Feedback control of quantum entanglement in a two-spin system
Feedback control of quantum entanglement in a two-spin system
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DOI：
10.1016/j.automatica.2006.12.008
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发表时间：
2005-12
期刊：
影响因子：
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通讯作者：
N. Yamamoto;K. Tsumura;S. Hara
中科院分区：
文献类型：
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作者：
N. Yamamoto;K. Tsumura;S. Hara
一对自旋是可以表现出纠缠的最简单的量子系统：在量子信息技术中起着重要作用的非经典特性。研究了以连续测量为条件的对称双自旋系统的反馈控制问题。为了使随机控制理论中一些有用的公式直接适用，我们首先推导了系统的二维表示。然后，我们证明了反馈控制器几乎全局稳定两个自旋的纠缠态，其概率为1。进一步证明了一些与动力学非平衡点对应的纠缠态通过反馈是全局稳定的，即与目标的平均距离可以减小到任意小的值。
A pair of spins is the most simple quantum system that can exhibit entanglement: a nonclassical property that plays an essential role in quantum information technologies. In this paper, feedback control problems of a symmetric two-spin system conditioned on a continuous measurement are investigated. In order to make some useful formulas in stochastic control theory directly applicable, we first derive a two-dimensional representation of the system. We then prove that a feedback controller stabilizes an entangled state of the two spins almost globally with probability one. Furthermore, it is demonstrated that some entangled states, which correspond to nonequilibrium points of the dynamics, are globally stabilized via feedback in the sense that the mean distance from a target can be reduced to an arbitrarily small value.