Tunable Multiple Optomechanically Induced Transparency with Squeezed Fields in an Optomechanical System

A tunable multiple windows optomechanically induced transparency (OMIT) with a squeezed field is investigated in a system consisting of an optomechanical cavity coupled to a charged nanomechanical resonator (NAMR) via Coulomb interaction. Such a multiple OMIT can be achieved by adjusting the frequency of the charged NAMR and can be observed even with a single-photon squeezed field. In addition, this multiple OMIT for the quantized fields can be robust against cavity decay and environmental temperature. Specifically, the model under our consideration might be applied to precision measurement the frequency difference of two NAMRs within the reach of current techniques.     

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.     

Enhancing optomechanical force sensing via precooling and quantum noise cancellation

We theoretically investigate optomechanical force sensing via precooling and quantum noise cancellation in two coupled cavity optomechanical systems.We show that force sensing based on the reduction of noise can be used to dramatically enhance the force sensing and that the precooling process can eifectively improve the quantum noise cancellation.Specifically,we examine the effect of optomechanical cooling and noise reduction on the spectral density of the noise of the force measurement;these processes can significantly enhance the performance of optomechanical force sensing,and setting up the system in the resolved sideband regime can lead to an optimization of the cooling processes in a hybrid system.Such a scheme serves as a promising platform for quantum back-action-evading measurements of the motion and a framework for an optomechanical force sensor.     

回音壁微腔光力系统的相干控制与完全相干透射

本文研究了两侧同时输入的回音壁模谐振双微腔光力系统中电磁诱导透明的相干调控.通过改变双微腔两侧探测场的强度比值及相位差,可以有效控制电磁诱导透明窗口的宽度和深度,对探测场的吸收和色散等性质实施显著的影响,并且能够在特殊频率处产生关于探测场的完全相干透射现象.     

双光力诱导透明窗口的可调特性

提出一个杂化腔光力系统理论方案,利用两纳米机械振子间的库仑耦合作用实现弱探测光的双光力诱导透明窗口.研究边带可分辨区域和红失谐情况下双光力诱导透明窗口的可调特性.数值计算表明:两纳米振子间的库仑作用可有效地使单光力诱导透明窗口劈裂为双透明窗口.随着库仑耦合强度的增大,两透明窗口间的距离对称性地拉大;其次,光力腔衰减率的改变对两透明窗口的位置和深度无影响,仅对两透明窗口的宽度产生细微改变,测量精度可在坏腔情形下得到很好的保持;另外,仅增加参量放大器的非线性增益参量将使两透明窗口变宽,而引入驱动参量放大器的光场相位,利用相位匹配可以产生比空腔情形更加狭窄陡峭的双透明窗口,可用于比空腔情况更加精密的测量.     

Adjustable quantum coherence effects in a hybrid optomechanical system

We propose a system for achieving some adjustable quantum coherence effects, including the normal-mode splitting(NMS), the optomechanically induced transparency(OMIT), and the optomechanically induced absorption(OMIA). In this system, two tunnel-coupled optomechanical cavities are each driven by a coupling field and coupled to an atomic ensemble.Besides, one of the cavities is also injected with a probe field. When the system works under different conditions, we can obtain the NMS, the OMIT, and the OMIA, respectively. These effects can be flexibly adjusted by the tunnel coupling between the two cavities, the power of the coupling lasers, and the coupling strength between the atomic ensembles and the cavity fields. Furthermore, we can realize the OMIT even if the oscillating mirrors have relatively larger decay rates.     

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.     

基于压缩光的量子精密测量

对任何物理量的测量都有一定的噪声, 经典测量所能达到的最小噪声一般称为散粒噪声, 对应着测量的标准量子极限. 利用压缩光可以突破标准量子极限, 从而提高测量精度. 本文介绍了压缩态光场用于突破标准量子极限的基本原理, 以及压缩态光场在相位测量、光学横向小位移及倾斜测量、磁场测量以及时钟同步等精密测量领域的应用和最新进展.     

