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The Berry phase in a composite system induced by the time-dependent interaction is discussed. We choose two coupled spin-1/2 systems as the composite system: one of the subsystems is subjected to a static magnetic field, and the coupling parameters between two spins are controllable in time. We show that the time-dependent interaction can induce the Berry phase in a similar way as that a spin-1/2 system (qubit) is driven by an effective time-dependent magnetic field. Furthermore, using two consecutive cycles with opposite directions of both the static magnetic field as well as opposite signs of the coupling parameters, a nontrivial two-qubit unitary transformation purely based on Berry phases can be constructed. 相似文献
2.
In this paper, we study the entanglement dynamics of two-spin
Heisenberg XYZ model with the Dzialoshinskii--Moriya (DM)
interaction. The system is initially prepared in the Werner state.
The effects of purity of the initial state and DM coupling parameter
on the evolution of entanglement are investigated. The necessary and
sufficient condition for the appearance of the entanglement sudden
death (ESD) phenomenon has been deduced. The result shows that the
ESD always occurs if the initial state is sufficiently impure for
the given coupling parameter or the DM interaction is sufficiently
strong for the given initial state. Moreover, the critical values of
them are calculated. 相似文献
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