Dissipation of a two-mode squeezed vacuum state in the single-mode amplitude damping channel

We explore how a two-mode squeezed vacuum state sechθ e^{a+b+ tanh θ} |00> evolves when it undergoes a singlemode amplitude dissipative channel with rate of decay κ. We find that in this process not only the squeezing parameter decreases, tanh θ → e^-κt tanh θ, but also the second-mode vacuum state evolves into a chaotic state exp{b⁺bln[1 - e^-2κt tanh² θ]}. The outcome state is no more a pure state, but an entangled mixed state.     

Dissipation of a two-mode squeezed vacuum state in the single-mode amplitude damping channel

We explore how a two-mode squeezed vacuum state sechθ e^{a+b+ tanh θ} |00> evolves when it undergoes a singlemode amplitude dissipative channel with rate of decay κ. We find that in this process not only the squeezing parameter decreases, tanh θ → e^-κt tanh θ, but also the second-mode vacuum state evolves into a chaotic state exp{b⁺bln[1 - e^-2κt tanh² θ]}. The outcome state is no more a pure state, but an entangled mixed state.     

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     

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.     

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.     

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.     

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.     

Single-mode photon number measurement for the squeezed two-mode number state

Based on the fact that a two-mode squeezed number state is a two-variable Hermite polynomial excitation of the two-mode squeezed vacuum state, the result of one-mode l-photon measurement for the two-mode squeezed number state $S_2|m,n\rangle$ is discussed. It is found that a remaining field-mode simultaneously collapses into a number state $|n-m+l\rangle$ with the coefficient being a Jacobi polynomial of n, m and l, which manifestly exhibits the entanglement between the two modes, i.e. it depends on the number-difference between the two modes. The second mode collapses into an excited coherent state when the first mode is measured as a coherent state.     

退激发压缩真空态及其特性

利用退激发压缩真空态归一化函数的产生函数, 获得了归一化的退激发压缩真空态. 借助于此态的归一化常数和中介表象理论, 我们得到了退激发压缩真空态的量子Tomogram函数和一些新的数学公式.     

Photon-number distribution of two-mode squeezed thermal states by entangled state representation

Using the entangled state representation, we convert a two-mode squeezed number state to a Hermite polynomial excited squeezed vacuum state. We first analytically derive the photon number distribution of the two-mode squeezed thermal states. It is found that it is a Jacobi polynomial; a remarkable result. This result can be directly applied to obtaining the photon number distribution of non-Gaussian states generated by subtracting from (adding to) two-mode squeezed thermal states.     

Two-Mode Excited Squeezed Vacuum State and Its Properties

In this paper, the two-mode excited squeezed vacuum state (TESVS) is studied by using the statistical method. By calculating the normalization of the TESVS, a new form of Jacobi polynomials and some new identities are obtained. The photon number distribution of the TESVS is given and it is a simple form of Jacobi polynomials. Using the entangled state representation of Wigner operator, the Wigner function of the TESVS is obtainded and the variations of the Wigner function with the parameters m, n, and r are discussed. Here from the phase space point of view the TESVS can be well interpreted and described.     

Evolution of a two-mode squeezed vacuum in the amplitude dissipative channel

For the first time we derive the dissipating result of an initial two-mode squeezed pure vacuum state passing through a two-mode amplitude dissipative channel described by the direct product of two independent single-mode master equations. Although these two master equations do not mix the two modes (there is no coupling between them), since the two-mode squeezed state is simultaneously an entangled state, the final state which emerges from passing this channel is a two-mode mixed density operator. The compact expression of the outcoming state is obtained, which manifestly shows that as time evolves, the squeezing effect decreases.     

Evolution of a two-mode squeezed vacuum in the amplitude dissipative channel

For the first time we derive the dissipating result of an initial two-mode squeezed pure vacuum state passing through a two-mode amplitude dissipative channel described by the direct product of two independent single-mode master equations. Although these two master equations do not mix the two modes (there is no coupling between them), since the two-mode squeezed state is simultaneously an entangled state, the final state which emerges from passing this channel is a two-mode mixed density operator. The compact expression of the outcoming state is obtained, which manifestly shows that as time evolves, the squeezing effect decreases.     

function for the squeezed atomic coherent state in entangled state representation and some of its applications

Based on the Einstein, Podolsky, and Rosen (EPR) entangled state representation, this paper introduces the wave function for the squeezed atomic coherent state (SACS), which turns out to be just proportional to a single-variable ordinary Hermite polynomial of order 2j. As important applications of the wave function, the Wigner function of the SACS and its marginal distribution are obtained and the eigenproblems of some Hamiltonians for the generalized angular momentum system are solved.     

Scheme for generating a cluster-type entangled squeezed vacuum state via cavity QED

A scheme is proposed to generate an N-qubit cluster-type entangled squeezed vacuum state （CTESVS） based on the two-photon interaction between a two-level atomand the cavity fields with the cavity QED system. The CTESVS in N separate cavities can be effectively obtained after performing a simple one-qubit measurement on the atom. The influence of cavity decay on the CTESVS is also discussed.     

Super-resolution and super-sensitivity of entangled squeezed vacuum state using optimal detection strategy

Interference metrology is a method for achieving high precision detection by phase estimation. The phase sensitivity of a traditional interferometer is subject to the standard quantum limit, while its resolution is constrained by the Rayleigh diffraction limit. The resolution and sensitivity of phase measurement can be enhanced by using quantum metrology. We propose a quantum interference metrology scheme using the entangled squeezed vacuum state, which is obtained using the magic beam splitter, expressed as |ψ〉=(|ξ〉|0〉+|0〉|ξ〉)/(2+2/coshr)~(1/2), such as the N00 N state. We derive the phase sensitivity and the resolution of the system with Z detection, project detection, and parity detection. By simulation and analysis, we determine that parity detection is an optimal detection method, which can break through the Rayleigh diffraction limit and the standard quantum limit.     

利用双模压缩真空态实现量子态的远程传输

借助于双模压缩真空态在EPR纠缠态表象中的表示，研究了用双模压缩真空态作为量子通道 实现任意的单模和双模量子态的远程传输. 关键词： 量子隐形传态 EPR纠缠态 压缩真空态     

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     

Quantum metrology with two-mode squeezed thermal state: Parity detection and phase sensitivity

Based on the Wigner-function method, we investigate the parity detection and phase sensitivity in a Mach–Zehnder interferometer(MZI) with two-mode squeezed thermal state(TMSTS). Using the classical transformation relation of the MZI, we derive the input–output Wigner functions and then obtain the explicit expressions of parity and phase sensitivity.The results from the numerical calculation show that supersensitivity can be reached only if the input TMSTS have a large number photons.     

Quantum teleportation of entangled squeezed vacuum states

An optical scheme for probabilistic teleporting entangled squeezed vacuum states (SVS) is proposed. In this scheme, the teieported state is a bipartite entangled SVS, and the quantum channel is a tripartite entangled SVS. The process of the teleportation is achieved by using a 50/50 symmetric beamsplitter and photon detectors with the help of classical information.