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.     

Linear Amplifier and Quasiprobability Distribution Functions for the Squeezed Displaced Fock States

The nondiagonal P-function (complex andpositive) for the output field with the squeezedcoherent state as an initial state to a linear amplifieris obtained. Moments of the field operators arecalculated. The Wigner distribution function for the outputof a linear amplifier is discussed. The input lightfield of the linear amplifier is assumed to be asqueezed displaced Fock state. Investigation of theWigner distribution functions at the output fields iscarried out, where it is found that the distributionspreads out as it rotates in the phase space with timedevelopment. For the case of a squeezed displaced Fock state input it is found that thedistribution disintegrates into two subdistributions.The phase distribution for the output light is discussedthrough the phase function associated with the Wigner function for different inputs.     

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.     

Generation of Superpositions of Coherent States Along a Straight Line via Raman Interaction

We present an alternative scheme for preparing the superpositions of coherent states along a straight line of a cavity field using degenerate atom-cavity field Raman interaction. In the scheme, a collection of A-type three-level atoms is orderly sent through the cavity to interact with the cavity field adjusted by a microwave source connected to it, followed by state-selective measurements. In this way, we can prepare the superpositions of several coherent states along a straight line with arbitrary weighting factors for the cavity field. In the scheme, the coherence of the atom-cavity system may be maintained and the second microwave field is unnecessary, which is prior to the previous scheme.     

Generation of Superpositions of Coherent Interaction States Along a Straight Line via Raman Interaction

We present an alternative scheme for preparing the superpositions of coherent states along a straight line of a cavity field using degenerate atom-cavity field Raman interaction. In the scheme, a collection of A-type three-level atoms is orderly sent through the cavity to interact with the cavity field adjusted by a microwave source connected to it, followed by state-selective measurements. In this way, we can prepare the superpositions of several coherent states along a straight line with arbitrary weighting factors for the cavity field. In the scheme, the coherence of the atom-cavity system may be maintained and the second microwave field is unnecessary, which is prior to the previous scheme.     

利用V型三能级原子与单模光场的非共振相互作用制备压缩相干态的叠加态

介绍了单模压缩相干态及其基本性质,根据简并V型三能级原子与单模光场的改进型有效哈密顿量,通过矩阵方法推导出原子-光场系统的态矢量.提出利用简并V型三能级原子与单模光场的非共振相互作用制备压缩相干态的叠加态的一种新方案,讨论了怎样进行控制单模压缩相干态光场中的压缩方向问题.     

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.     

Teleportation of Unknown Superpositions of Collective Atomic Coherent States

We propose a scheme to teleport an unknown superposition of two atomic coherent states with different phases.Our scheme is based on resonant and dispersive atom-field interaction.Our scheme provides a possibility of teleporting macroscopic superposition states of many atoms first time.     

在依赖强度耦合Jaynes-Cummings模型中制备光场的相干态的叠加态

提出一个制备光场具有可控制的权重因子和相位和相干位态的叠加态的方案。它是基于在依赖强度耦合Ｊａｙｎｅｓ－Ｃｕｍｍｉｎｇｓ模型中对通过腔中的原子进行选择测量。     

Nonclassicality and Entanglement of Photon-Subtracted Two-Mode Squeezed Coherent States Studied via Entangled-States Representation

We theoretically introduce a kind of non-Gaussian entangled states, i.e., photon-subtracted two-mode squeezed coherent states (PSTMSCS), by successively subtracting photons from each mode of the two-mode squeezed coherent states. The normalization factor which is related to bivariate Hermite polynomials is obtained by virtue of the two-mode squeezing operator in entangled-states representation. The sub-Poissonian photon statistics, antibunching effects, and partial negative Wigner function, respectively, are observed numerically, which fully reflect the nonclassicality of the resultant states. Finally, employing the SV criteria and the EPR correlation, respectively, the entangled property of PSTMSCS is analyzed. It is shown that the photon subtraction operation can effectively enhance the inseparability between the two modes.     

Superpositions and Entanglement of Mesoscopic High-order Squeezed Vacuum States in Cavity QED

We propose a scheme for generating the superpositions and the entanglement between the mesoscopic high-order squeezed vacuum states by considering the multi-photon interaction of N two-level atoms in a cavity with high quality factor, assisted by a strong driving field. In terms of specific choices of the cavity detuning, many multiparty entangled states between the atoms and the mesoscopic high-order squeezed vacuum states and among the high-order squeezed vacuum states of the cavity modes can be generated, including the macroscopic “Schr?dinger cats” of the mesoscopic high-order squeezed vacuum states, the entanged states of the macroscopic “Schr?dinger cats”, and so on. Our scheme is achievable within the current techniques in the cavity QED.     

