论文标题
与反馈的自适应电路中的纠缠转向
Entanglement Steering in Adaptive Circuits with Feedback
论文作者
论文摘要
经过深入研究的测量引起的纠缠相变已成为非自动量子多体动力学的标志。通常，这种过渡仅显示在每个单个量子轨迹的水平上，并且对于测量结果的密度矩阵不存在。在这项工作中，我们引入了一类具有反馈的自适应随机电路模型，这些电路模型在两种情况下都表现出过渡。每次测量之后，都会根据测量结果进行单一操作，要么不使用统一的操作，该结果将平均密度矩阵转向以上唯一的测量阈值的唯一状态。有趣的是，通常以\ textit {不同的}临界测量速率发生了密度矩阵的过渡和单个量子轨迹中的纠缠转变。我们证明了以前的过渡属于均衡的普遍性类，该类别的明确映射到经典的分支宣布随机步行过程中。
The intensely studied measurement-induced entanglement phase transition has become a hallmark of non-unitary quantum many-body dynamics. Usually, such a transition only shows up at the level of each individual quantum trajectory, and is absent for the density matrix averaged over measurement outcomes. In this work, we introduce a class of adaptive random circuit models with feedback that exhibit transitions in both settings. After each measurement, a unitary operation is either applied or not depending on the measurement outcome, which steers the averaged density matrix towards a unique state above a certain measurement threshold. Interestingly, the transition for the density matrix and the entanglement transition in the individual quantum trajectory in general happen at \textit{different} critical measurement rates. We demonstrate that the former transition belongs to the parity-conserving universality class by an explicit mapping to a classical branching-annihilating random walk process.
