非旋波近似下Λ型三能级原子与相干态光场的量子纠缠

在非旋波近似下,利用相干态正交化展开方法,对相干态光场与Λ型三能级原子相互作用的量子场熵进行了精确求解.利用量子熵理论讨论了耦合强度、平均光子数以及初始时刻原子处于不同的能级对量子纠缠的影响.数值计算的结果表明：当初始时刻原子处于激发态时,量子纠缠在较短的时间内就能演化到最大值,随着平均光子数的增大,纠缠演化的周期性逐渐明显|原子初始时刻处于三个能级的叠加态会使初始阶段量子纠缠显著降低|与旋波近似下的结果不同的是,随着耦合强度以及平均光子数的增加,非旋波项的贡献显著增强,使得量子纠缠演化曲线出现小锯齿状的振荡.     

非旋波近似下Λ型三能级原子与相干态光场的量子纠缠

在非旋波近似下,利用相干态正交化展开方法,对相干态光场与Λ型三能级原子相互作用的量子场熵进行了精确求解.利用量子熵理论讨论了耦合强度、平均光子数以及初始时刻原子处于不同的能级对量子纠缠的影响.数值计算的结果表明:当初始时刻原子处于激发态时,量子纠缠在较短的时间内就能演化到最大值,随着平均光子数的增大,纠缠演化的周期性逐渐明显;原子初始时刻处于三个能级的叠加态会使初始阶段量子纠缠显著降低;与旋波近似下的结果不同的是,随着耦合强度以及平均光子数的增加,非旋波项的贡献显著增强,使得量子纠缠演化曲线出现小锯齿状的振荡.     

V型三能级原子双模光场系统中的量子特性

研究了双模相干态光场与V型原子相互作用的量子系统,并在非旋波近似下对量子系统的布居概率和量子纠缠进行了精确求解。讨论了平均光子数■以及原子初始状态能级叠加对布局概率和量子纠缠的影响,分析了非旋波项跃迁对量子系统动力学特点产生影响的原因。结果表明:随着■的增大布居概率和量子纠缠演化周期逐渐增大。布居概率塌缩区对应系统纠缠度较小,布居概率回复区对应系统纠缠度较大。原子处于叠加态时,量子纠缠初始值和平均值会降低。非旋波项的跃迁使布居概率和纠缠演化曲线出现锯齿状振荡。     

非相干泵浦过程对光学双稳的影响

研究了低能级偶极子的非相干泵浦过程环形腔中双稳行为的影响，结果表明，耦合系统的双稳机制为非相干泵浦过程的干涉性，双稳迟滞环与非相干泵浦场有严格的对应关系，在一定条件下，甚至出现多稳态，可以利用非相干泵浦的干步性能控制光学双稳。     

薛定谔猫态光场与二能级原子相互作用系统的量子特性

在非旋波近似下,通过采用相干态正交化展开的方法,研究了薛定谔猫态光场与二能级原子相互作用系统中,原子的布局数和光场的反聚束效应,并与旋波近似下的结果进行了对比.在旋波近似与非旋波近似下,讨论了初始光场强度、相干态间的相位角以及失谐量对原子布局数和光场反聚束效应的影响;在非旋波近似下,讨论了强弱耦合情况下光场的反聚束效应.研究结果表明:旋波近似与非旋波近似下,原子的布局数随着初始光场强度的不同,表现出不同的特性;当初始光场强度较小时,旋波近似与非旋波近似下,原子的布局数表现出相同的特性;随着初始光场强度的增大,旋波近似下,原子的布局数将表现出坍塌现象.耦合强度较大时,光场的聚束与反聚束效应在非旋波近似与旋波近似下有较大的区别;非旋波近似下,随着初始光场强度的增大,光场一直处于聚束效应状态;而旋波近似下,光场的聚束效应与反聚束效应交替出现.     

微波场驱动下V型三能级原子的吸收和色散特性

当用微波场作用到V型三能级原子的两个激发态能级时,系统跃迁路径之间发生交叉耦合导致了量子相干效应.通过调节微波场的强度,可实现对原子吸收和色散性质的改变,并呈现零吸收高折射率现象.此外,微波场诱导的量子相干也可实现相对相位对探测光增益的控制.     

微波场驱动下V型三能级原子的吸收和色散特性

当用微波场作用到V型三能级原子的两个激发态能级时,系统跃迁路径之间发生交叉耦合导致了量子相干效应.通过调节微波场的强度,可实现对原子吸收和色散性质的改变,并呈现零吸收高折射率现象.此外,微波场诱导的量子相干也可实现相对相位对探测光增益的控制.     

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.     

非旋波近似下两纠缠原子的纠缠特性

采用了相干态正交化法研究了耦合强度以及偶极相互作用对Tavis-Cummings模型中两原子的纠缠的影响.与旋波近似比较发现,在弱耦合强度下,非旋波近似下两原子间的纠缠与旋波近似下的结果符合得很好,在强耦合区,原子之间的纠缠出现了突然死亡现象.研究同时发现耦合强度越大,原子间处于可分离态的时间越长,表明了原子间处于退纠缠的时间的长短是依赖于原子-光场的耦合强度的.而考虑了偶极相互作用时,随着偶极-偶极相互作用的加强,原子间的纠缠也将被加强.     

