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.     

Single-mode quadrature-amplitude measurement for generalized two-mode squeezed states studied by virtue of the entangled state representation

The result of one-mode quadrature-amplitude measurement for some generalized two-mode squeezed states has been studied by virtue of the entangled state representation of the corresponding two-mode squeezing operators. We find that the remaining field-mode simultaneously collapses to the single-mode squeezed state with more stronger squeezing. The measurement result caused by a single-mode squeezed state projector is also calculated, which indicates quantum entanglement in 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.     

Coordinate-Dependent One- and Two-Mode Squeezing Transformation and the Corresponding Squeezed States

We introduce the coordinate-dependent one- and two-mode squeezing transformations and discuss the properties of the corresponding one-and two-mode squeezed states. We show that the coordinate-dependent one-and two-mode squeezing transformations can be constructed by the combination of two transformations, a coordinate-dependent displacement followed by the standard squeezed transformation. Such a decomposition turns a nonlinear problem into a linear one because all the calculations involving the nonlinear one- and two-mode squeezed transformation have been shown to be able to reduce to those only concerning the standard one- and two-mode squeezed states.     

Three-Mode Cyclic Squeezed States Constructed via EPR Entangled State

We construct the three-mode cyclic squeezed states and analyze its squeezing property by using the technique of integration within an ordered product of operators and the natural representation of the two-mode squeezing operator in the Einstein-Podolsky-Rosen entangled state basis.     

Entanglement Swapping for Displaced Two-Mode Squeezed States

We discuss the entanglement swapping of two pairs of displaced two-mode squeezed states and find that the squeezing parameter of the outcoming squeezed state is less than that of the originM squeezed states. The calculation is greatly simplified by virtue of the natural expression of the two-mode squeezing operator in EPR eigenstate representation. A protocol for such entanglement swapping is proposed.``     

Two-mode squeezing in a coherently driven degenerate parametric down conversion

Squeezing properties of a two-mode radiation produced by a process of driven degenerate parametric down conversion, when the cavity is coupled to two independent squeezed vacuum reservoirs employing the linearization procedure, are analyzed. The two-mode cavity and output radiations exhibit considerable squeezing even when the oscillator is coupled to a vacuum reservoir. One of the effects of coupling the cavity to the squeezed vacuum reservoirs is to increase the degree of squeezing exponentially. For the output radiation the correlation of the quadrature operators evaluated at different times also contributes to the squeezing, which is the reason for quenching of the overall noise in one of the quadrature components of the fundamental mode.     

Higher-order squeezing of quantum electromagnetic fields and higher-order uncertainty relations in two-mode squeezed states

It is found that the two-mode output quantum electromagnetic field in two-mode squeezed states exhibits higherorder squeezing to all even orders, and the degree of higher-order squeezing is greater than that of the second-order.The higher-order squeezed parameter and squeezed limit due to the modulation frequency are investigated. The smaller the modulation frequency is, the stronger the degree of higher-order squeezing becomes. Furthermore, the higher-order uncertainty relations in two-mode squeezed states are presented for the first time. The product of higher-order noise moments is related to even order number N and the squeeze factor r.     

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.     

单-双模组合压缩热态的纠缠性质及在量子隐形传态中的应用

基于单-双模组合压缩真空态一定范围内能够获得压缩增强的效果,引入单-双模组合压缩热态(DSMST),讨论其纠缠性质.利用Weyl编序算符在相似变换下的不变性,简洁方便地导出了DSMST的纠缠度-负对数值,并给出了当热效应存在时保持纠缠的条件.研究表明:与通常的双模压缩态相比,随着参数的增加,DSMST的纠缠度增加.作为DSMST的应用,利用其实现相干态的量子隐形传输.结果表明:不同于纠缠度随压缩参数增加,保真度获得改善是有条件的,该条件恰好就是一正交分量涨落出现压缩增强的参数区域.此外,解析推导了有效隐形传输保真度(1/2)的条件.     

Photon Statistics of Generic Two-Mode Squeezed Coherent Light

for two-mode squeezed coherent states, the photon distribution function is expressed in terms of both four-variable and two-variable Hermite polynomials depending on two squeezing parameters, the relative phase between the two oscillators, their “spatial” orientation, and a four-dimensional shift in phase space of the electromagnetic field oscillator. The oscillations of the photon distribution function are discussed. The Wigner function and Q-function of the generic two-mode squeezed vacuum and squeezed coherent state are calculated explicitly.     

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.     

Completeness Relation of Squeezed States in Squeezing Parametric Space Gained by Virtue of IWOP Technique

Using the newly developed technique of integration within an ordered product of operators, we prove that single-mode (or two-mode) squeezed states span a complete space in squeezing parametric space. The proof is concise and direct, and no further knowledge of SU(1,l) general coherent state theory is needed in our discussion.     

Coordinate-Dependent Two-Mode Squeezing Transformations and the Corresponding Squeezed States

We introduce the coordinate-dependent two-mode squeezing transformations and discuss the properties of the corresponding two-mode squeezed states.     

Nonlinear two-mode squeezing obtained by analysing two-mode exponential quadrature operators in entangled state representation

By analysing the properties of two-mode quadratures in an entangled state representation (ESR) we derive from ESR some complicated exponential quadrature operators for nonlinear two-mode squeezing, which directly leads to wave function of the nonlinear squeezed state in ESR.     

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.     

V型三能级原子双模光场系统中光场压缩性质

本文利用格子液体方法对文献中给出的V型三能级原子玻色-爱因斯坦凝聚体与双模压缩相干态光场相互作用系统的哈密顿量进行分析,发现文献中对原子间相互作用部分的处理有不合理之处,从而对该哈密顿量作出了改进并研究了V型三能级原子双模光场系统中光场压缩性质.结果表明:光场两正交分量交替呈现周期性压缩现象,其压缩深度与光场初始压缩因子密切相关,而压缩时间与双模光场的频率有关. 关键词： 玻色-爱因斯坦凝聚 V型三能级原子 压缩相干态 双模压缩态光场     

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.     

一种双模压缩微波制备的相位锁定方案

相位锁定是双模压缩微波制备的关键问题之一.针对基于超导180°混合环的制备方案相位稳定度不高且信息处理复杂等问题,提出一种相位锁定方案.对约瑟夫森参量放大器的信号输入进行相位调制,输出的单模压缩微波与另一未调制的同频单模压缩微波在超导180°混合环内干涉,实现双模压缩微波的制备与路径分离.将未调制的单模压缩微波与一路双模压缩微波混频,解调出相位调制信号可得到两路单模压缩微波的相对相位及误差,将相位误差反馈于约瑟夫森参量放大器的抽运实现相对相位的锁定,获得稳定的双模压缩输出.本研究对高性能纠缠微波源的设计提供了理论参考.     

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.