surpass the standard quantum limit. This indicates that under realistic experimental conditions, we can achieve ultrahigh-precision quantum force sensing by harnessing nonlinear optomechanical devices.     

Starspots,stellar cycles and stellar flares: Lessons from solar dynamo models

We theoretically investigate the multistable behavior of a hybrid optomechanical system,in which a charged mechanical resonator is coupled via Coulomb interaction to an optomechanical cavity containing an optical parametric amplifier(OPA).It is shown that the multistable behavior of the mean intracavity photon number can be controlled flexibly by adjusting the nonlinear gain parameter of the OPA,the phase of the field pumping the OPA,the power and frequency of the field driving the cavity,and the Coulomb coupling strength between the two charged mechanical resonators.In particular,the increase of the nonlinear gain parameter can result in a transition from testability to Instability.Moreover,the effect of the Coulomb coupling strength on the bistable behavior of the steady-state positions of the two mechanical resonators is discussed.     

Irreversibility in an Optical Parametric Driven Optomechanical System

This study investigates the role of nonlinearity via optical parametric oscillator on the entropy production rate and quantum correlations in a hybrid optomechanical system. Specifically, the modified entropy production rate of an optical parametric oscillator placed in the optomechanical cavity is derived, which is well described by the two-mode Gaussian state. The irreversibility and quantum mutual information associated with the driving the system far from equilibrium are found to be controlled by the phase and strength of nonlinearity. This analysis shows that the system entropy flow, heating, or cooling, are determined by choosing the appropriate phase of the self-induced nonlinearity. It is further demonstrated that this effect persists for a reasonable range of cavity decay rate.     

双腔光力学系统中输出光场纠缠特性的研究

腔光力学系统中的光辐射压力可以使系统中的各个子系统之间产生量子纠缠,最近在腔光力学系统中的量子纠缠引起了人们广泛的关注.本文研究了双腔光力系统中关于输出光场之间纠缠的性质,发现:此系统中力学振子的弛豫速率和滤波器带宽以及非相等耦合对输出光场之间纠缠的大小有着非常显著的影响,特别是在相等耦合条件下,输出光场中心频率与光腔本征频率近共振时,滤波器带宽对输出光场纠缠有着显著的抑制作用;但是如果采用非相等耦合,则可以有效抵制滤波器带宽对纠缠的抑制作用,使输出光场纠缠得到大幅提高.研究结果可应用在光力耦合系统中实现量子态转换、量子隐形传态等量子信息处理过程.