Robust quantum gates for open systems via optimal control: Markovian versus non-Markovian dynamics
Robust quantum gates for open systems via optimal control: Markovian versus non-Markovian dynamics
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DOI：
10.1088/1367-2630/14/7/073023
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发表时间：
2012-07-11
影响因子：
3.3
通讯作者：
Schirmer, Sophie G.
中科院分区：
文献类型：
--
作者：
Floether, Frederik F.;de Fouquieres, Pierre;Schirmer, Sophie G.
我们研究了一个，两个和三个量子比特量子门的相互作用量子比特使用最优控制的实现。马尔可夫和非马尔可夫环境进行了比较和有效的优化算法，利用解析梯度表达式和拟牛顿更新的情况下。的算法的性能进行了分析，为一个大的问题，在所获得的qualities和所观察到的收敛行为。新的成功率和成功速度的概念被引入和密度图被用来研究关键参数的影响，如门操作时间，和随机变量，如初始字段所需的开始迭代算法。统计分析了最优场的核特征。马尔可夫和非马尔可夫环境中的控制和控制机制的可能性之间的实质性差异被发现。在非马尔可夫的情况下，门的稳定性大大提高时，系统浴耦合的细节被考虑在内，虽然不完善，如场泄漏可能是一个重大的问题。在马尔可夫的情况下，计算时间节省，如果字段被预先优化忽略环境，而包括后者一般不会显着提高门的并行性。
We study the implementation of one-, two- and three-qubit quantum gates for interacting qubits using optimal control. Markovian and non-Markovian environments are compared and efficient optimization algorithms utilizing analytic gradient expressions and quasi-Newton updates are given for both cases. The performance of the algorithms is analysed for a large set of problems in terms of the fidelities attained and the observed convergence behaviour. New notions of success rate and success speed are introduced and density plots are utilized to study the effects of key parameters, such as gate operation times, and random variables such as the initial fields required to start the iterative algorithm. Core characteristics of the optimal fields are analysed statistically. Substantial differences between Markovian and non-Markovian environments in terms of the possibilities for control and the control mechanisms are uncovered. In the non-Markovian case, gate fidelities improve substantially when the details of the system bath coupling are taken into account, although imperfections such as field leakage can be a significant problem. In the Markovian case, computation time is saved if the fields are pre-optimized neglecting the environment, while including the latter generally does not significantly improve gate fidelities.