平移激发压缩真空态及其性质

引入平移激发压缩真空态D(z)a\+\{+m\}S(r)|0〉,并讨论它的一些基本性质.利用正规 乘积内的积分技术,证明了其完备性.平移激发以后,与压缩真空态相比较,光子数分布 的振荡性质更加显著.与压缩真空态的光子总是聚束的性质不同,在平移参量|z|和激发 数m都较小时,平移激发压缩真空态的光子统计关联可以呈现反聚束效应.计算了它的准 概率分布函数(Q函数和Wigner函数),并讨论了它们对各参量的依赖关系,从Wigner函数可 以清楚地看出该量子态的非经典特性. 关键词：     

双模激发压缩真空态的维格纳函数

利用纠缠态表象下的维格纳(Wigner)算符,构造了双模激发压缩真空态的维格纳函数,并根据该函数在相空间ρ-γ中随参量m,n和r的变化关系,讨论了双模激发压缩真空态的量子干涉特性和压缩效应。结果表明,对于参量m,n不同的取值,双模激发压缩真空态的量子干涉效应的强弱不同;而对于不同的压缩参量r,双模激发压缩真空态呈现出不同程度的压缩效应。最后,根据双模激发压缩真空态的维格纳函数的边缘分布,阐明了此维格纳函数的物理意义。     

激发双模压缩真空态的非经典特性

通过数值计算研究了激发双模压缩真空态a^+mb^+m|ξ>的非经典特性.结果表明:对于a^+mb^+m|ξ>,Cauchy-Schwartz不等式受到破坏;当取适当的压缩参量r(例如0.4～0.7)时,a^+mb^+m|ξ>呈现出正交分量的压缩和光子的亚泊松分布,而且压缩程度和亚泊松特性都随m的增大而有所增强.     

激发压缩真空态的相位概率分布

应用Pegg和Barnett提出的相位算符和相位态理论,研究了激发压缩真空态的相位概率分布特性.数值计算结果表明,激发压缩真空态的相位概率分布主要受到相位参量和压缩参量的调节,相位参量使相位概率分布呈峰值结构,压缩参量的变化将影响相位概率分布的峰值强度,此外激发光子数对相位概率分布也有较大的影响.     

双模压缩数态光场的Wigner函数及其特性

借助纠缠态表象及Wigner算符在该表象下的表示,得到双模压缩数态的Wigner函数,数值计算画出相空间中Wigner函数的分布图,并加以分析,发现双模压缩数态两模之间相互关联、相互纠缠,对相空间中Wigner函数分布产生影响. 关键词： 双模压缩数态 Wigner函数 纠缠态表象     

叠加激发双模压缩真空态的量子统计特性(英文)

从激发双模压缩真空态a^+mb^+m|ξ>出发构造了叠加态|Ψ>,研究了|Ψ>的量子统计特性.结果表明:在一定的条件下,随着相位差的变化,叠加态|Ψ>的平均光子数出现类似于Rabi振荡的崩塌与复原现象,而且与单个激发双模压缩真空态a^+mb^+m|ξ>相比,在叠加态|Ψ>中光场的相位压缩和亚泊松光子统计特性都得到了加强.     

用纠缠态表象讨论对双模压缩真空态作正交振幅分量的测量

对文献[4]的结果作了进一步推导,用纠缠态表象方法计算了对双模压缩真空态第一个模场作正交振幅分量测量的结果,发现第二个模塌缩到一个压缩态,其显式被导出。     

光子扣除(增加)压缩真空态与压缩猫态的保真度

解析推导了任意光子扣除(增加)压缩真空态与压缩猫态的保真度. 研究表明,无论是光子增加还是光子扣除,最大保真度都随光子增加或扣除数目的增加而增加,且最大保真度对应的叠加态振幅也增加;此外,对于相同数目的增加和扣除光子数,光子增加后的最大保真度所对应的叠加态振幅比光子扣除所对应的叠加态振幅要大,而最大保真度略小一些. 尽管目前从实验上实现光子增加比光子扣除困难较大,但光子增加也可以成为获得大振幅猫态的一个有力手段. 关键词： 光子扣除压缩真空态 光子增加压缩真空态 压缩猫态 保真度     

单、双洞态镁离子的退激发及末电离态离子分布的研究

在分析双洞相关退激发对双洞态退激发的贡献较小的基础上，依据辐射-俄歇-双俄歇级联退激发模型(RACDA)研究了Mg¹⁺(1s^-1)（K壳层单洞态镁离子）和Mg²⁺(1s^-2)（K壳层双洞态镁离子）的退激发过程，计算了它们的末电离态离子的分布，并与辐射-俄歇级联退激发模型的结果进行了比较.RACDA模型计算的Mg¹⁺(1s^-1)的4价末电离态离子的相对丰度较大，而辐射-俄歇级联退激发模型(RAC)的结果中就没有出现4价离子；两种模型计算Mg²⁺(1s^-2)的6价末电离态离子的丰度非常大，而RAC模型下的Mg²⁺(1s^-2)退激发后不产生6价离子. 关键词： 双洞态退激发 RACDA退激发模型     

