压缩真空场与耦合双原子Raman相互作用过程中光场的相位演化特性

采用Pegg-Barnett相位理论，研究了压缩真空场与耦合双原子Raman相互作用过程中光场的相位演化特性.具体计算了场的相位概率分布函数及相位涨落，给出了在极坐标中概率分布变化曲线.讨论了原子与场相互作用、两原子间偶极-偶极相互作用以及原子初始状态对光场相位性质的影响. 关键词： 相位特性 压缩真空场 耦合双原子 Raman相互作用     

双原子与单模腔场拉曼相互作用系统中光场相位统计性质

本文研究了双原子与单模光场拉曼相互作用系统中,在光场和原子具有不同的耦合并计及原子间衣一偶极相互作用情况下,光场相位的演化特性。给出了初始为极弱和极强相干态光场时光场相位概率分布,相位算符望值及相位涨落的解析表达式,并讨论了双原子与腔场之间耦合常数的相对大小原子偶极相互作用强度对辐射场相位统计性质的影响。     

双频场作用下三能级原子的动力学行为

求得双频场作用下串接型三能级原子系统哈密顿量的本征函数和本征值.从而给出任意初始原子态和任意偏调情况下,原子系统随时间的演化公式.研究了能级布居数和原子极化与光强的关系.揭示了原子初始条件和光场相对相位对原子动力学行为的影响.在相对相位为π时,原子场耦合最小,在特殊情况下为零.     

高Q克尔介质腔中依赖强度耦合的J-C模型中光场相位特性

应用Pegg-Barnett相位理论研究了被克尔介质包围的依赖强度耦合的J-C模型中光场相位演化特性, 结果发现, 原子-光场的耦合常数和克尔介质-光场的耦合常数将导致相位的涨落明显增大, 在原子初始处于非相干性激发时光场的频率也会发生漂移     

耦合场线宽和强度对双简并四能级系统的吸收和衍射效率的影响

采用密度矩阵方程,分别在引入耦合场线宽和强度、探测场频率变化以及耦合场频率与探测场频率之比变化的条件下,数值计算了双简并四能级原子系统中介质对探测场的吸收(增益)和相位光栅衍射效率的影响。结果表明:耦合场线宽的增大削弱了简并四能级原子相干;不考虑耦合场线宽(R=0)时的增益和衍射效率比考虑耦合场线宽(R≠0)时的大,在耦合光频率与探测光频率之比为ΩcΩp≈400时衍射效率最大可达到35%。     

非旋波耦合条件下微波控制的光学双稳与多稳

研究了在非旋波耦合条件下微波场建立的原子相干对光学双稳与多稳的控制.通过改变微波场的初始相位,可以有效地控制双稳与多稳的存在与否、迟滞环宽度和阈值强度的高低.旋波和非旋波耦合在物理上可视为双色激发,耦合的能级分裂成无穷多个子能级,原来的裸态跃迁变成无穷多个不同频率的跃迁.这些跃迁的相干叠加决定了介质的非线性吸收与色散,相干叠加的结果取决于微波场的相位. 关键词： 原子相干 非旋波耦合 光学双稳与多稳 相位控制     

非马尔可夫环境下原子的几何相位演化

从微观哈密顿量出发,研究了原子在非马尔可夫环境影响下的几何相位演化. 结果表明,在强耦合条件下原子的几何相位比弱耦合时获得的几何相位大, 而且这一差别随环境损耗的增加而增大. 在环境损耗较小时,原子的几何相位随时间变化出现连续和不连续两种演化行为,且不连续的范围随环境的损耗增加而增大. 总之,在非马尔可夫环境下,原子的几何相位演化将出现丰富而复杂的演化特征. 关键词： 几何相位 原子 腔场 非幺正     

原子与耦合腔相互作用系统中量子态保真度演化

在每个耦合腔中囚禁一个二能级原子并考虑原子与腔场的共振,研究二能级原子与耦合腔的相互作用.数值计算了耦合腔系统中系统、原子和腔场的保真度演化,讨论了腔场间耦合系数变化对保真度演化的影响.结果表明:随着腔场间耦合系数的增大,系统和原子的保真度从不规则振荡逐渐转变为准周期性振荡;腔场的保真度周期性变化;随腔场间耦合系数的增大,原子保真度降低,腔场的保真度增大.     

