Locally optimal measurement-based quantum feedback with application to multiqubit entanglement generation
Locally optimal measurement-based quantum feedback with application to multiqubit entanglement generation
复制标题
基于局部最优测量的量子反馈及其应用于多量子位纠缠生成
作者：
Song Zhang;Leigh S. Martin;K. B. Whaley
我们提出了一种基于测量的量子反馈的一般方法，该方法采用比例和基于量子态（PaQS）的反馈组件来获得局部最优协议。为了证明该方法的力量，我们首先表明，它再现了许多已知的反馈协议，然后将其应用于生成多体纠缠，重点是远程纠缠，这需要空间本地反馈哈密顿量。测量和反馈算子的对称性是构建有效协议的关键。结果表明，在理想的测量效率下，在非马尔可夫反馈控制方案下，纠缠态的保真度接近于1，而通过对系综平均态的反馈幺正进行优化而得到的马尔可夫方案，纠缠态的保真度仍在94%以上.将PaQS方法应用于N比特W态、一般迪凯态和GHZ态的产生，结果表明，在某些情况下，N = 100时，这种纠缠态的产生具有很高的保真度.
We present a general approach to measurement-based quantum feedback that employs proportional and quantum state-based (PaQS) feedback components to obtain locally optimal protocols. To demonstrate the power of the method, we first show that it reproduces many known feedback protocols, and then apply it to generation of multipartite entanglement with an emphasis on remote entanglement, which requires spatially local feedback Hamiltonians. The symmetry of both measurement and feedback operators is found to be essential for construction of effective protocols. We show that under perfect measurement efficiency, entangled states can be reached with fidelity approaching unity under non-Markovian feedback control protocols, while Markovian protocols resulting from optimizing the feedback unitaries on ensemble averaged states still yield fidelities above 94%. Application of the PaQS approach to generation of N-qubit W, general Dicke and GHZ states shows that such entangled states can be efficiently generated with high fidelity, for up to N = 100 in some cases.