Cavity optomechanics with cold atomic gas

We present a tutorial review on the topics related to current development in cavity optomechanics, with special emphasis on cavity optomechanical effects with ultracold gases, Bose-Einstein condensates, and spinor Bose-Einstein condensates. Topics including the quantum model and nonlinearity of the cavity optomechanics, the principles of optomechanical cooling, radiation-pressure-induced nonlinear states, the chaotic dynamics in a condensate-mirror-hybrid optomechanical setup, and the spin-mixing dynamics controlled by optical cavities are covered.     

三机械薄膜腔光力系统相互作用的研究

本文主要研究了利用传输矩阵理论和共振透射条件详细地推导光腔中均匀放置三个机械薄膜构成的腔光力系统中系统本征模式随机械运动的色散关系.计算结果发现系统的光学本征模式由一组四个的本征能级构成,且不同的能级随不同的机械运动模式的变化曲线各不相同,进而导致不同光学模式与不同机械运动模式之间的耦合也不相同.此外,利用微扰理论求解了当机械运动振幅远小于腔模波长、机械振子处于平衡位置附近时,各种光学模式与不同机械振动模式间相互作用耦合强度的解析表达式.研究结果能够为理论和实验上研究多模腔光力系统提供一定的参考.     

Strong Coupling Optomechanics Mediated by a Qubit in the Dispersive Regime

Cavity optomechanics represents a flexible platform for the implementation of quantum technologies, useful in particular for the realization of quantum interfaces, quantum sensors and quantum information processing. However, the dispersive, radiation–pressure interaction between the mechanical and the electromagnetic modes is typically very weak, harnessing up to now the demonstration of interesting nonlinear dynamics and quantum control at the single photon level. It has already been shown both theoretically and experimentally that if the interaction is mediated by a Josephson circuit, one can have an effective dynamics corresponding to a huge enhancement of the single-photon optomechanical coupling. Here we analyze in detail this phenomenon in the general case when the cavity mode and the mechanical mode interact via an off-resonant qubit. Using a Schrieffer–Wolff approximation treatment, we determine the regime where this tripartite hybrid system behaves as an effective cavity optomechanical system in the strong coupling regime.     

Dissipative optomechanics in a Michelson-Sagnac interferometer

Dissipative optomechanics studies the coupling of the motion of an optical element to the decay rate of a cavity. We propose and theoretically explore a realization of this system in the optical domain, using a combined Michelson-Sagnac interferometer, which enables a strong and tunable dissipative coupling. Quantum interference in such a setup results in the suppression of the lower motional sideband, leading to strongly enhanced cooling in the non-sideband-resolved regime. With state-of-the-art parameters, ground-state cooling and low-power quantum-limited position transduction are both possible. The possibility of a strong, tunable dissipative coupling opens up a new route towards observation of such fundamental optomechanical effects as nonlinear dynamics. Beyond optomechanics, the suggested method can be readily transferred to other setups involving nonlinear media, atomic ensembles, or single atoms.     

Tunable cavity optomechanics with ultracold atoms

We present an atom-chip-based realization of quantum cavity optomechanics with cold atoms localized within a Fabry-Perot cavity. Effective subwavelength positioning of the atomic ensemble allows for tuning the linear and quadratic optomechanical coupling parameters, varying the sensitivity to the displacement and strain of a compressible gaseous medium. We observe effects of such tuning on cavity optical nonlinearity and optomechanical frequency shifts, providing their first characterization in the quadratic-coupling regime.     

参量放大器腔中光力诱导透明与本征模劈裂性质

研究了在含有光学参量放大器的光力学腔中关于弱探测光的光力诱导透明与本征模劈裂的性质.研究发现,光学参量放大器的驱动场相位和非线性增益值的大小对光力诱导透明窗口宽度和本征模劈裂性质有非常重要的影响,特别是当控制光频率工作在光力学红边带下,通过适当调制相位和非线性增益可以实现比空腔时(没有光学参量放大器时)还狭窄的光力诱导透明窗口,此时伴随着陡峭的色散曲线.这些研究结果有利于在光力耦合系统中实现快慢光、光存储等量子信息处理过程.     

Optomechanical sensing with on-chip microcavities

The coupling between optical and mechanical degrees of freedom has been of broad interest for a long time. However, it is only until recently, with the rapid development of optical mierocavity research, that we are able to manipulate and utilize this coupling process. When a high Q microeavity couples to a mechanical resonator, they can consolidate into an optomeehanieal system. Benefitting from the unique characteristics offered by optomeehanical coupling, this hybrid system has become a promising platform for ultrasensitive sensors to detect displacement, mass, force and acceleration. In this review, we introduce the basic physical concepts of cavity optomechanies, and describe some of the most typical experimental cavity optomechanical systems for sensing applications. Finally, we discuss the noise arising from various sources and show the potentiality of optomechanical sensing towards quantum-noise-limited detection.     

