量子光学中的非经典态

本文扼要地介绍了光子数态、热光场态、相干态、压缩态、相位态和中间态等。重点是介绍它们的物理性质。例如,指出相干态在谐振子座标表象中的表示就是带电谐振子在均匀电场中的基态波函数;它的时间演化波包的概率密度分布,形状不随时间变但中心位置随时间作周期振荡。文中对相干态和压缩态等提供了也许是一点新的看法：将相干态、压缩真空态、压缩相干态和相干压缩态等看作是一准玻色子的基态或相干态。而实现的手段可以是原来的幺正算符也可以是投影算符。这样的好处是：（１）对相干态和压缩态间的联系有更深的认识;（２）便于计算和进一步展开等等。文中还对各个态的压缩性、统计性等作了介绍,有的还用图表等演示了它们的非类经典特性。最后,文中还介绍了准概率分布函数、相空间技术以及它们的应用并给出了示例     

q变形带电Fermion相干态和q’变形的SU(3)电荷、超荷Fermion相干态

利用q变形的Fermion振子代数讨论了q变形的带电Fermion相干态和q变形的SU(3)电荷、超荷Fermion相干态.利用q-FermionFock空间中的基失的完闭性,得到上述两种相干态的具体表现形式.将q变形的结果与普通结果比较发现:在变形参数q=1时,q变形的带电Fermion相干态和SU(3)电荷、超荷Fermion相干态自然回到普通的带电Fermion相干态和SU(3)电荷、超荷Fermion相干态.     

量子扩散方程的导出和相干态在扩散通道中的演化

我们利用相干态表象将经典扩散方程自然地推广到量子力学形式,并讨论了相干态在扩散通道中的演化问题,发现相干纯态在扩散通道中会演化为混态,并给出任意时刻的终态表达式。同时,我们得到光子数在扩散通道中会增加。     

量子光学中的非经典态

本文扼要地介绍了光子数态、热光场态、相干态、压缩态、相位态和中间态等。重点是介绍它们的物理性质。例如，指出相干态在谐振子座标表象中的表示就是带电谐振子在均匀电场中的基态波函数；它的时间演化波包的概率密度分布，形状不随时间变但中心位置随时间作周期振荡。文中对相干态和压缩态等提供了也许是一点新的看法：将相干态、压缩真空态、压缩相干态和相干压缩态等看作是一准玻色子的基态或相干态。而实现的手段可以是原来的幺正算符也可以是投影算符。这样的好处是：（１）对相干态和压缩态间的联系有更深的认识；（２）便于计算和进一步展开等等。文中还对各个态的压缩性、统计性等作了介绍，有的还用图表等演示了它们的非类经典特性。最后，文中还介绍了准概率分布函数、相空间技术以及它们的应用并给出了示例     

内禀退相干下薛定谔猫态光场与原子相互作用系统的场熵演化

通过求解系统的Milburn方程,研究了二能级原子与薛定谔猫态光场相互作用系统中的场熵演化特性.讨论了内禀退相干,光场强度,相干态间的相位角对场熵演化的影响.结果表明: 内禀退相干下,随着时间的演化,场熵振荡逐渐减弱,光场与原子的纠缠度逐渐趋于恒值.并且光场与原子的最大纠缠度值只取决光场强度和相干态间的相位角,与内禀退相干因子无关.光场强度较小时,奇相干态光场与原子的纠缠度最大;偶相干态光场与原子的纠缠度值为最小;Yurke-Stoler相干态光场与原子的纠缠度值介于两者之间. 当内禀退相干因子不变、光场强度较大时,分别处于Yurke-Stoler相干态、偶相干态和奇相干态的光场与原子的纠缠度值趋近于相同.     

内禀退相干下薛定谔猫态光场与原子相互作用系统的场熵演化

通过求解系统的Milburn方程,研究了二能级原子与薛定谔猫态光场相互作用系统中的场熵演化特性.讨论了内禀退相干,光场强度,相干态间的相位角对场熵演化的影响.结果表明: 内禀退相干下,随着时间的演化,场熵振荡逐渐减弱,光场与原子的纠缠度逐渐趋于恒值.并且光场与原子的最大纠缠度值只取决光场强度和相干态间的相位角,与内禀退相干因子无关.光场强度较小时,奇相干态光场与原子的纠缠度最大;偶相干态光场与原子的纠缠度值为最小;Yurke-Stoler相干态光场与原子的纠缠度值介于两者之间. 当内禀退相干因子不变、光场强度较大时,分别处于Yurke-Stoler相干态、偶相干态和奇相干态的光场与原子的纠缠度值趋近于相同.     

