Entanglement witness derived from NMR superdense coding
Entanglement witness derived from NMR superdense coding
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DOI：
10.1088/0305-4470/39/9/011
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发表时间：
2004-05
期刊：
影响因子：
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通讯作者：
R. Rahimi;K. Takeda;M. Ozawa;M. Kitagawa
中科院分区：
文献类型：
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作者：
R. Rahimi;K. Takeda;M. Ozawa;M. Kitagawa
结果表明，仅当核自旋极化超过一定阈值时，通过核磁共振（NMR）进行的超密集编码（SDC）实验才能显示出相对于经典通信的非经典效率增益，并且该阈值与密度矩阵不可分离性的阈值一致。据称，在之前的低核自旋极化核磁共振SDC实验中，由单个量子位介导的两位信息的传递并不归因于纠缠引起的非经典效应，而仅仅是具有大量分子的系综系统中的统计效应。针对纠缠的实验检测，提出了一类新的纠缠见证，它基于贝尔基中核自旋磁化强度的测量，适用于实际的核磁共振实验。
It is shown that superdense coding (SDC) experiments by means of nuclear magnetic resonance (NMR) can show non-classical efficiency gain over classical communication only for nuclear spin polarization beyond a certain threshold, and this threshold coincides with that for non-separability of the density matrix. It is also claimed that transfer of two-bit information mediated by a single qubit in the previous NMR SDC experiments with low nuclear spin polarization is not ascribed to the non-classical effect induced by entanglement, but merely to a statistical effect in an ensemble system having a large number of molecules. Towards experimental detection of entanglement, a new class of entanglement witnesses is proposed, which is based on the measurement of nuclear spin magnetizations in the Bell basis and is suitable for actual NMR experiments.