Super-sensitivity measurement of tiny Doppler frequency shifts based on parametric amplification and squeezed vacuum state

The precision measurement of Doppler frequency shifts is of great significance for improving the precision of speed measurement. This paper proposes a precision measurement scheme of tiny Doppler shifts by a parametric amplification process and squeezed vacuum state. This scheme takes a parametric amplification process and squeezed vacuum state into a detection system, so that the measurement precision of tiny Doppler shifts can exceed the Cram′er–Rao bound of coherent light. Simultaneously, a simulation study is carried out on the theoretical basis, and the following results are obtained: for the signal light of Gaussian mode, when the amplification factor g = 1 and the squeezed factor r = 0.5, the measurement error of Doppler frequency shifts is 14.4% of the Cramer–Rao bound of the coherent light in our system. At the same time,when the local light mode and squeezed vacuum state mode are optimized, the measurement precision of this scheme can be further improved by ■ times, where n is the mode-order of the signal light.     

原子辅助光力系统中快慢光的量子调控

随着纳米科技以及半导体技术的迅猛发展,光力诱导透明、快慢光和光存储以及其他在光力系统中发现的量子光学和非线性光学效应成为人们目前研究的热点.本文将薄膜腔光力系统同被束缚在腔中的二能级冷原子系综相耦合,通过直接在薄膜振子上引入弱辅助驱动场来研究该原子辅助光力系统中原子和相位对量子相干性质及其快慢光的调控.经过分析发现,通过改变辅助驱动场的强度可直接实现对光力诱导透明窗口深度的调控,通过改变辅助场与探测场之间的相位差,可实现输出的探测场在"吸收"、"透明"和"增益"之间相互转换,进而对弱探测场进行动态调控实现光开关.与此同时,还发现系统的群延迟时间随相位差的改变呈周期性变化.通过调节相位差及原子数,不但可以改变群延迟时间,还可实现快慢光之间的相互转换.     

Quantum effects of nonlinear spin waves in ferromagnets

We investigate a squeezed thermal spin state of nonlinear spin waves in Heisenberg ferromagnets. In this state, the magnon system possesses a new kind of quasiparticle, the dressed magnon, whose mass is a monotonically decreasing function of temperature. The noise of one spin component in the squeezed thermal spin state can be below the noise level in the vacuum state. The magnon system undergoes a first-order phase transition from the normal state to the squeezed thermal spin state. The critical temperature is much lower than the Curie temperature. A possible detection scheme based on a polarized neutron-scattering technique is suggested.     

Observation of electromagnetically induced transparency in a ring cavity

A scheme to observe Electromagnetically induced transparency (EIT) in an optomechanical system is proposed in the current paper. We treat a narrowband squeezed field as the weak probe field. We find that EIT dips exist in the output field. Moreover, the dependence of the EIT dips on the effective cavity detuning Δ and the input power ζ are explored. We show that the width of the EIT dips can be controlled by the parameters ξ and the detuning Δ.     

Suppressing laser phase noise in an optomechanical system

We propose a scheme to suppress the laser phase noise without increasing the optomechanical single-photon coupling strength.In the scheme,the parametric amplification terms,created by Kerr and Duffing nonlinearities,can restrain laser phase noise and strengthen the effective optomechanical coupling,respectively.Interestingly,decreasing laser phase noise leads to increasing thermal noise,which is inhibited by bringing in a broadband-squeezed vacuum environment.To reflect the superiority of the scheme,we simulate quantum memory and stationary optomechanical entanglement as examples,and the corresponding numerical results demonstrate that the laser phase noise is extremely suppressed.Our method can pave the way for studying other quantum phenomena.     

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.     

Entangled squeezed states:Bell state measurement and teleportation

We construct orthogonal Bell states with entangled squeezed vacuum states and show that these states can be discriminated with arbitrary precision when the amplitude of the squeezed states becomes sufficiently large. A scheme of teleporting a superposition state of the squeezed vacuum states based on the Bell state measurement is presented.     

