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arXiv quant-ph/0608121quant-ph
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一般双模连续变量态中的纠缠:局域方法和到双量子比特系统的映射

Entanglement in general two-mode continuous-variable states: local approach and mapping to a two-qubit system

H. -C. Lin, A. J. Fisher

摘要:

提出了一种新的方法来分析光滑二体连续变量态的纠缠。一方或双方通过初步测量进行投影过滤,以确定系统是否位于空间的某个区域;我们研究过滤后剩余的纠缠。对于小区域,双模系统可以近似为一对量子比特,其纠缠完全表征,即使是混合态。我们的方法可以扩展到任何光滑的二分纯态或双模混合态,导致自然的定义的并发和负密度。对于高斯态,这两个量在整个位形空间中都是常数。

英文摘要:

We present a new approach to the analysis of entanglement in smooth bipartite continuous-variable states. One or both parties perform projective filterings via preliminary measurements to determine whether the system is located in some region of space; we study the entanglement remaining after filtering. For small regions, a two-mode system can be approximated by a pair of qubits and its entanglement fully characterized, even for mixed states. Our approach may be extended to any smooth bipartite pure state or two-mode mixed state, leading to natural definitions of concurrence and negativity densities. For Gaussian states both these quantities are constant throughout configuration space.

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