增光子压缩真空态的反群聚效应

本文讨论了压缩真空态在玻色湮灭算符的逆算符及玻色产生算符作用下的光子反群聚性质. 结果表明, 在两种情况下所得到的增光子压缩真空态都呈现出反群聚效应, 但前者呈现的反群聚效应与所增加的光子数k以及压缩参数的取值区间有关, 而后者则在相同的压缩参数取值区间内呈现出反群聚效应, 与增加的光子数k无关.     

Quantum phase distribution and the number—phase Wigner function of the generalized squeezed vacuum states associated with solvable quantum systems

The quantum phase properties of the generalized squeezed vacuum states associated with solvable quantum systems are studied by using the Pegg-Barnett formalism.Then,two nonclassical features,i.e.,squeezing in the number and phase operators,as well as the number-phase Wigner function of the generalized squeezed states are investigated.Due to some actual physical situations,the present approach is applied to two classes of generalized squeezed states:solvable quantum systems with discrete spectra and nonlinear squeezed states with particular nonlinear functions.Finally,the time evolution of the nonclassical properties of the considered systems has been numerically investigated.     

Successively Squeezed States Studied by Virtue of the IWOP Technique

Two kinds of successively squeezed states which are generated by re-squeezing two single mode squeezed states by the two-mode squeezing operator, or by re-squeezing a two-mode squeezed state by two single-mode squeezing operators, are studied in terms of the newly developed technique of integration within an ordered product (IWOP) of operators. The fluctuations in quadrature phases for the resqueezed states are analyzed.     

On the deformed squeezed states on noncommutative plane

A new kind of deformed boson operators is proposed to be consistent with the large noncommutativity parameters on noncommutative plane when noncommutativity of momentum spaces is considered. Using this kind of deformed boson operators, the coherent states and squeezed states are constructed, and their properties are discussed in detail.     

Study of two-dimensional squeezed magnetopolarons

In this Letter, some properties of two-dimensional squeezed magnetopolarons are investigated. The Hamiltonian of magnetopolarons is dealt with by using squeezed state transformation, which is based on the Lee–Low–Pines and Huybrechts (LLP–H) canonical transformations. This method makes it possible to consider bilinear terms of the phonon operators as well as linear terms arising from the LLP–H transformations. Some exact results are obtained, such as the energies of ground and excited states for squeezed magnetopolarons and renormalized cyclotron masses for some possible transitions.     

Phase properties of the nonlinear squeezed vacuum states

Using properties of the inverses of annihilation and creation operators of f-oscillator we construct the f-analogues of squeezed vacuum states. If used to describe the motion of a trapped ion, the phase probability distributions of these states for large η are very different from those of the usual squeezed vacuum state.     

测不准关系和最小不确定态

利用力学量算符的厄密性和希尔伯特状态矢量模的非负性，重新给出了关于测不准关系的数 学证明.简单的证明过程不仅揭示了测不准关系某些经常被忽视的特征，而且还可以直接给 出最小不确定态的充要条件.在此基础上，我们提出了对易子为非零常数的任意一对力学量 的最小不确定态问题，并且采用玻色型产生和湮没算符给出了它们的压缩态的明显表达式. 关键词： 海森堡测不准原理 最小不确定态 压缩态     

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.     

单双模连续压缩真空态及其量子统计性质

利用有序算符内的积分技术研究了通过双模压缩算符作用于两个单模压缩 态上得到的单双模 连续压缩态. 导出了单双模连续压缩算 符的正规乘积形式, 并在此基础上研究了单双模连续压缩真空态的量子统计性质. 特别是利用Weyl编 序算符在相似变换 下的不变性, 简洁地导出了单双模连续 压缩真空态的Wigner函数. 最后, 还简单地提出 了单双模连续压缩 真空态的实验产生方案.     

The q-analogues of two-mode squeezed states constructed by virtue of the IWOP technique

The q-analogues of two-mode squeezed states are introduced by virtue of deformation quantization methods and the technique of integration within an ordered product （IWOP） of operators. Some new completeness relations about these squeezed states composed of the bra and ket which are not mutually Hermitian conjugates are obtained. Furthermore, the antibunching effects of the two-mode squeezed vacuum state S＇s（τ） │00） are investigated. It is found that, in different ranges of the squeezed parameter τ, both modes of the state exhibit the antibunching effects and the two modes of the state are always nonclassical correlation.     

Phase properties of squeezed states of light

Recently introduced unitary and hermitian phase operators are used to examine the phase properties of squeezed states of light with particular reference to the squeezed vacuum. The results differ markedly from previous calculations involving the Susskind and Glogower operators. The new formalism allows the construction of a phase probability density which, on a polar diagram, is a circle for the vacuum state, becomes elliptical with gentle squeezing and collapses to a line through the origin for full squeezing. This probability density together with the calculation of expectation values of various trigonometrical functions of phase show how squeezing impresses phase information onto the vacuum.     