精确求解级联型三能级原子与单模相干态光场场熵的演化特性

本文利用全量子理论,在非旋波近似下对单模相干态光场与级联型三能级原子相互作用过程中场熵随时间的演化进行了精确求解.数值计算的结果表明：随着初始时刻平均光子数n以及光场与原子的耦合强度u, v的增大,场熵的平均值先增大后减小,因此纠缠度也同样先增大后减小;随着失谐量Δ的增大,场熵的平均值逐渐减小,因此纠缠度也逐渐减小. 关键词： 相干态正交化展开 非旋波近似 场熵     

Optical Bistability and Multistability in an EIT Medium with Two-Photon Resonance Transitions

Intensity threshold of optical bistability (OB) and optical multistability (OM) can be controlled by amplitude and phase control of microwave driven field in the two-photon resonance transitions in a parametric region. It is found that in two-photon resonance case, the weak microwave field can reduce the threshold of optical bistability and strong microwave field can lead to optical multistability. The effect of relative phase between applied fields is also discussed. It is shown that for weak and strong microwave field, intensity threshold of OB and OM can be modified. Moreover, it is found that for strong microwave field, relative phase has an essential role for switching between OB and OM or vice versa.     

Coherent Control of Absorption Resonances via Antirotating Coupling

Effects of the antirotating coupling on the absorption resonances are presented for a microwave driven three-level system. It is shown that nonlinear sideband generation, selective suppression and switching between peaks and dips in the absorption spectrum are obtained as the microwave Rabi frequency is varied. A physical explanation is given in terms of the coherent superposition of an infinite set of transitions that are associated with an infinite set of dressed states, which are created by the rotating and nonrotating couplings as the equivalent bichromatic excitation.     

Optical bistability and multistability in a three-level Δ-type atomic system under the nonresonant condition

Under a nonresonant condition, we theoretically investigate hybrid absorptive-dispersive optical bistability and multistability behaviours in a three-level Δ-type system by using a microwave field to drive a hyperfine transition between two upper excited states inside a unidirectional ring cavity. We find that the optical bistability and multistability behaviours can be controlled by adjusting the intensity of the microwave field or the intensity of the coherent coupling field. Furthermore, our studies show an interesting phenomenon of the transition from the optical bistability to the optical multistability only by changing the negative detuning of the coupling field into the positive detuning of the coupling field.     

非共振条件下∧型三能级原子系统光学双稳态和多稳态的控制

非共振条件下,我们理论研究了单向环形光腔中用一微波场驱动一个超精细低能态跃迁的∧型三能级原子系统光学双稳态和多稳态行为,结果表明原子介质双稳态的行为可以分别通过耦合场的强度和耦合场频率的失谐量控制,同时还发现微波场在实现多稳态过程中所起的重要作用.最后讨论了合作参数对光学多稳态阈值的影响.     

Optical bistability via amplitude and phase control of a microwave field

We investigate the steady-state optical bistability behavior in a three-level Λ-type atomic system closed by a microwave field under the condition that the applied fields are in resonance with corresponding atomic transitions. It is shown that the bistable hysteresis cycles can be controlled by both the amplitude and the phase of the microwave field.     

Controlling the optical bistability and transmission coefficient in a four-level atomic medium

A novel four level atomic configuration is proposed for controlling the optical bistability and transmission coefficient with application on all-optical switching. Two circularly polarized components from a weak linearly-polarized probe beam are interacted separately by two transitions of this medium. A coherent coupling field has derived another atomic transition. It is demonstrated that the transmission coefficient of two orthogonally polarized beams at different frequencies can be achieved by adjusting the magnitude of the external magnetic field. It is found that the threshold of the optical bistability can be controlled by magnitude of the external magnetic field. Also, it is shown that optical bistability can be converted to optical multistability by switching the two orthogonally polarized beams.     

Optical bistability and multistability via amplitude and phase control in a Duplicated two-level system

We investigate the optical bistability(OB) in a duplicated two-level system contained in a ring cavity.The atoms are driven by two orthogonally polarized fields with a relative phase.The OB behavior of such a system can be controlled by the amplitude and the relative phase of the coupling field,and it is possible to switch between bistability and multistability by adjusting the relative phase.     

Control of the switch between optical multistability and bistability in three-level V-type atoms

We theoretically investigated a hybrid absorptive-dispersive optical bistability and multistability behaviour in a three-level V-type system using a microwave field driving a hyperfine transition between two upper excited states inside a unidirectional ring cavity. We find that the intensity and the frequency detuning of the coupling field as well as the intensity of the microwave field can affect the OM behaviour dramatically, which can be used to control the transition from OM to OB or vice versa without need to resort the effect of the quantum interference. The effects of the phase, the quantum interference and the atomic cooperation parameter on the OM are also studied. Our scheme may be used for building more efficient all-optical switches and logic-gate devices for optical computing and quantum information processing.     

Controllable optical bistability and multistability in asymmetric double quantum wells via spontaneously generated coherence

We investigate the nonlinear optical phenomena of the optical bistability and multistability via spontaneously generated coherence in an asymmetric double quantum well structure coupled by a weak probe field and a controlling field. It is shown that the threshold and hysteresis cycle of the optical bistability can be conveniently controlled only by adjusting the intensity of the SGC or the controlling field. Moreover, switching between optical bistability and multistability can be achieved. These studies may have practical significance for the preparation of optical bistable switching device.     

Phase-dependent optical bistability and multistability in a semiconductor quantum well system

We theoretically investigate the hybrid absorptive-dispersive optical bistability and multistability in a four-level inverted-Y quantum well system inside a unidirectional ring cavity. We find that the coupling field, the pumping field as well as the cycling field can affect the optical bistability and multistability dramatically, which can be used to manipulate efficiently the threshold intensity and the hysteresis loop. The effects of the relative phase and the electronic cooperation parameter on the OB and OM are also studied. Our study is much more practical than its atomic counterpart due to its flexible design and the wide adjustable parameters. Thus, it may provide some new possibilities for technological applications in optoelectronics and solid-state quantum information science.