Cavity optomechanics: Manipulating photons and phonons towards the single-photon strong coupling

Cavity optomechanical systems provide powerful platforms to manipulate photons and phonons, open potential applications for modern optical communications and precise measurements. With the refrigeration and ground-state cooling technologies, studies of cavity optomechanics are making significant progress towards the quantum regime including nonclassical state preparation, quantum state tomography, quantum information processing, and future quantum internet. With further research, it is found that abundant physical phenomena and important applications in both classical and quantum regimes appeal as they have a strong optomechanical nonlinearity, which essentially depends on the single-photon optomechanical coupling strength. Thus, engineering the optomechanical interactions and improving the single-photon optomechanical coupling strength become very important subjects. In this article, we first review several mechanisms,theoretically proposed for enhancing optomechanical coupling. Then, we review the experimental progresses on enhancing optomechanical coupling by optimizing its structure and fabrication process. Finally, we review how to use novel structures and materials to enhance the optomechanical coupling strength. The manipulations of the photons and phonons at the level of strong optomechanical coupling are also summarized.     

On the Interaction of Massive Photons and Mechanical Oscillators in Cavity Optomechanics: Basic Model and Quantization

This study investigates the theoretical aspects of the interaction between photons with mass and a mechanical oscillator as drawn within the framework of cavity optomechanics. The study employs Proca theory as the mathematical framework to initially describe the dynamics of massive photons in a Fabry-Perot cavity with a movable mass, both in classical and quantum scenarios. It quantifies the modifications induced by the nonzero photon mass, considering first- and second-order effects, and derives expressions for the amplification of radiation pressure resulting from the presence of nonzero photon mass. Additionally, it derives the Hamiltonian of the quantum optomechanical system, incorporating the effects of photon mass at first and second order. It anticipates that experimental realization of massive optomechanics can be achieved by utilizing Proca material, which is a spatio-temporally dispersive material that exhibits behavior equivalent to Proca theory in a vacuum, thus enabling the study of the interaction between massive photons and mechanical systems in cavity-based optomechanical setups (referred to as massive cavity optomechanics). The study presented here caters to a diverse audience with an interest in the analysis and measurement of interactions among massive objects at the quantum scale.     

腔光力系统制备微波非经典态研究进展

腔光力系统作为一种新型的混合量子系统,因其超强耦合度、低温超导条件下极低的噪声、较长的相干时间等优势而成为被广受关注的量子实验平台.本文简要介绍腔光力学及腔光力系统基本原理,对常见腔光力系统进行分类,详细介绍利用广义腔光力系统进行微波非经典量子态制备的相关进展,对其性能优势和待解决问题进行分析,最后总结相关应用场景并对未来的潜在应用领域进行了展望.     

Photon blockade effect in optomechanical systems

We analyze the photon statistics of a weakly driven optomechanical system and discuss the effect of photon blockade under single-photon strong coupling conditions. We present an intuitive interpretation of this effect in terms of displaced oscillator states and derive analytic expressions for the cavity excitation spectrum and the two-photon correlation function g(2)(0). Our results predict the appearance of nonclassical photon correlations in the combined strong coupling and sideband resolved regime and provide a first detailed understanding of photon-photon interactions in strong coupling optomechanics.     

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.     

A short walk through quantum optomechanics

This paper gives a brief review of the basic physics of quantum optomechanics and provides an overview of some of its recent developments and current areas of focus. It first outlines the basic theory of cavity optomechanical cooling and gives a brief status report of the experimental state‐of‐the‐art. It then turns to the deep quantum regime of operation of optomechanical oscillators and covers selected aspects of quantum state preparation, control and characterization, including mechanical squeezing and pulsed optomechanics. This is followed by a discussion of the “bottom‐up” approach that exploits ultracold atomic samples instead of nanoscale systems. It concludes with an outlook that concentrates largely on the functionalization of quantum optomechanical systems and their promise in metrology applications.     

腔光力学系统中的量子测量

腔光力学系统近年来迅猛发展, 在精密测量、量子传感等方面已展现出重要的应用价值. 特别是与微纳技术和冷原子技术结合后, 这一系统正发展成为研究量子测量与量子操控的理想平台. 本文首先综述腔光力学在量子测量, 尤其是量子测量基础理论研究方面的进展; 然后分析腔光力学系统中的量子测量原理; 最后介绍我们近来在这方面的研究进展, 并通过我们设计的一系列新颖的基于腔光力学系统的量子测量方案来具体展示该系统在量子测量、量子操控等方面的潜在应用.     

