玻色-爱因斯坦凝聚原子处于电磁诱导透明时的压缩特性

计算和分析了玻色-爱因斯坦凝聚原子处于电磁诱导透明时的压缩特性.研究了参量对单模和双模压缩的影响.指出要增大单模压缩量可增大该模场的初始强度,减小两模间的相互作用强度.要增大双模压缩,可增大二模场的初始强度和两模间的相互作用.     

对相干态与两个原子的相互作用过程中原子与场的动力学特性

研究了对相干态(paircoherentstate)与两个二能级原子的相互作用过程中原子和场的动力学特性,并讨论了原子间的偶极相互作用对它们的影响.结果表明:辐射场的压缩以及和压缩(sumsqueezing)的幅度,出现的次数均随原子间的耦合强度的增加而迅速减小.当两个模之间的光子数差增大时,辐射场的压缩以及和压缩的幅度,出现的次数均随之减小,辐射场的两模之间的非经典相关程度减弱,模1的亚泊松分布减弱.在原子的崩溃区域,模2的亚泊松分布增强.增大q将加快原子和双模光场的能量交换. 关键词：     

Λ型和V型三能级原子与耦合腔相互作用系统中场的量子特性

研究了能级结构分别为Λ型三能级和V型三能级结构的两个原子和通过光纤耦合的由双模腔构成的复合系统中光场的压缩效应、二阶相干度和亚泊松分布等量子特性。利用数值计算方法讨论了光纤模与腔场间的耦合强度对量子特性的影响。研究结果表明:双模光场不呈现压缩效应,但呈现出反关联和亚泊松分布的量子特性;随着光纤模与腔场间耦合强度的增强,亚泊松分布减弱。     

三参数双模压缩粒子数态的量子特性

利用有序算符内的积分技术,给出了三参数双模压缩算符,构建了三参数双模压缩粒子数态,并且研究了该量子态的压缩效应、反聚束效应和对Cauchy-Schwartze不等式的违背.给出了量子态产生压缩效应和反聚束效应的条件,以及三参数双模压缩粒子数态的Wigner函数的解析式.讨论了参数变化和光子数变化对压缩效应、反聚束效应和Cauchy-Schwartze不等式的违背的影响.研究结果表明:随光子数的增大,压缩效应、反聚束效应和光场两模间的非经典相关性减弱;另一方面,随参数模的增大,压缩效应增强,但反聚束效应和光场两模间的非经典相关性却减弱.     

Kerr介质中双原子-压缩真空场系统的腔场谱

研究了含Kerr介质腔中耦合双原子间与双模均处于压缩真空态的光场拉曼相互作用过程的腔场谱.通过求解本征方程导出了双模光场处于任意强度时腔场谱的计算公式,给出了数值计算结果.发现在两模初始场均为弱场时,Kerr介质和原子间的耦合作用对谱结构的影响较小;当双模初始场均为强场时,两模主峰的右侧出现了半梳状边峰,随Kerr效应的增强,峰间距逐渐加宽,并向高频方向扩展,在Kerr效应较强时,两模边峰的峰高出现高低相间的现象.     

双模SU(1,1)相干态光场与V-型三能级原子玻色-爱因斯坦凝聚体相互作用系统中光场的压缩特性

在双模SU(1,1)相干态光场和V-型三能级原子玻色-爱因斯坦凝聚体相互作用系统中,应用全量子理论,在旋波近似下,研究了双模光场的压缩特性,分别讨论了光场与原子之间的耦合常数、原子之间的相互作用和光场参数对光场压缩特性的影响.研究表明,光场的两个正交分量均被周期性压缩,光场与原子的耦合系数和原子间的相互作用强度增大时均使得光场正交分量涨落的周期缩短;光场参数的变化不影响光场压缩的周期,对压缩深度有一定的影响.     

