In this paper,we have investigated the effect of Calogero-Moser type interaction on the quantum discord of thermal states of a spin chain.Our results imply that the quantum discord depends on the relative distance between the spins,the external magnetic field,and the temperature.By a comparison between the quantum discord and the entanglement of formation,the quantum discord is more robust than the entanglement of formation in the sense that the latter takes a zero value in a large range of the parameters,while the former takes a nonzero value.
The entanglement dynamics of a two-qutrit system under decoherence from a spin environment is investigated by using negativityas entanglement measure. Our results imply that the entanglement evolution depends not only on the coupling strength and thetunneling elements of the environment but also on the number of the freedom degrees and the initial state of the environment.
The second-harmonic generation （SHG） coefficient in an asymmetric quantum dot （QD） with a static magnetic field is theoretically investigated. Within the framework of the effective-mass approximation, we obtain the confined wave functions and energies of electrons in the QD. We also obtain the SHC coefficient by the compact-density-matrix approach and the iterative method. The numerical results for the typical GaAs/AlGaAs QD show that the SHC coefficient depends strongly on the magnitude of magnetic field, parameters of the asymmetric potential and the radius of the QD. The resonant peak shifts with the magnetic field or the radius of the QD changing.
For two unequal-mass particles,we construct the entangled state representation and then derive the corresponding squeezing operator.This squeezing operator has a natural realization in the entangled state representation,which exhibits the intrinsic relation between squeezing and quantum entanglement.This squeezing operator involves both two-mode squeezing and the direct product of two single-mode squeezings.The maximum squeezing occurs when the two particles possess equal mass.When the two particles＇ mass difference becomes large,the component of the two single-mode squeezings becomes dominant.
We study the dynamics of correlations for a hybrid qubit-qutrit system in an XY spin-chain environment with Dzyaloshinsky-Moriya interaction. Our discussion involves a comparative analysis of negativity, quantum discord, and measurement-induced disturbance. It is found that the quantum discord is optimal of the three quantum correlations to de- tect the critical point of quantum phase transition. Only when the qubit interacts with the environment, is the phenomenon of sudden transition between the classical correlation and the quantum discord observed. Moreover, the Dzyaloshinsky- Moriya interaction enhances the decay of quantum correlations.
The effect of Dzialoshiski-Moriya (DM) interaction on the violation of Bell inequality for thermal states of interacting qubits via a two-qubit XXZ spin chain is investigated.Our results imply that the DM interaction and anisotropy taking a large positive value can enhance the Bell violation and improve the threshold temperatures of it.By the comparison between the Bell violation and thermal entanglement,we find that the threshold temperatures of thermal entanglement are higher than those of the Bell violation.This implies that some states are entangled but the Bell inequality is not violated.
MA XiaoSan 1 & WANG AnMin 2 1 School of Electric Engineering and Information,Anhui University of Technology,Maanshan 243002,China
