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arXiv 1003.5153quant-ph
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动力学背景下纠缠、混合和非定域性之间的联系

Connection among entanglement, mixedness and nonlocality in a dynamical context

Laura Mazzola, Bruno Bellomo, Rosario Lo Franco, Giuseppe Compagno

摘要:

我们研究了在一个公共结构库中的两个量子比特系统中纠缠度、混合度和非定域性之间的动力学关系,分别用并发度C、纯度P和Bell函数B的最大值来量化.为此,我们引入了C-P-B参数空间,并分析了在这样的空间中代表系统状态的点的时间演化。纠缠度、混合度和非定域性之间的动力学相互作用强烈依赖于系统的初始状态。对于双激发Bell态,代表点在C-P-B空间中画出一条多分支曲线,我们证明了这些量子数之间的封闭关系并不成立。通过推广纯态C与B之间的关系,给出了混合态三个量子数之间的一个表达式。在这个方程中,我们引入一个量,对于纯态为零,它通常没有关于C、P和B的封闭形式。最后,我们证明了对于一个初始的单激发Bell态,一个封闭的C-P-B关系反而存在,并且系统演化始终保持一个最大纠缠混合态。

英文摘要:

We investigate the dynamical relations among entanglement, mixedness and nonlocality, quantifed by concurrence C, purity P and maximum of Bell function B, respectively, in a system of two qubits in a common structured reservoir. To this aim we introduce the C-P-B parameter space and analyze the time evolution of the point representative of the system state in such a space. The dynamical interplay among entanglement, mixedness and nonlocality strongly depends on the initial state of the system. For a two-excitation Bell state the representative point draws a multi-branch curve in the C-P-B space and we show that a closed relation among these quantifers does not hold. By extending the known relation between C and B for pure states, we give an expression among the three quantifers for mixed states. In this equation we introduce a quantity, vanishing for pure states which has not in general a closed form in terms of C, P and B. Finally we demonstrate that for an initial one-excitation Bell state a closed C-P-B relation instead exists and the system evolves remaining always a maximally entangled mixed state.

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