论文标题
最大程度地控制在马尔可夫腐蚀的影响下最大化和维持两级系统的叠加状态
Optimal control for maximally creating and maintaining a superposition state of a two-level system under the influence of Markovian decoherence
论文作者
论文摘要
降低的分解是迈向实现当前嘈杂中间尺度量子（NISQ）计算机的通用量子计算机的重要步骤。为此，通常采用将外部磁场应用于Qubits的动力解耦（DD）方法。我们通过使用量子最佳控制理论和略微修改的设置，使用两级模型系统（Qubit）在马尔可夫消融的影响下使用数值研究DD，其中物理目标是在指定的控制周期中最大程度地创建和维持指定的叠加状态。最佳脉冲是在系统地设计的，同时会在系统上改变倾向，种群衰减，脉搏和控制期的值以及使用两种目标函数。尽管由于反应性而引起的纯度下降会导致目标期望值的上限，即饱和值，但最佳形状的脉冲通过逐渐创建目标叠加状态以尽可能地实现饱和值，从而有效地应对逆转。
Reducing decoherence is an essential step toward realizing general-purpose quantum computers beyond the present noisy intermediate-scale quantum (NISQ) computers. To this end, dynamical decoupling (DD) approaches in which external fields are applied to qubits are often adopted. We numerically study DD using a two-level model system (qubit) under the influence of Markovian decoherence by using quantum optimal control theory with slightly modified settings, in which the physical objective is to maximally create and maintain a specified superposition state in a specified control period. An optimal pulse is numerically designed while systematically varying the values of dephasing, population decay, pulse fluence, and control period as well as using two kinds of objective functionals. Although the decrease in purity due to the decoherence gives rise to the upper limit of the target expectation value, i.e., the saturated value, the optimally shaped pulse effectively deals with the decoherence by gradually creating the target superposition state to realize the saturated value as much as possible.