倒Y型四能级原子系统中电磁诱导透明的相干控制

研究了倒Y型四能级原子系统中相干控制电磁诱导透明.应用微扰理论给出一阶近似条件下,不同控制场原子系统对探测光场响应的解析式及电磁诱导透明窗宽度的解析式.在探测场为弱场时,分析了系统中控制光场强度、耦合光场强度及其失谐量对电磁诱导透明窗的影响.研究发现电磁诱导透明窗随控制光场强度的增强变宽,而随耦合光场强度的增强变窄,当探测光场与耦合光场偏离双光子共振时,透明窗外的吸收增加,透明窗变宽.在弱探测场、弱控制场条件下,分析了初始时刻原子处在相干叠加态时的相对相位、相对强度与探测场和控制场的相对相位等对系统吸收特性及透明窗的影响.结果表明探测场与控制场的相对相位对吸收的影响与相干叠加态中两能级之间几率幅的相对相位对吸收的影响作用相反,系统在两下能级干涉极大时,存在一个很宽的透明带.应用缀饰态理论和量子相干理论对所得结果进行了解释.     

相干原子束-相干腔场相互作用系统中量子信息的交换传递

利用演化因子给出了相干原子束与相干腔场相互作用系统的演化规律.研究了其相互作用过程,结果表明:量子信息不但可以在相干原子与相干腔场之间相互交换,而且可以在不同相干腔场之间传递.还发现:在普遍情况下,信息交换传递的条件与原子跃迁的频率(ωa,k)及其相对相位(ξ)、光场的频率(ωf,k)及其相对相位(η)、原子与光场的耦合强度(g)和相互作用时间(t)等均有关,但当原子与光场发生共振相互作用时,其条件仅与g、t有关.     

双光子过程耦合腔系统中光场的量子特性

本文研究了双光子过程原子与耦合腔相互作用系统中腔场的压缩效应和反聚束效应.考虑系统总激发数等于2的情况,利用数值计算方法讨论了腔场间的耦合强度变化和原子与腔场间耦合强度变化对反聚束效应的影响.研究结果表明:腔场不呈现出压缩效应;腔场的反聚束效应与原子与腔场的耦合系数之间,以及与腔场间的耦合系数之间都存在着非线性关系,     

Optomechanical dynamics in detuned whispering-gallery modes cavity

The dynamics of a microresonator in detuned whispering-gallery modes (WGM) cavity opto-mechanical system are investigated by the quantum Langevin equation. A WGM cavity coupling to two parallel waveguides is devised to study the transmission and reflection of this system. In single mode WGM cavity, without optomechanical coupling, both the transmission and reflection of the cavity present a Lorentzian dip and peak. When the coupling between the cavity mode and mechanical mode is considered, the transmission and reflection of the optomechanical cavity show “W” and “M” shape mode splitting. Moreover, under the action of a controlling and a probe laser, the output field at the probe frequency presents electromagnetically induced transparency (EIT)-like spectrum in the system. We give the physical origin of EIT-like and the pump-probe response for the WGM shares all the features of the Λ system in atoms. Further, due to backscattering, the two traveling waves in WGM are coupled with a rate γ. The transmission and reflection of the optomechanical cavity display three modes splitting in the spectra with optomechanical coupling between the two cavity modes and the mechanical mode.     

弱相干场耦合腔系统中的纠缠特性

研究由三个全同的二能级原子与耦合腔构成的系统, 考虑腔场处于弱相干态的情况. 采用Negativity熵度量两子系统间的纠缠, 利用数值计算方法研究了两个原子之间和两个腔场之间的纠缠性质. 讨论了腔场间的耦合系数和腔场的强度对纠缠特性的影响. 研究结果表明: 随光场强度增大, 原子间纠缠和腔场间纠缠均增强. 另一方面, 随耦合腔的耦合系数增大, 两原子间的纠缠减弱, 腔A和腔B间的纠缠增强; 而腔B和腔C间的纠缠, 以及腔A和腔C间纠缠与腔场间的耦合系数间存在非线性关系.     

Continuous-Variable Entanglement in a Coupled Field-Mesoscopic Josephson Junction System

Continuous-variable entanglement in the interacting system of a mesoscopic Josephson junction with a squeezed field is investigated. It is shown that when the cavity field is initially prepared in a squeezed vacuum state and the junction in its lowest energy state, the coupling system can evolve into a two-mode Caussian state. The timedependent characteristic function in the Wigner representation for the system is analytically obtained, and the squeezing degree of the initial cavity field turns out to have not only an apparent enhancing but also a weakening effect on the entanglement of the coupling system under suitable parameter conditions.     