双模纠缠相干态正交基的构建与纠缠度的计算

纠缠相干态是一类在量子信息领域有重要应用的连续变量纠缠态,由于相干态表象中的基矢不正交,导致其纠缠度计算的困难.本文给出了基于相干态本身的正交归一完备基的构建方法,简化了其纠缠度的计算,讨论了纠缠度的影响因素,并计算了常见的几种纠缠相干态的纠缠度.     

q变形带电Fermion相干态和q’变形的SU（3）电荷、超荷Fermion相干态

利用ｑ变形的Ｆｅｒｍｉｏｎ振子代数讨论了ｑ变形的带电Ｆｅｒｍｉｏｎ相干态和ｑ变形的ＳＵ（３）电荷、超荷Ｆｅｒｍｉｏｎ相干态．利用ｑ－ＦｅｒｍｉｏｎＦｏｃｋ空间中的基失的完闭性，得到上述两种相干态的具体表现形式．将ｑ变形的结果与普通结果比较发现：在变形参数ｑ＝１时，ｑ变形的带电Ｆｅｒｍｉｏｎ相干态和ＳＵ（３）电荷、超荷Ｆｅｒｍｉｏｎ相干态自然回到普通的带电Ｆｅｒｍｉｏｎ相干态和ＳＵ（３）电荷、超荷Ｆｅｒｍｉｏｎ相干态．     

Landau规范下均匀磁场中带电粒子圆心相干态计算

在Ｌａｎｄａｕ规范下计算出均匀磁场中带电粒子的圆心相干态。利用这些圆心相干态可方便地描述带电粒子的圆周运动。这些圆周运动与经典力学的结果比较表明，圆心相干态描述系综中的平均运动． 关键词：     

量子相干破坏信道的研究

量子相干态和量子纠缠态在量子计算中具有同等重要的地位,都是量子计算中重要的物理资源。量子相干态可用来制备量子纠缠态,一个量子相干态和一个辅助量子不相干态通过不相干操作可产生量子纠缠态。根据纠缠破坏信道原理提出输入分别是单体最大相干态和二体最大相干态的相干破坏信道,该信道将输入的相干态转化为不相干态,并简单验证了提出的相干破坏信道是否真正破坏了输入的量子相干态的相干性。同时提出量子相干破坏信道可作为检测量子态的相干性一种新的方法。     

增光子二模纠缠相干态的纠缠特性及其通过腔量子电动力学的制备

分析了增光子二模纠缠相干态的纠缠特性,得到共生纠缠度的解析表示式.结果表明:增光子二模纠缠相干态的共生纠缠度与叠加态的相位有非常灵敏的关系.提出了一种制备增光子相干态和增光子二模纠缠相干态的方法,其制备过程为首先把增光子相干态转化为相干态与真空态一种特殊的叠加态(叠加系数与相干态振幅有关),再通过位于高Q腔内的原子与经典激光场的相互作用,从而实现增光子相干态的制备.通过一个飞行原子先后与两个光腔中光场相互作用可以实现增光子二模纠缠相干态的制备.     

增光子二模纠缠相干态的纠缠特性及其通过腔量子电动力学的制备

分析了增光子二模纠缠相干态的纠缠特性,得到共生纠缠度的解析表示式.结果表明:增光子二模纠缠相干态的共生纠缠度与叠加态的相位有非常灵敏的关系.提出了一种制备增光子相干态和增光子二模纠缠相干态的方法,其制备过程为首先把增光子相干态转化为相干态与真空态一种特殊的叠加态(叠加系数与相干态振幅有关),再通过位于高Q腔内的原子与经典激光场的相互作用,从而实现增光子相干态的制备.通过一个飞行原子先后与两个光腔中光场相互作用可以实现增光子二模纠缠相干态的制备.     

Coherent and squeezed states on physical basis

A definition of coherent states is proposed as the minimum uncertainty states with equal variance in two hermitian non-commuting generators of the Lie algebra of the hamiltonian. That approach classifies the coherent states into distinct classes. The coherent states of a harmonic oscillator, according to the proposed approach, are shown to fall in two classes. One is the familiar class of Glauber states whereas the other is a new class. The coherent states of spin constitute only one class. The squeezed states are similarly defined on the physical basis as the states that give better precision than the coherent states in a process of measurement of a force coupled to the given system. The condition of squeezing based on that criterion is derived for a system of spins.     

Multi-matrix vector coherent states

A class of vector coherent states is derived with multiple of matrices as vectors in a Hilbert space, where the Hilbert space is taken to be the tensor product of several other Hilbert spaces. As examples vector coherent states with multiple of quaternions and octonions are given. The resulting generalized oscillator algebra is briefly discussed. Further, vector coherent states for a tensored Hamiltonian system are obtained by the same method. As particular cases, coherent states are obtained for tensored Jaynes-Cummings type Hamiltonians and for a two-level two-mode generalization of the Jaynes-Cummings model.     

