Entangled Property in Cloned Superposition State

With spin squeezing and quantum Fisher information we investigate the entangled property of the cloned superposition state which is superposed by two states. We first derive the mean spin direction, the optimally squeezed angle and the anti-squeezed angle. Then we numerically calculate the dependence of spin squeezing parameter and the reciprocal of the mean quantum Fisher information on the superposed coefficients and the relative phase. Its shown that the entangled degree is determined by the superposed coefficients and the relative phase.     

Spin Squeezing of a General 3-Qubit State

We investigate the spin squeezing of a general 3-qubit state, which is superposed by a GHZ state and two W states. Numerical solutions for the length of mean spin, mean spin direction and spin squeezing were given. It is shown that the mean spin direction, the length of mean spin and the spin squeezing parameter are determined by the superposition coefficients and the relative phases between the GHZ state and the two W states.     

Spin Squeezing in Multi-Qubit State

We investigate the spin squeezing of a multi-qubit state superposed by four Dicke state. Numerically solutions for optimally squeezed angle and spin squeezing parameter are derived. Optimally squeezed angle and spin squeezing parameter are determined by the superposition coefficients and the relative phase.     

Spin Squeezing of 4-Qubit State

We investigate the spin squeezing of a 4-qubit state, which is superposed by a 4-qubit GHZ state and two W states with a relative phase. Numerically solution for spin squeezing parameter is given. It is shown that the parameter depends on the superposition coefficients and the relative phase. It is shown that spin squeezing exists over a relatively long time with increasing superposition coefficient γ and the smaller the value of relative phase is, the longer the time of existing spin squeezing.     

Spin Squeezing of Superposition

We investigate the mean spin direction, length of mean spin and spin squeezing in a general superposition of a GHZ state and a W state. It is shown that the mean spin direction and spin squeezing parameter are determined by the coefficients of superposition and the relative phase between the GHZ state and the W state; while the length of mean spin is only determined by coefficients of superposition.     

Controlling Spin Squeezing and Quantum Fisher Information with a Strong External Field

We investigate the mean spin direction, length of mean spin and spin squeezing in a general superposition of a GHZ state and a W state. It is shown that the mean spin direction and spin squeezing parameter are determined by the coefficients of superposition and the relative phase between the GHZ state and the W state; while the length of mean spin is only determined by coefficients of superposition.     

Entangled Property of a Multipartite State Superposed by Three Dicke States with Arbitrary Relative Phases

With spin squeezing parameter we investigate the entangled property of a multipartite state superposed by three Dicke states with arbitrary relative phases. We first derive the mean spin direction, the optimally squeezed angle, and then numerically calculate the dependence of spin squeezing parameter on the superposition coefficients, the relative phases and the forms of the Dicke states. It’s shown that the entangled property depends on these parameters.     

Spin Squeezing in 4-Qubit State Superposed by GHZ State, W State and Symmetric State

We investigate the entangled property via spin squeezing in a 4-qubit state superposed by a GHZ state, W state and symmetric state with relative phases. Numerically solutions for spin squeezing parameter are derived. Mean spin direction and the spin squeezing parameters are determined by the superposition coefficients and the relative phases.     

Quantum Fisher Information of Superposition of Many-Body GHZ-Class State and <Emphasis Type="Italic">W</Emphasis> State

We investigate the properties of quantum Fisher information in a general superposition of many-body GHZ-class state and W state. It is shown that mean spin direction is determined by the superposed coefficients and the relative phase between the GHZ-class state and the W state and it is independent of the relative phase between the GHZ-class state; while mean spin length and quantum Fisher information are only determined by the superposed coefficients.     

Spin Squeezing of Superposition of Multi-Qubit GHZ State and W State

We investigate the properties of spin squeezing in a general superposition of multi-qubit GHZ state and W state. It is shown that the mean spin direction is determined by the coefficients of superposition and the relative phase between the GHZ state and the W state; while the length of mean spin and spin squeezing parameter are only determined by coefficient of superposition.     

Spin Squeezing of Arbitrary Superposition of Two Three-Qubit <Emphasis Type="Italic">W</Emphasis> States

We investigate the spin squeezing in a arbitrary superposition of two three-qubit W states. It is shown that the mean spin direction is determined by the superposition coefficients and the relative phase; while the length of mean spin and the spin squeezing parameter are only determined by the superposition coefficients. It is also shown that there is squeezing in the n ₂ direction and there is no squeezing in the n ₁ direction.     

