arXiv subjects

Xue-xiang Xu

Publications and source records attributed to Xue-xiang Xu.

26 records · Page 2Linked to original sources

arXiv2010

Wigner function evolution in self-Kerr Medium derived by Entangled state representation

By introducing the thermo entangled state representation, we convert the calculation of Wigner function (WF) of density operator to an overlap between "two pure" states in a two-mode enlarged Fock space. Furthermore, we derive a new WF evolution formula of any initial state in self-Kerr Medium with photon loss and find that the photon number distribution for any initial state is independent of the coupling factor with Kerr Medium, where the number state is not affected by the Kerr nonlinearity and evolves into a density operator of binomial distribution.

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arXiv2010

New 3-mode squeezing operator and squeezed vacuum state in 3-wave mixing

In a 3-wave mixing process occurring in some nonlinear optical medium when }$a_{1}^{\dagger}${\small mode interacts with both }$a_{2}^{\dagger}% ${\small mode and }$a_{3}^{\dagger}${\small mode, we theoretically study the squeezing effect generated by the operator }$S_{3}\equiv \exp[μ(a_{1}% a_{2}-a_{1}^{\dagger}a_{2}^{\dagger})+ν(a_{1}a_{3}-a_{1}^{\dagger}% a_{3}^{\dagger})]${\small . The new 3-mode squeezed vacuum state in Fock space is derived, and the uncertainty relation for it is demonstrated, It turns out that }$S_{3}${\small may exhibit enhanced squeezing. By virtue of the technique of integration within an ordered product (IWOP) of operators, we also derive }$S_{3}${\small 's normally ordered expansion. The Wigner function of new 3-mode squeezed vacuum state is calculated by using the Weyl ordering invariance under similar transformations.

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arXiv2010

Entanglement and nonlocality of one- and two-mode combination squeezed state

We investigate the entanglement and nonlocality properties of one- and two-mode combination squeezed vacuum state (OTCSS, with two-parameter lamda and gamma) by analyzing the logarithmic negativity and the Bell's inequality. It is found that this state exhibits larger entanglement than that of the usual two-mode squeezed vacuum state (TSVS), and that in a certain regime of lamda, the violation of Bell's inequality becomes more obvious, which indicates that the nonlocality of OTCSS can be stronger than that of TSVS. As an application of OTCSS, the quantum teleportaion is examined, which shows that there is a region spanned by lamda and gamma in which the fidelity of OTCSS channel is larger than that of TSVS.

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arXiv2010

Photon-subtracted squeezed thermal state: nonclassicality and decoherence

{\small We investigate nonclassical properties of the field states generated by subtracting any number photon from the squeezed thermal state (STS). It is found that the normalization factor of photon-subtracted STS (PSSTS) is a Legendre polynomial of squeezing parameter }${\small r}${\small \ and average photon number }$\bar{n}$ {\small of thermal state. Expressions of several quasi-probability distributions of PSSTS are derived analytically. Furthermore, the nonclassicality is discussed in terms of the negativity of Wigner function (WF). It is shown that the WF of single PSSTS always has negative values if }$\bar{n}<\sinh^{2}r${\small \ at the phase space center. The decoherence effect on PSSTS is then included by analytically deriving the time evolution of WF. The results show that the WF of single PSSTS has negative value if }$2κt<\ln\{1-(2\bar{n}+1)(\bar{n}-\sinh^{2}% r)${\small }$[(2\mathfrak{N}+1)(\bar{n}\cosh2r+\sinh^{2}r)]\}${\small, which is dependent not only on average number }$\mathfrak{N}${\small \ of environment, but also on }$\bar{n}$ {\small and }$r${\small . }

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arXiv2009

Atomic coherent state in Schwinger bosonic realization for optical Raman coherent effect

For optical Raman coherent effect we introduce the atomic coherent state (or the angular momentum coherent state with various angular momemtum values) in Schwinger bosonic realization, they are the eigenvectors of the Hamiltonian describing the Raman effect. Similar to the fact that the photon coherent state describes laser light, the atomic coherent state is related to Raman process.

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arXiv2009

Photon--added squeezed thermal states: statistical properties and its decoherence in a photon-loss channel

Using the normally ordered Gaussian form of displaced-squeezed thermal field characteristic of average photon number n, we introduce the photon-added squeezed thermo state (PASTS) and investigate its statistical properties, such as Mandel's Q-parameter, number distribution (as a Legendre polynomial), the Wigner function. We then study its decoherence in a photon-loss channel in term of the negativity of WF by deriving the analytical expression of WF for PASTS. It is found that the WF with single photon-added is always partial negative for the arbitrary values of n and the squeezing parameter r.

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arXiv2009

Entropy-variation with respect to the resistance in quantized RLC circuit derived by generalized Hellmann-Feynman theorem

By virtue of the generalized Hellmann-Feynman theorem for ensemble average, we obtain internal energy and average energy consumed by the resistance R in a quantized RLC electric circuit. We also calculate entropy-variation with respect to R. The relation between entropy and R is also derived. By depicting figures we indeed see that the entropy increases with the increment of R.

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arXiv2009

New application of Dirac's representation: N-mode squeezing enhanced operator and squeezed state

It is known that exp[i\lamda(Q_1P_1-i/2)] is a unitary single-mode squeezing operator, where Q_1,P_1 are the coordinate and momentum operators, respectively. In this paper we employ Dirac's coordinate representation to prove that the exponential operator S_{n}=Exp[i\lamda sum_{i=1}^{n}](Q_{i}P_{i+1}+Q_{i+1}P_{i}))], (Q_{n+1}=Q_1P_{n+1}=P_1), is a n-mode squeezing operator which enhances the standard squeezing. By virtue of the technique of integration within an ordered product of operators we derive S_{n}'s normally ordered expansion and obtain new n-mode squeezed vacuum states, its Wigner function is calculated by using the Weyl ordering invariance under similar transformations.

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