一种新的偶奇非线性相干态中测量相位算符的压缩效应

利用Bamett和pegg提出的测量相位算符讨论了一种新的偶奇非线性相干态的压缩效应。结果表明，在这种偶奇非线性相干态中测量相位算符不存在CN和SN类压缩，只存在CS类压缩。利用数值计算方法研究了CS类压缩效应，结果表明与通常的偶奇相干态的不同的是，偶非线性相干态在大区域内出现压缩效应而奇非线性相干态在小区域内才出现压缩效应。     

压缩奇偶相干态的量子统计性质

用压缩算子作用在奇偶相干态上即可得到压缩奇偶相干态.本文研究了这类量子态的统计特性.结果表明,压缩奇相干态和压缩偶相干态都能处于压缩状态,它们的光子亦都可能出现反聚束的现象.     

Preparation of Highly Squeezed States and Multi—component Entangled Coherent States via the Raman Interaction

A method is presented for generating highly squeezed states of a cavity field via the atom-cavity field interaction of the Raman type.In the scheme a sequence of three-level Λ-type atoms interacts with a cavity field,displaced by a classical source,in a Raman manner.Then the atomic states are measured.By this way the cavity field may collapse onto a superposition of several coherent states,which exhibits strong squeezing.The scheme can also be used to prepare superpositions of many two-mode coherent states for two cavity fields.The coherent states in each mode are on a straight line.This is the first way for preparing multi-component entangled coherent states of this type in cavity QED.     

Schemes for performance of displacing Hadamard gate with coherent states

We propose an approach with displaced states to use it for rotations of base coherent states and squeezed coherent states. Our approach is based on representation of the coherent states in free-traveling fields in terms of displaced number states with arbitrary amplitude of displacement. Two optical schemes are developed for construction of Hadamard gate for the base states. One of the optical schemes is based on alternation of photon additions and displacement operators (in general case, N-photon additions and N?1-displacements are required) to generate displaced squeezed even/odd superposition of coherent states (SCSs) with high fidelity in dependency on type (computational zero or one) of the base input state. Another optical scheme uses two-photon subtracted squeezed coherent states to approximate outcome of the Hadamard gate for the base squeezed coherent states. Output states approximate with high fidelity either even squeezed SCS or odd SCS shifted relative to each other by some value. It enables to adjust the optical scheme for construction of the Hadamard gate being mainframe element for quantum computation with basic squeezed coherent states.     

Coherent States and Modified de Broglie-Bohm Complex Quantum Trajectories

This paper examines the nature of classical correspondence in the case of coherent states at the level of quantum trajectories. We first show that for a harmonic oscillator, the coherent state complex quantum trajectories and the complex classical trajectories are identical to each other. This congruence in the complex plane, not restricted to high quantum numbers alone, illustrates that the harmonic oscillator in a coherent state executes classical motion. The quantum trajectories we consider are those conceived in a modified de Broglie-Bohm scheme. Though quantum trajectory representations are widely discussed in recent years, identical classical and quantum trajectories for coherent states are obtained only in the present approach. We may note that this result for standard harmonic oscillator coherent states is not totally unexpected because of their holomorphic nature. The study is extended to coherent states of a particle in an infinite potential well and that in a symmetric Poschl-Teller potential by solving for the trajectories numerically. For the Gazeau-Klauder coherent state of the infinite potential well, almost identical classical and quantum trajectories are obtained whereas for the Poschl-Teller potential, though classical trajectories are not regained, a periodic motion results as t→∞. Similar features were found for the SUSY quantum mechanics-based coherent states of the Poschl-Teller potential too, but this time the pattern of complex trajectories is quite different from that of the previous case. Thus we find that the method is a potential tool in analyzing the properties of generalized coherent states.     

好腔中的Bell态原子与纠缠相干态光场相互作用系统的保真度

考虑原子间偶极相互作用,求出好腔中的Bell态原子与纠缠相干态光场相互作用系统的保真度。结果表明,对于理想腔,若原子初始时刻处于相干保持态,系统保真度始终等于1;若原子初始时刻处于其余Bell态之一,腔场初态的平均光子数很小,系统保真度在0～1之间作周期性振荡,随着腔场初态的平均光子数的增加,系统保真度的振荡频率增大,振幅减小。对于好腔,若原子初始时刻处于相干保持态,系统保真度呈指数单调衰减;若原子初始时刻处于其余Bell态之一,系统保真度呈指数振荡衰减,且随着腔场初态的平均光子数的增加,系统保真度的振荡频率增大,振幅减小。