压缩真空态与两原子相互作用过程中场的压缩性质

本文研究了两个二能级原子通过双光子跃迁与压缩真空态相互作用过程中辐射场的压缩和振幅平方压缩效应,讨论了两个二能级原子与光场的耦合常数的相对大小对它们的影响。     

Decoherence of photon-subtracted squeezed vacuum state in dissipative channel

This paper investigates the decoherence of photo-subtracted squeezed vacuum state (PSSVS) in dissipative channel by describing its statistical properties with time evolution such as Wigner function,Husimi function,and tomogram.It first calculates the normalization factor of PSSVS related to Legendre polynomial.After deriving the normally ordered density operator of PSSVS in dissipative channel,one obtains the explicit analytical expressions of time evolution of PSSVS’s statistical distribution function.It finds that these statistical distributions loss their non-Gaussian nature and become Gaussian at last in the dissipative environment as expected.     

Evolution of a two-mode squeezed vacuum for amplitude decay via continuous-variable entangled state approach

Extending the recent work completed by Fan et al. [Front. Phys. 9(1), 74 (2014)] to a two-mode case, we investigate how a two-mode squeezed vacuum evolves when it undergoes a two-mode amplitude dissipative channel, with the same decay rate κ, using the continuous-variable entangled state approach. Our analytical results show that the initial pure-squeezed vacuum state evolves into a definite mixed state with entanglement and squeezing, decaying over time as a result of amplitude decay. We also investigate the time evolutions of the photon number distribution, the Wigner function, and the optical tomogram in this channel. Our results indicate that the evolved photon number distribution is related to Jacobi polynomials, the Wigner function has a standard Gaussian distribution (corresponding to the vacuum) at long periods, losing its nonclassicality due to amplitude decay, and a larger squeezing leads to a longer decay time.     

Evolution of the single-mode squeezed vacuum state in amplitude dissipative channel

Using the way of deriving infinitive sum representation of density operator as a solution to the master equation describing the amplitude dissipative channel by virtue of the entangled state representation, we show manifestly how the initial density operator of a single-mode squeezed vacuum state evolves into a definite mixed state which turns out to be a squeezed chaotic state with decreasing-squeezing and deeoherence. We investigate average photon number, photon statistics distributions for this mixed state.     

New Approach for Calculating Tomograms of Quantum States by Virtue of the IWOP Technique

We show that for tomographic approach there exist two mutual conjugate quantum states [p,σ, τ） and [x,μ, ν） （named the intermediate coordinate-momentum representation）, and the two Radon transforms of the Wigner operator are just the pure-state density matrices [p）σ1τσ1τ （p｜ and （p）λ,ν,λ,ν,（x｜ respectively. As a result, the tomogram of quantum states can be considered as the module-square of the states＇ wave function in these two representations. Throughout the paper we fully employ the technique of integration within an ordered product of operators. In this way we establish a new convenient formalism of quantum tomogram.     

双模压缩真空态和纠缠相干态的一维势垒散射

分析了双模压缩真空态和纠缠相干态的一维势垒散射问题,结果表明,两种散射态的纠缠度都随势垒的透射系数呈类抛物线关系,且抛物线谷底对应半反半透势垒.前者的纠缠度还随入射压缩因子呈类抛物线关系,后者随入射纠缠呈线性关系.两种散射的保真度都可以由透射系数的增加而得到提高,但前者还会随入射压缩因子的增大而降低,后者随入射相干态模的增加而降低.     

压缩偶相干态的制备及其非经典特性

通过保持非耗散介观LC电路的固有频率不变，而使电路参数作阶跃函数变化，就可将介观LC电路由初始的偶相干态制备到压缩偶相干态；在压缩偶相干态下，介观电路系统不仅有非经典的量子压缩效应，而且有非经典的反聚束效应. 关键词： 介观LC电路 单位阶跃函数 压缩算符 压缩偶相干态     

Super-sensitivity measurement of tiny Doppler frequency shifts based on parametric amplification and squeezed vacuum state

The precision measurement of Doppler frequency shifts is of great significance for improving the precision of speed measurement. This paper proposes a precision measurement scheme of tiny Doppler shifts by a parametric amplification process and squeezed vacuum state. This scheme takes a parametric amplification process and squeezed vacuum state into a detection system, so that the measurement precision of tiny Doppler shifts can exceed the Cram′er–Rao bound of coherent light. Simultaneously, a simulation study is carried out on the theoretical basis, and the following results are obtained: for the signal light of Gaussian mode, when the amplification factor g = 1 and the squeezed factor r = 0.5, the measurement error of Doppler frequency shifts is 14.4% of the Cramer–Rao bound of the coherent light in our system. At the same time,when the local light mode and squeezed vacuum state mode are optimized, the measurement precision of this scheme can be further improved by ■ times, where n is the mode-order of the signal light.     

Analytical investigation on interactions among squeezed vacuum and coherent state,coherent vacuum and squeezed state,and among phase squeezed and amplitude squeezed states of light

Squeezed state of light has drawn an enormous attention in information processing and digital communication since it has broken the quantum limit of noise. Here we have analytically investigated the interactions among coherent and vacuum squeezed states of light, interaction among coherent vacuum and squeezed states of light, and that between phase and amplitude squeezed states of light signals. Hence we established the nature of the resulting interaction with the help of photon statistics.