Necessary and Sufficient Condition for Nonzero Quantum Discord
Necessary and Sufficient Condition for Nonzero Quantum Discord
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DOI：
10.1103/physrevlett.105.190502
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发表时间：
2010-11-02
影响因子：
8.6
通讯作者：
Brukner, Caslav
中科院分区：
文献类型：
--
作者：
Dakic, Borivoje;Vedral, Vlatko;Brukner, Caslav
量子失协表征了量子力学中关联的“非经典性”。它被认为是某些量子通信任务和量子计算模型中存在的关键资源，且其中不包含大量的纠缠。我们得到了任意维度二分态存在非零量子失协的一个充分必要条件。这个条件在实验上很容易实现。基于此，我们提出了一种量化量子失协的几何方法。对于两个量子比特，这导致了量子失协的一个封闭形式的表达式。我们将我们的结果应用于单量子比特确定性量子计算模型，表明量子失协不太可能是其加速的原因。
Quantum discord characterizes "nonclassicality'' of correlations in quantum mechanics. It has been proposed as the key resource present in certain quantum communication tasks and quantum computational models without containing much entanglement. We obtain a necessary and sufficient condition for the existence of nonzero quantum discord for any dimensional bipartite states. This condition is easily experimentally implementable. Based on this, we propose a geometrical way of quantifying quantum discord. For two qubits this results in a closed form of expression for discord. We apply our results to the model of deterministic quantum computation with one qubit, showing that quantum discord is unlikely to be the reason behind its speedup.