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.     

Preparation of Motional Mesoscopic Superpositions of Squeezed Coherent States of N Trapped Ions

A scheme is proposed to generate arbitrary, discrete superpostions of squeezed coherent states of the squeezed center of mass of $N$ trapped ions along a straight line in phase space. The scheme is based on a resonant bichromatic excitation of each trapped ion that generates displacement and squeezing in the vibrational motion conditioned to each internal state. In this paper, we also show that such a method can be used for the engineering of motional quantum states.     

Coherent States and Squeezed States in Interacting Fock Space

In this paper we study coherent states and squeezed states in one mode interacting Fock space.     

Nonlinear Squeezed States and Multiplication Rule of Nonlinear Squeezing Operators Gained via Nonlinear Coherent State Representation and IWOP Technique

Using the nonlinear coherent state representation we derive nonlinear squeezed states and the multiplication rule of nonlinear squeezing operators. We find that the symplectic matrices multiplication rule in nonlinear coherent state projection operator representation maps into the multiplication rule of successive nonlinear squeezing operators.The technique of integral within an ordered product of operators plays an essential role in deriving the multiplication rule.     

Helstrom Bound for Squeezed Coherent States in Binary Communication

In quantum information processing, using a receiver device to differentiate between two non-orthogonal states leads to a quantum error probability. The minimum possible error is known as the Helstrom bound. In this work, we study the conditions for state discrimination using an alphabet of squeezed coherent states and compare them with conditions using the Glauber-Sudarshan, i.e., standard, coherent states.     

Nonlinear Squeezed States and Multiplication Rule of Nonlinear Squeezing Operators Gained via Nonlinear Coherent State Representation and IWOP Technique

Using the nonlinear coherent state representation we derive nonlinear squeezed states and the multiplication rule of nonlinear squeezing operators. We find that the symplectic matrices multiplication rule in nonlinear coherent state projection operator representation maps into the multiplication rule of successive nonlinear squeezing operators.The technique of integral within an ordered product of operators plays an essential role in deriving the multiplication rule.     

叠加压缩相干态的量子统计性质

研究了叠加压缩相干态的量子统计性质,给出了压缩和反聚束效应与叠加系数之间的关系。结果表明,叠加压缩相干态具有压缩和反聚束的现象。压缩奇偶相干态的有关结果均作为特例包含在本文的一般结论之中。     

The Squeezing Operator and the Squeezed States of "Superspace

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Quasiprobability Distribution Functions of Squeezed Pair Coherent States

Using the entangled state representation of Wigner operator and some formulae related to the two-variable Hermite polynomials, the Wigner function of the squeezed pair coherent state (SPCS) and its two marginal distributions are derived. Based on the entangled Husimi operator introduced by Fan et al. (Phys. Lett. A 358:203, 2006) and the Weyl ordering invariance under similar transformations, we also obtain the Husimi function of the SPCS and its marginal distribution functions. The comparison between the two quasibability functions shows that, for the same amount of information included in two functions, the solving process of the Husimi function is simpler than that of the Wigner function. Work supported by the Natural Science Foundation of Shandong Province of China under Grant Y2008A23 and the Natural Science Foundation of Liaocheng University under Grant X071049.     

Entanglement Properties of Two-Mode Squeezed Coherent States in Radiation Field

Entanglement properties of two-mode squeezed coherent states in the radiation field are investigated according to the entanglement criterion [Phys. Rev. Lett. 84 (2000) 2722]. The dependence of entanglement on squeeze angle and squeeze parameter is discussed. It shows that the system evolves into entangled states and entanglement does not increase persistently with the increase of squeeze angle and squeeze parameter. There only exists a certain squeeze angle in which the entanglement exists continuously.     

Squeezed State Caused by Inverse of Photon Creation Operator

Using the photon creation operator's eigenstate theory we derive the normally ordered expansion of inverse of the squeezed creation operator. It turns out that using this operator a kind of excitation on the squeezed vacuum states can be formed.     