Spin Squeezing of Superposition of Biaxial State and Two Qubit Bell State

In this study we investigate the spin squeezing in superposition of a Biaxial state (Mallesh et al. in J. Phys. A, Math. Gen. 33:779–789, 2000 and Sirsi in Theoretical studies on spin distributions in external electric and magnetic fields, 1995) and Bell state. Numerical and analytical solutions for the length of mean spin, mean spin direction and spin squeezing are given. It is shown that both the mean spin direction and spin squeezing parameter are determined by the coefficients of superposition and the relative phase.     

Spin Squeezing in Superposition of Four-Qubit Symmetric State and W States

We investigate the entanglement property of a four-qubit state superposed by a four-qubit GHZ state and a symmetric state with spin squeezing. Numerically and analytic solutions for spin squeezing parameters are given. The squeezed parameters depend on the superpose coefficients and the relative phases. It is shown that there is no spin squeezing at n ₁ direction and it occurs at n ₂ direction under some conditions.     

Mean spin direction and spin squeezing in superpositions of spin coherent states

We consider the mean spin direction (MSD) of superpositions of two spin coherent states (SCS) | ± μ〉, and superpositions of | μ〉 and | μ*〉 with a relative phase. We find that the azimuthal angle exhibits a π transition for both states when we vary the relative phase. The spin squeezing of the states, and the bosonic counterpart of the mean spin direction are also discussed.      

叠加的奇偶SU(1,1)相干态的统计性质

研究了将两个SU(1,1)相干态｜ζ,k〉和｜ζ,k〉叠加起来得到的新的量子态的统计性质．偶SU(1,1)相干态｜ζ,1/4〉和奇SU(1,1)相干态｜ζ,3/4〉分别对应于压缩真空态和压缩单光子数态．适当选取SU(1,1)态的相位角和叠加时的相对相位,得到的新的量子态比单个SU(1,1)相干态表现出大大增强的正交分量压缩和光子反群聚效应．也说明了怎样准备这样的叠加态． 关键词：     

Spin Squeezing in Superpositions of GHZ State and W States

We investigate the spin squeezing in superpositions of a N-qubit GHZ state and two W states. The spin squeezing parameter is determined by the superposition coefficients and the relative phase. It is shown that there is squeezing in the n ₂ direction and there is no squeezing in the n ₁ direction. It is also shown that the state with more number of qubits has smaller spin squeezing parameter.     

Phase Coherence and Spin Squeezing in One-Axis Twisting Model with Decay

We investigate phase coherence and spin squeezing of a collective spin governed by one-axis twisting Hamiltonian with decay. Here we are interested in the dependence of phase coherence and spin squeezing parameter on the decay. The analytical expressions of phase coherence and spin squeezing parameter are obtained. The stronger decay can induce a stronger spin squeezing, and the squeezing can maintain a longer time interval. Moreover, more squeezing can be achieved by increasing the number of particles.     

Controlling Single-Particle Coherence and Spin Squeezing with Stimulated Raman Transition

We present a scheme for controlling single-particle coherence and spin squeezing of atom-photon with stimulated Raman transition. Here we are focus on the dependence of spin squeezing parameter on the mean photon number. We first derive the effective Hamiltonian and then obtain the analytical solution for state vector, the single-particle coherence and spin squeezing parameter. The stronger spin squeezing can be created by adding the mean photon number.     

Coherent manipulation of spin squeezing in atomic Bose-Einstein condensate via electromagnetically induced transparency

We propose a scheme to coherently control spin squeezing of atomic Bose-Einstein condensate (BEC) via the technique of electromagnetically induced transparency (EIT). We study quantum dynamics of the mean spin vector and spin squeezing. It is shown that the mean spin vector and spin squeezing of the BEC can be controlled and manipulated by adjusting the external coupling fields or/and internal nonlinear interactions of the BEC. It is indicated that the spin squeezing can be generated rapidly in the dynamical process and maintained in a long time interval. It is found that a larger effective Rabi coupling between atoms and lasers can produce a stronger spin squeezing, and the squeezing can maintain a longer time interval.     

The nonclassical properties of the superposition involving two squeezing coherent states

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