Nonlinear squeezed states for SU(1,1) Lie algebra

The nonlinear extensions of the single-mode squeezed vacuum and squeezed coherent states are studied. We have constructed the nonlinear squeezed states (NLSS's) realization of SU(1,1) Lie algebra. Two cases of this realization are considered for unitary and non-unitary deformation operator function. The nonlinear squeezed coherent states (NLSCS's) are defined and special cases of these states are obtained. Some nonclassical properties of these states are discussed. The s-parameterized characteristic function and various moments are calculated. The Glauber second-order coherence function is calculated. The squeezing properties of the NLSCS's are studied. Analytical and numerical results for the quadrature component distributions for the NLSCS's are presented. A generation scheme for NLSCS's using the trapped ions centre-of-mass motion approach is proposed.     

Generation of displaced squeezed superpositions of coherent states

We study the method of generation of states that approximate superpositions of large-amplitude coherent states (SCSs) with high fidelity in free-traveling fields. Our approach is based on the representation of an arbitrary single-mode pure state, and SCSs in particular, in terms of displaced number states with an arbitrary displacement amplitude. The proposed optical scheme is based on alternation of photon additions and displacement operators (in the general case, N photon additions and N − 1 displacements are required) with a seed coherent state to generate both even and odd displaced squeezed SCSs regardless of the parity of the used photon additions. It is shown that the optical scheme studied is sensitive to the seed coherent state if the other parameters are unchanged. Output states can approximate either even squeezed SCS or odd SCS shifted relative to each other by some value. This allows constructing a local rotation operator, in particular, the Hadamard gate, which is a mainframe element for quantum computation with coherent states. We also show that three-photon additions with two intermediate displacement operators are sufficient to generate even displaced squeezed SCS with the amplitude 1.7 and fidelity more than 0.99. The effects deteriorating the quality of output states are considered.     

相位算子在单模压缩态中的行为

本文仔细讨论了相位算子在单模压缩态光场中的行为,计算了压缩态下相位算子的平均值和涨落。在得到了严格的、普遍性的结果后我们详细地讨论了压缩真空态这一特殊情形下的结果。此外,本文还讨论了严格的结果在经典极限下的渐近行为。     

Proposed Entanglement Swapping in Continuous Variable Systems via Braiding

We study entanglement swapping in continuous variable systems byusing braiding transformations. It is found that entanglement swapping in two-mode squeezed vacuum states and squeezed coherent states can be realized based on the braiding operators.     

Holstein-Primakoff/Bogoliubov Transformations and the Multiboson System

As an aid to understanding the displacement operator definition of squeezed states for arbitrary systems, we investigate the properties of systems where there is a Holstein-Primakoff or Bogoliubov transformation. In these cases the ladder-operator or minimum-uncertainty definitions of squeezed states are equivalent to an extent displacement-operator definition. We exemplify this in a setting where there are operators satisfying [A, A^å] = 1, but the A's are not necessarily the Fock space a's; the multiboson system. It has been previously observed that the ground state of a system often can be shown to to be a coherent state. We demonstrate why this must be so. We close with a discussion of an alternative, effective definition of displacement-operator squeezed states.     

Study of Two-Mode Squeezed Magnetopolarons

In this paper, we conduct an investigation into two-dimensional squeezed magnetopolarons. The Hamiltonian of magnetopolarons is dealt with two-mode squeezed states transformation, which is based on the Lee-Low-Pines and Huybrechts （LLP-H） canonical transformations. This method makes it possible to take account of the linear terms, bilinear ones of phonon operators, and the correlation between two longitudinal optical （LO） phonon modes. The energies of the ground state and excited states are evaluated by variational approach, and accurate results are obtained. Furthermore, the renormalized cyclotron masses for some possible transitions are discussed in detail.     

The <Emphasis Type="Italic">q</Emphasis>-Analogues of Squeezed States and Some Properties

In this paper we shall introduce two q-analogues of the squeezed states in terms of the technique of integration within an ordered product of operators and the properties of the inverses of q-deformed annihilation and creation operators, and some nonclassical properties of the states are examined. Furthermore, we obtain some new completeness relations composed of the bra and ket which are not mutually Hermitian conjugate. PACS numbers: 03.65.-w; 45.50.Ct. Work supported by the National Natural Science Foundation of China under Grant 10574060 and the Natural Science Foundation of Shandong Province of China under Grant Y2004A09.     

Degree of Entanglement for Some Bipartite Entangled Bosonic Systems

We calculate the degree of entanglement for some bipartite entangled states of continuous variables.These states include common two-mode squeezed vacuum state, thermal vacuum state of a free single particle (where theh fictitious tilde system is regarded as another particle), and the squeezed vacuum state of two coupling harmonic oscillators.The degree of entanglement for these quantum systems are shown clearly by using the technique of integration within an ordered product of operators.