Quantum discord for two-qubit systems
Quantum discord for two-qubit systems
复制标题
双量子位系统的量子不一致
DOI：
10.1103/physreva.77.042303
复制
发表时间：
2008-04-01
影响因子：
2.9
通讯作者：
Luo, Shunlong
中科院分区：
文献类型：
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作者：
Luo, Shunlong
量子不和谐，由奥利佛和祖雷克[物理学家]提出。Rev. Lett. 88, 017901(2001)]，是对经典互信息的两个自然但不同的量子类似物之间差异的测量。这一概念从测量的角度表征和量化了二部态中相关的量子化，与纠缠与可分性范式中的各种纠缠度量有着根本的不同。非零量子不和谐现象是由于非对易性而非纠缠引起的量子相关的一种表现，在揭示某些量子任务的优势方面具有有趣而重要的应用。我们将对一个大的双量子位态族的量子不和谐进行分析评价，并在量子不和谐方面对经典相关和量子相关之间的关系进行比较研究。我们进一步将量子不和谐与形成纠缠进行了比较，并说明后者可能大于前者，尽管对于可分态，形成纠缠总是消失，因此小于量子不和谐。
Quantum discord, as introduced by Olliver and Zurek [Phys. Rev. Lett. 88, 017901 (2001)], is a measure of the discrepancy between two natural yet different quantum analogs of the classical mutual information. This notion characterizes and quantifies quantumness of correlations in bipartite states from a measurement perspective, and is fundamentally different from the various entanglement measures in the entanglement vs separability paradigm. The phenomenon of nonzero quantum discord is a manifestation of quantum correlations due to noncommutativity rather than due to entanglement, and has interesting and significant applications in revealing the advantage of certain quantum tasks. We will evaluate analytically the quantum discord for a large family of two-qubit states, and make a comparative study of the relationships between classical and quantum correlations in terms of the quantum discord. We furthermore compare the quantum discord with the entanglement of formation, and illustrate that the latter may be larger than the former, although for separable states, the entanglement of formation always vanishes and thus is less than the quantum discord.