Normal Mode Splitting in a Cavity Optomechanical System with a Cubic Anharmonic Oscillator

The strong coupling between a macroscopic mechanical oscillator and a cavity field is essential for many quantum phenomena in a cavity optomechanical system. In this work, we discuss the normal mode splitting in a cavity optomechanical system with a cubic nonlinear movable mirror. We study how the mechanical nonlinearity affects the normal-mode splitting behavior of the movable mirror and the output field. We find that the mechanical nonlinearity can increase the peak separation in the spectra of the movable mirror and the output field. We also find that the heights and linewidths of the two peaks are very sensitive to the mechanical nonlinearity.

     

Measuring orbital angular momentum of vortex beams in optomechanics

Measuring the orbital angular momentum (OAM) of vortex beams, including the magnitude and the sign, has great application prospects due to its theoretically unbounded and orthogonal modes. Here, the sign-distinguishable OAM measurement in optomechanics is proposed, which is achieved by monitoring the shift of the transmission spectrum of the probe field in a double Laguerre–Gaussian (LG) rotational-cavity system. Compared with the traditional single LG rotational cavity, an asymmetric optomechanically induced transparency window can occur in our system. Meanwhile, the position of the resonance valley has a strong correlation with the magnitude and sign of OAM. This originally comes from the fact that the effective detuning of the cavity mode from the driving field can vary with the magnitude and sign of OAM, which causes the spectral shift to be directional for different signs of OAM. Our scheme solves the shortcoming of the inability to distinguish the sign of OAM in optomechanics, and works well for high-order vortex beams with topological charge value±45, which is a significant improvement for measuring OAM based on the cavity optomechanical system.     

Optomechanical Dark State in a Dual-Species Bose-Einstein Condensate

We study cavity optomechanics of ultracold dual-species atomic mixtures with nonlinear collisions.Interspecies interactions provide a direct parametric coupling of fictitious mechanical elements which,through interfering with the intracavity optical field,leads to a switchable optically-dark state for either species.This demonstrates a matter-wave analog of recently observed mechanical wave mixing and quantum motional-state swapping,with applications in the construction of integrated phononic devices,and the cavity-enhanced detection of quantum degenerate atomic mixtures.     

Multiple induced transparency in a hybrid driven cavity optomechanical device with a two-level system

We present a scheme with the multiple-induced transparency windows in a hybrid optomechanical device. By studying the transmission of a probe field through the hybrid device, we show the successive generations of three transparent windows induced by multiple factors including tunneling, optomechanical and qubit-phonon coupling interactions, and analyze the physical mechanism of the induced transparency based on a simplified energy-level diagram of the system. Moreover, the effects of the transition frequency and decay rate of the two-level system on the multiple-induced transparency windows are discussed. We find that the transparency windows can be modulated by the coupling interaction between the qubit and NMR, the decay of qubit and the power of the control field. Therefore, the transmission of the probe field can be coherently adjusted in the hybrid cavity optomechanical device with a two-level system.     

Spectrum of Single-Photon Scattering in a Strong-Coupling Hybrid Optomechanical System

The single-photon excitation and transmission spectra of strong-coupling hybrid optomechanics are theoretically analyzed, where a two-level system (TLS) is coupled to a mechanical resonator (MR), generating Jaynes–Cummings-type polariton doublets. In this model, both the optomechanical coupling and the TLS-MR coupling are strong. In this parameter region, polaron-assisted excitation reemission processes can strongly affect the single-photon excitation and output spectra of the cavity. It is found that the fine structure around each sideband can be used to characterize the TLS-MR and the effective TLS-photon couplings, even at the single-quantum level. Thus, the spectrum structures may make it possible to sensitively probe the quantum nature of a macroscopic mechanical element. A possible approach for tomographic reconstruction of the state of a TLS, utilizing the single-photon transmission spectra, is further provided.     

Dynamics and entanglement of a membrane-in-the-middle optomechanical system in the extremely-large-amplitude regime

The study of optomechanical systems has attracted much attention, most of which are concentrated in the physics in the smallamplitude regime. While in this article, we focus on optomechanics in the extremely-large-amplitude regime and consider both classical and quantum dynamics. Firstly, we study classical dynamics in a membrane-in-the-middle optomechanical system in which a partially reflecting and flexible membrane is suspended inside an optical cavity. We show that the membrane can present self-sustained oscillations with limit cycles in the shape of sawtooth-edged ellipses and exhibit dynamical multistability. Then, we study the dynamics of the quantum fluctuations around the classical orbits. By using the logarithmic negativity, we calculate the evolution of the quantum entanglement between the optical cavity mode and the membrane during the mechanical oscillation. We show that there is some synchronism between the classical dynamical process and the evolution of the quantum entanglement.