相干态与压缩态迭加的量子特性

基于量子力学基本理论,构造了一个由相干态与单模压缩态构成的新迭加态:|φ>=N(|α> eiψ|β>g);详细讨论了其压缩效应和光子数反聚束效应,发现该迭加态呈现出多样的量子特性.在按类似奇偶相干态的方式迭加时,迭加态具有奇偶相干态和压缩奇偶相干态的某些特性.作为特例,当压缩因子为0时,可以得到奇偶相干态和相干态.     

Statistical Properties of Photon-Added Two-Mode Squeezed Coherent States

The nonclassical and non-Gaussian quantum states—photon-added two-mode squeezed coherent states have been theoretically introduced by adding multiple photons to each mode of the two-mode squeezed coherent states. Starting from the new expression of two-mode squeezing operator in entangled states representation, the normalization factor is obtained, which is directly related to bivariate Hermite polynomials. The sub-Poissonian photon statistics, cross-correlation between two modes, partial negative Wigner function are observed, which fully reflect the nonclassicality of the target states. The negative Wigner function often display non-Gaussian distribution meanwhile. The investigations may provide experimentalists with some better references in quantum engineering.     

Nonclassical Properties of Multiple-Photon-Added Two-Mode Squeezed Coherent States

We investigate how the photon addition operation affects the nonclassical properties of the non-Gaussian squeezed state generated by adding photons to each mode of the two-mode squeezed coherent state (TMSCS). By the generating function of two-variable Hermite polynomials, the compact expression of normalization factor is derived. We show that the fields in such states exhibit remarkable sub-Poissonian photon statistics. The photon addition operation can enhance the cross-correlation for appropriate combinations of several parameters involved in the TMSCS. Compared with that of TMSCS, the Wigner function of the photon–added TMSCS (PA-TMSCS) is modulated by a factor which is also related with two-variable Hermite polynomials. Such Wigner functions have some negativity regions and show a strong quantum mechanical interference. In addition, the normalization factor, Mandel’s Q parameter, cross-correlation function and Wigner functions are all sensitive to the compound phase involved in TMSCS.     

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.     

Strong-Driving-Assisted Preparation of Superpositions of Two-Mode Coherent States in Cavity QED

A scheme is proposed for preparing the superposition of two-mode coherent states with controllable weighting factors along a straight line for two-mode cavity field. In this scheme two-level atoms driven by classical field are sent through a two-mode cavity initially in the vacuum state. Then the detection of the atoms make the cavity field be in a two-mode superpositions of coherent states.     

Coherent and Squeezed States for Light in Homogeneous Conducting Linear Media by an Invariant Operator Method

With the choice of Coulomb gauge, we investigated coherent state and squeezed state of the light propagating through homogeneious conducting linear media with no charge density using quantum results of the LR invariant operator method. We described coherent and squeezed properties of electric and magnetic fields. The fields in coherent and squeezed states are decayed exponentially with time due to the conductivity of the media. We studied probability density of the coherent wave packet and the highly squeezed wave packets. The uncertainty relation between the two orthogonal phase amplitudes, â₁ and â₂, in coherent state is same as the uncertainty relation in vacuum number state. The envelope of the relative noise in coherent state alternately become large and small with time and position. The uncertainty relation between canonical variables are varied depending on the value of conductivity in squeezed state, but not lowered below /2 which is quantum-mechanically acceptable minimum uncertainty.     

Generation of Superpositions of Atomic Coherent States Through Raman Atom-Field Interaction

We propose a scheme for the generation of superpositions of collective atomic coherent states. In the scheme a collection of degenerate A-type three-level atoms is confined in a high-Q cavity and interacts with the cavity field in a Raman manner. Then a state reduction on the field collapses the atomic system onto a superposition state.     

相位差与一般相干迭加态压缩特性

研究一般相干态的迭加态|ψ＞=a|β＞ beiψ|mβeiδ＞的k次方压缩特性,结果表明:一般相干态的迭加态和量子涨落的k次方压缩,在m=1时可表为k≠2nπ/δ,此处n是整数;在m≠1时,压缩的次方数可以是偶数也可以是奇数;当δ=π时,无论m[m∈(0.∞)]取何值均存在奇次方压缩,当δ=π/2时,无论m取何值均存在奇次方压缩和偶次方压缩.这说明参数相位差δ对一般相干态的k次方压缩的次方数起关键性的作用.     

Entanglement of Two-Mode Squeezed Even and Odd Coherent States

The two-mode squeezed even and odd coherent states are quantum states with some non-classical properties. The entanglement of two-mode squeezed even and odd coherent states are measured by non-classicality of P-function and separability inequalities of EPR-operators.