与非等同双原子相互作用下光场的相干性质

研究了具有不同偶极矩的两个原子与双模压缩真空场相互作用系统中光场的相干性质.讨论了两个原子与双模压缩真空场的相对耦合常量(R=g1/g2)和光场的初始压缩因子r对二阶相干度、光场的模间相关性、Cauchy-Schwartz不等式的影响.结果表明,光场的初始压缩因子较小时,光子的聚束效应和反聚束效应交替出现,且光场的模间相关程度较强.光场的初始压缩因子较大时,光子呈现聚束效应,且模间相关程度较弱.双原子的相对耦合常量R对二阶相干度、光场的模间相关性、Cauchy-Schwartz不等式的时间演化规律有影响,但不能改变光场模间相关的非经典性质.     

由NOPA产生高质量明亮压缩光及明亮EPR光束

通过非简并光学参量放大器获得了明亮双模正交压缩光及明亮EPR光束.实验测得明亮耦合模的正交振幅压缩为57±02dB;信号模与闲置模的正交振幅和(正交位相差)的起伏低于散粒噪声极限54±02dB(54±02dB),EPR关联的乘积为0332±0003. 关键词： 明亮双模正交压缩光 明亮EPR光束 非简并光学参量放大器     

双模压缩真空态在激光过程中的退相干

利用热纠缠态表象求解密度算符主方程方法,考虑双模压缩真空态中的一模经过激光过程衰减的情况,给出了双模压缩真空态在该过程中密度算符的演化规律。采用数值计算方法,讨论了一模的衰减和压缩参数变化对态的压缩效应、反聚束效应、Cauchy-Schwartze不等式违背和两模间纠缠等量子特性的影响。研究结果表明:随耗散时间增大,光场的压缩效应、反聚束效应、Cauchy-Schwartze不等式违背和两模间纠缠等特性都逐渐减弱,直至消失。另一方面,随双模压缩参数增大,压缩效应、反聚束效应、Cauchy-Schwartze不等式违背和两模间纠缠等量子特性均增强。     

与原子依赖强度耦合双模压缩真空态的量子纠缠

在考虑原子与双模光场依赖强度耦合双光子共振相互作用的条件下,应用量子相对熵研究了双模压缩真空场模间纠缠度的演化.结果表明,在原子与光场相互作用之后,模间纠缠度作周期性的变化.在强场条件下,模间纠缠度总是在初始时刻达到最大值,其变化幅度基本保持不变.在初始场很弱的条件下,纠缠度演化的特点与原子初始状态有关,当原子处于激发态和基态的等概率叠加态时,纠缠度变化的幅度最大.控制原子与光场的作用时间及原子的初态,可以调整双模光场间的纠缠.     

Detaching two single-mode squeezing operators from the two-mode squeezing operator

It has been common knowledge that the single-mode squeezing operator and the two-mode squeezing operator are independent of each other. However, in this work we find that after using the technique of integration within Ω-ordering and β-ordering, we can detach two single-mode squeezing operators from the two-mode squeezing operator. In other words, we show that the two-mode squeezing operator can be split into a β-ordered two-mode squeezing operator （with a new squeezing parameter） and two single-mode squeezing operators （with another squeezing parameter）. This tells us that the two-mode squeezing mechanism also involves some single-mode squeezing.     

Quantum entanglement and nonlocality properties of two-mode Gaussian squeezed states

Quantum entanglement and nonlocality properties of a family of two-mode Gaussian pure states have been investigated. The results show that the entanglement of these states is determined by both the two-mode squeezing parameter and the difference of the two single-mode squeezing parameters. For the same two-mode squeezing parameter, these states show larger entanglement than the usual two-mode squeezed vacuum state. The violation of Bell inequality depends strongly on all the squeezing parameters of these states and disappears completely in the limit of large squeezing. In particular, these states can exhibit much stronger violation of local realism than two-mode squeezed vacuum state in the range of experimentally available squeezing values.     

Symplectic Group Representation of the Two-Mode Squeezing Operator in the Coherent State Basis

We find that the coherent state projection operator representation of the two-mode squeezing operator constitutes a loyal group representation of symplectic group, which is a remarkable property of the coherent state. As a consequence, the resultant effect of successively applying two-mode squeezing operators are equivalent to a single squeezing in the two-mode Fock space. Generalization of this property to the 2n-mode case is also discussed.     