Generation of maximally entangled atom pairs in driven dissipative cavity QED systems

We investigate the entanglement of an open tripartite system where a cavity field mode in thermal equilibrium is off-resonantly coupled with two atoms that are simultaneously driven by a resonant coherent field. For moderately detuned atom-field coupling and strong atomic driving we show the generation, at given interaction times and for low enough cavity decay rates, of atomic Bell states and of Bell state superpositions relevant for quantum gates implementation. The system can oscillate between bi-separable and fully separable states. Also we describe the distribution of quantum correlations between the atom-atom and the two atom-field subsystems. In the dispersive coupling regime with strongly driven atoms we show the generation of nearly stationary Bell states which remain protected from cavity dissipation.     

耦合双Tavis-Cummings模型中的纠缠演化和转移特性

研究了由光纤模连接的两个Tavis-Cummings模型中纠缠演化和纠缠转移的特性。结果表明,初始两原子间的纠缠可转移为另两原子间的纠缠,在纠缠转移过程中,光纤模起到中间传递的作用。纠缠的转移与初始两原子间的纠缠、原子与腔场的耦合强度以及光纤模与腔场的耦合强度、原子与腔场的失谐量和腔场耗散有关。初始纠缠决定了另两原子间纠缠产生的大小;在原子与腔场的耦合强度一定的条件下,随着光纤模与腔场耦合强度的增强,纠缠转移的时间缩短,且产生的纠缠值增加;腔场耗散对纠缠演化的衰减影响是显著的,而失谐量的增加可以有效地抑制这一现象。在整个纠缠转移过程中,系统中其他任两子体系间的纠缠起到了桥梁的作用,实现了两量子纠缠态的远程传递和制备。     

SOLUTION OF COUPLED ACOUSTIC PROBLEMS: A PARTIALLY OPENED CAVITY COUPLED WITH A MEMBRANE AND A SEMI-INFINITE EXTERIOR FIELD

There have been many attempts to understand the coupling phenomena between a solid structure and the surrounding fluid. However, the studies were restricted to interaction only between a structure and a finite cavity or a structure and acoustic field of infinite size. The system that we have studied has a structure that faces both a cavity of finite size and an external field of semi-infinite size. We also allow a hole, which can directly interact with the cavity as well as the external field. This configuration, therefore, provides two different interactions, or communication means. One is the finite structure and the other is the hole of finite size. This paper studies as to how these two components interact with the other two systems: the finite cavity covered by the structure and the hole, and the semi-infinite fluid. For simplicity, a two-dimensional and partially opened cavity coupled with a membrane and an exterior field was selected. The solution has to be found by solving a boundary value problem, but this case has to do with the boundaries that have two different conditions: one is the membrane and the other is the hole. The solution has been found in terms of the modal functions that satisfy the boundary conditions of finite cavity, membrane and hole. Non-dimensional coupling coefficients are obtained from the solution. The results exhibit that the coupling effect gives additional peaks and troughs in the averaged pressure of the cavity. These peaks and troughs are symmetrically arranged with respect to Helmholtz frequency of the cavity. The strong coupling occurs at the trough frequencies where the membrane interacts actively with the cavity and the exterior field.     

Berry phase in a generalized nonlinear two-level system

In this paper, we investigate the behaviour of the geometric phase of a more generalized nonlinear system composed of an effective two-level system interacting with a single-mode quantized cavity field. Both the field nonlinearity and the atom-field coupling nonlinearity are considered. We find that the geometric phase depends on whether the index k is an odd number or an even number in the resonant case. In addition, we also find that the geometric phase may be easily observed when the field nonlinearity is not considered. The fractional statistical phenomenon appears in this system if the strong nonlinear atom-field coupling is considered. We have also investigated the geometric phase of an effective two-level system interacting with a two-mode quantized cavity field.     

Berry phase in a generalized nonlinear two-level system

In this paper, we investigate the behaviour of the geometric phase of a more generalized nonlinear system composed of an effective two-level system interacting with a single-mode quantized cavity field. Both the field nonlinearity and the atom--field coupling nonlinearity are considered. We find that the geometric phase depends on whether the index $k$ is an odd number or an even number in the resonant case. In addition, we also find that the geometric phase may be easily observed when the field nonlinearity is not considered. The fractional statistical phenomenon appears in this system if the strong nonlinear atom--field coupling is considered. We have also investigated the geometric phase of an effective two-level system interacting with a two-mode quantized cavity field.     

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.