Generation of squeezed vacuum on cesium D2 line down to kilohertz range

We report the experimental generation of a squeezed vacuum at frequencies ranging from 2.5 kHz to 200 kHz that is resonant on the cesium D2 line by using a below-threshold optical parametric oscillator(OPO). The OPO is based on a periodically-poled KTiOPO_4(PPKTP) crystal that is pumped using a bow-tie four-mirror ring frequency doubler. The phase of the squeezed light is controlled using a quantum noise locking technique. At a pump power of 115 mW, maximum quadrature phase squeezing of 3.5 d B and anti-squeezing of 7.5 d B are detected using a home-made balanced homodyne detector. This squeezed vacuum at an atomic transition in the kilohertz range is an ideal quantum source for quantum metrology of enhancing measurement precision, especially for ultra-sensitive measurement of weak magnetic fields when using a Cs atomic magnetometer in the audio frequency range.     

Interconversion of photon-phonon in a silica optomechanical microresonator

In an optomechanical resonator, the optical and mechanical excitations can be coherently converted, which induces a transparency window for a weak probe laser beam. Here, we report an experimental study of transient optomechanically induced transparency(OMIT) using the silica microsphere with the breathing modes. The transient OMIT behavior obtained are in good agreement with theoretical calculations. In addition, the coherent interconversion between optical and mechanical excitations that can be used for light storage and readout has also been studied here. Our experimental results indicate that the light storage is closely related to the process of OMIT, and the photon-phonon conversion can be further applied to optical wavelength or optical mode conversion.     

Generating a Squeezed‐Coherent‐Cat State in a Double‐Cavity Optomechanical System

A squeezed‐coherent‐cat state (SCCS) in a mechanical system not only plays an important role for macroscopic quantum coherence, but also can be a carrier for quantum information. A scheme to generate a SCCS in a two‐mode optomechanical system is proposed, in which the modulated hopping interaction of two cavities is introduced. The two cavity modes couple with the same mechanical mode with linear and quadratic interaction, respectively. The SCCS is analytically deduced under an appropriate initial state, and the average phonon number and the parameter of squeeze are numerically calculated. Wigner function shown the properties of superposition and squeezing is plotted. Including the dissipation of the environment, the results show that a high quality mechanical resonator and a low noise environment are required to obtain high fidelity.     

Triple optomechanical induced transparency in a two-cavity system

We theoretically investigate the optomechanical induced transparency(OMIT) phenomenon in a two-cavity system which is composed of two optomechanical cavities. Both of the cavities consist of a fixed mirror and a high-Q mechanical resonator, and they couple to each other via a common waveguide. We show that in the presence of a strong pump field applied to one cavity and a weak probe field applied to the other, a triple-OMIT can be observed in the output field at the probe frequency. The two mechanical resonators in the two cavities are identical, but they lead to different quantum interference pathways. The transparency windows are induced by the coupling of the two cavities and the optical pressure radiated to the mechanical resonators, which can be controlled via the power of the pump field and the coupling strength of the two cavities.     

Generating EPR-entangled mechanical state via feeding finite-bandwidth squeezed light

Einstein–Podolski–Rosen(EPR) entanglement state is achievable by combining two single-mode position and momentum squeezed states at a 50:50 beam-splitter(BS). We investigate the generation of the EPR entangled state of two vibrating membranes in a ring resonator, where clockwise(CW) and counter-clockwise(CCW) travelling-wave modes are driven by lasers and finite-bandwidth squeezed lights. Since the optomechanical coupling depends on the location of the membranes, CW and CCW can couple to the symmetric and antisymmetric combination of mechanical modes for a suitable arrangement, which corresponds to a 50:50 BS mixing. Moreover, by employing the red-detuned driving laser and tuning the central frequency of squeezing field blue detuned from the driving laser with a mechanical frequency, the squeezing property of squeezed light can be perfectly transferred to the mechanical motion in the weak coupling regime. Thus, the BS mixing modes can be position and momentum squeezed by feeding the appropriate squeezed lights respectively, and the EPR entangled mechanical state is obtained. Moreover, cavity-induced mechanical cooling can further suppress the influence of thermal noise on the entangled state.