Symplectic Group Representation of the Two-Mode Squeezing Operator in the Coherent State Basis

We find that the coherent state projection operator representation of the two-mode squeezing operator constitutes a loyal group representation of symplectic group, which is a remarkable property of the coherent state. As a consequence, the resultant effect of successively applying two-mode squeezing operators are equivalent to a single squeezing in the two-mode Fock space. Generalization of this property to the 2n-mode case is also discussed.     

利用置于光腔中的非线性耦合器制备压缩和连续变量纠缠光

利用置于光腔中的非线性耦合器制备了压缩和连续变量纠缠光.通过特征函数方法解析求解了双模腔场满足的主方程.分析发现：在一定的条件下,此系统能产生稳定的双模压缩和连续变量纠缠光,且压缩和纠缠的强度与系统的耦合参量及腔场损耗系数密切相关.     

在两个耦合的量子点和腔QED系统中的双模激子的压缩性质(英文)

本文研究了在两个耦合的量子点和腔QED系统中的双模激子的压缩性质.讨论了不同的初始光场对双模激子的正常压缩与和压缩的影响.计算表明,当初始态光场制备在相干态时,双模激子既不存在正常压缩,也不存在和压缩,这说明双模激子振辐的两个正交分量具有相同的量子涨落;然而,当初始腔场处于压缩真空态时,无论是正常压缩还是和压缩,双模激子振辐的两个正交分量总有一个存在压缩.这意味着量子噪声能被有效的得到抑制.此外,两种情形下的最大压缩都由初始腔场的压缩因子r决定.经过比较,我们还发现双模激子的正常压缩比和压缩大.     

Coherence and Squeezing of Bose-Einstein Condensates in Double Wells

We investigate coherence and squeezing of a two-mode Bose-Einstein condensate trapped in a double-well potential. By analytically deriving the form of coherence and numerically calculating the squeezing parameter, we show that the coherence and the squeezing may be controlled by adjusting some parameters of the two-mode Bose-Einstein condensate.     

双模双光子关联发射激光的稳态特性及其量子噪声压缩特性

采用非线性量子理论研究双模双光子关联发射激光的稳态行为及其量子噪声的压缩特性．证明了在没有触发信号的情况下，系统一方面可以建立双模无反转激光，另一方面可以呈现双模滞后现象．指出了在稳态时相对振幅和平均相位量子噪声压缩的特点 关键词：     

Quantum entanglement between the two-mode fields and atomic entropy squeezing in the system of a moving atom interacting with two-mode entangled coherent field

This paper investigates the entropy squeezing of a moving two-level atom interacting with the two-mode entangled coherent field via two-photon transition by using an entropic uncertainty relation and the degree of entanglement between the two-mode fields by using quantum relative entropy. The results obtained from numerical calculation indicate that the squeezed period, the duration of entropy squeezing and the maximal squeezing can be controlled by appropriately choosing the intensity of the light field, the atomic motion and the field-mode structure. The atomic motion leads to the periodic recovery of the initial maximal degree of entanglement between the two-mode fields. Moreover, there exists a corresponding relation between the time evolution properties of the atomic entropy squeezing and those of the entanglement between the two-mode fields.     

三能级原子与奇偶纠缠相干光作用的光场压缩

采用求解薛定谔方程和数值计算方法,研究了V型三能级原子与双模奇偶纠缠相干光场相互作用过程中的光场压缩效应,讨论了压缩效应与双模奇偶纠缠相干光场的纠缠程度、系统失谐量、双模光场的平均光子数和原子基态概率幅的依赖关系。结果表明：光场压缩效应与双模奇偶纠缠相干光场的纠缠程度、失谐量、平均光子数和原子初态相关联：双模纠缠相干光场处于非纠缠状态时的光场压缩量比光场处于纠缠状态时要大;原子处在单纯的基态或激发态时光场都有明显的压缩现象出现;而原子初态中基态和激发态的概率幅较接近时无光场压缩现象;无论光场是否处于纠缠态,只有两模平均光子数接近时,光场才会出现压缩效应。