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arXiv quant-ph/0610007quant-ph
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非马尔可夫动力学下两量子比特与公共电磁场相互作用的量子纠缠

Quantum Entanglement under Non-Markovian Dynamics of Two Qubits Interacting with a common Electromagnetic Field

C. Anastopoulos, S. Shresta, B. L. Hu

摘要:

我们研究了由两个原子组成的一对量子比特的非平衡动力学,这些原子在空间中以距离r分开,并与一个共同的电磁场相互作用,但彼此不直接相互作用。我们的计算做了弱耦合假设,但没有玻恩或马尔可夫近似。导出了两量子比特系统在积分出电磁场模式后约化密度矩阵演化的非马尔可夫主方程。它包含一个马尔可夫部分与Lindblad型运营商和nonMarkovian的贡献,其中的物理是本研究的主要重点。我们使用并发函数作为两个量子比特之间的量子纠缠的度量。详细研究了两类态:A类是最高能量叠加的单参数态族,B类是对称和反对称Bell态的线性组合。我们得到类似的行为贝尔状态在早期的结果,通过使用Born-Markov近似。然而,在A类状态中,行为是定性不同的:在非马尔可夫演化下,我们看不到量子纠缠的突然死亡和随后的复活,除非量子比特相距足够远。我们提供的解释,这两类国家之间的行为和预测之间的马尔可夫和非马尔可夫动力学的差异。我们还研究了这种双量子比特系统的退相干,发现当一个量子比特初始处于激发态时,退相干率随量子比特间隔的变化并不显著,而当一个量子比特初始处于基态时,退相干率随量子比特间隔的变化显著.

英文摘要:

We study the non-equilibrium dynamics of a pair of qubits made of two-level atoms separated in space with distance r and interacting with one common electromagnetic field but not directly with each other. Our calculation makes a weak coupling assumption, but no Born or Markov approximation. We derived a non-Markovian master equation for the evolution of the reduced density matrix of the two-qubit system after integrating out the electromagnetic field modes. It contains a Markovian part with a Lindblad type operator and a nonMarkovian contribution, the physics of which is the main focus of this study. We use the concurrence function as a measure of quantum entanglement between the two qubits. Two classes of states are studied in detail: Class A is a one parameter family of states which are the superposition of the highest energy and Class B states are linear combinations of the symmetric and the antisymmetric Bell states. We obtain similar behavior for the Bell states as in earlier results derived by using the Born-Markov approximation. However, in the Class A states the behavior is qualitatively different: under the non-Markovian evolution we do not see sudden death of quantum entanglement and subsequent revivals, except when the qubits are sufficiently far apart. We provide explanations for such differences of behavior both between these two classes of states and between the predictions from the Markov and non-Markovian dynamics. We also study the decoherence of this two-qubit system and find that the decoherence rate in the case of one qubit initially in an excited state does not change significantly with the qubits separation whereas it does for the case when one qubit is initially in the ground state.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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