Quantum Properties of Two-Mode Squeezed Even and Odd Coherent States

Two new types of quantum states are constructed by applying the operator s(ξ) = exp(ξ*ab - ξa b ) on the two-mode even and odd coherent states.The mathematical and quantum statistical properties of such states are investigated.Various nonclassical features of these states,such as squeezing properties,the inter-mode photon bunching,and the violation of Cauchy-Schwarz inequality,are discussed.The Wigner function in these states are studied in detail.     

f-Deformed Squeezed Vacuum and First Excited States,Their Superposition and Corresponding Nonclassical Properties

In this paper, we introduce two new classes of nonlinear squeezed states that we name as f-deformed squeezed vacuum state|ξ, f even and f-deformed squeezed first excited state |ξ, f odd, which according to their production processes, essentially include only even and odd bases of Fock space, respectively. In the continuation, we introduce the superposition of these two distinct nonlinear squeezed states with a respective phase ?. Then, some of the criteria which imply the nonclassicality of the states, such as Mandel parameter, second-order correlation function, quadrature squeezing, amplitude-squared squeezing, Husimi and Wigner–Weyl quasi-distribution functions, are numerically examined. At last, by considering a well-known nonlinearity function associated with a nonlinear physical system, we present our results which outcome from the numerical calculations. It is shown that, the introduced f-deformed states can reveal high nonclassical features.     

耦合双原子与单模压缩相干态光场的相互作用

利用全量子理论,在相互作用绘景中研究了两个耦合二能级原子与单模压缩相干态光场相互作用系统粒子布居几率的时间演化规律;分别讨论了光场的相干振幅分量模平方｜α｜２、光场的压缩因子γ、原子间的耦合系数g和原子-场的耦合系数λ对系统粒子布居几率的影响.     

运动纠缠双原子与压缩相干态光场相互作用系统的场熵演化

利用全量子理论,研究了运动纠缠双原子与压缩相干态光场相互作用系统的场熵演化特性,讨论了相干态振幅参量、光场压缩参量、原子的运动和场模结构参数对系统场熵的影响.结果表明:(1)原子运动导致场熵演化具有周期性.(2)随着相干态振幅参量的增大,原子与光场的纠缠度逐渐减小;而随着压缩参量的增大,原子与光场的纠缠度逐渐增大.(3)随着原子运动速度的增大或场模结构参数的增大,场熵的演化周期缩短,并且场与原子的纠缠度逐渐减小.     

Thermal Wigner Operator in Coherent Thermal State Representation and Its Application

In the coherent thermal state representation we introduce thermal Wigner operator and find that it is “squeezed” under the thermal transformation.The thermal Wigner operator provides us with a new direct and neat approach for deriving Wigner functions of thermal states.     

Wigner Distribution Function and Husimi Function of a Kind of Squeezed Coherent State

We find a new x-parameter squeezed coherent state （p, q）κ representation, which possesses well-behaved features, i.e., its Wigner function＇s marginal distribution in the ＂q-direction＂ and in the ＂p-direction＂ is the Gauss/an form exp（-κ（q＇ - q）2}, and exp{（p＇ - p）2/κ}, respectively. Based on this, the Husimi function of（p, q）κ is also obtained, which is a Gauss/an broaden version of the Wigner function. The （P, q）κ state provides a good representative space for studying various properties ot the Husimi operator.     

测量相位算符在压缩热场态中的压缩效应

利用Bannett和Pegg提出的测量相位算符讨论了压缩热场态中测量相位算符的压缩效应。结果表明测量相位算符在压缩热场态中存在CS类压缩，压缩特性与相干态参数幅角θ、平均光子数n^-和压缩参量r有密切的关系。随着n^-和r的增大，CS类压缩效应逐渐减弱，直至完全消失。另有计算表明测量相位算符在压缩热场态中不存在CN和SN类压缩。     

Evolution and Generation of Dynamics of Two-Mode Squeezed States of Time-Dependent Coupled Boson System

The system of the Hamiltonian involving a driving part, a single mode part, and a two-mode squeezed one and a two-mode coupled one is discussed using the Lewis-Riesenfeld invariant theory. The time evolution operator is obtained. When the initial state is a coherent state, the quantum fluctuation of the system is calculated, and it is dependent on the squeezed part and the two-mode coupled part, but not dependent on the driving one.     

Evolution and Generation of Dynamics of Two-Mode Squeezed States of Time-Dependent Coupled Boson System

The system of the Hamiltonian involving a driving part, a single mode part, and a two-mode squeezed one and a two-mode coupled one is discussed using the Lewis-Riesenfeld invariant theory. The time evolution operator is obtained. When the initial state is a coherent state, the quantum fluctuation of the system is calculated, and it is dependent on the squeezed part and the two-mode coupled part, but not dependent on the driving one.