We introduce and investigate an open many-body quantum system in which kinetically constrained coherent and dissipative processes compete. The form of the incoherent dissipative dynamics is inspired by that of epidemic spreading or cellular-automaton-based computation related to the density-classification problem. It features two nonfluctuating absorbing states as well as a ${\mathcal{Z}}_2$-symmetric point in parameter space. The coherent evolution is governed by a kinetically constrained ${\mathcal{Z}}_2$-symmetric many-body Hamiltonian which is related to the quantum XOR-Fredrickson-Andersen model. We show that the quantum coherent dynamics can stabilize a fluctuating state and we characterize the transition between this active phase and the absorbing states. We also identify a rather peculiar behavior at the ${\mathcal{Z}}_2$-symmetric point. Here the system approaches the absorbing-state manifold with a dynamics that follows a power law whose exponent continuously varies with the relative strength of the coherent dynamics. Our work shows how the interplay between coherent and dissipative processes as well as symmetry constraints may lead to a highly intricate nonequilibrium evolution and may stabilize phases that are absent in related classical problems.

中文翻译：

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具有两个吸收态的动力学约束开放多体系统中量子稳定脉动相和临界动力学的特征

我们介绍并研究了一个开放的多体量子系统，其中动力学约束的相干和耗散过程相互竞争。非相干耗散动力学的形式受到与密度分类问题相关的流行病传播或基于元胞自动机的计算的启发。它具有两个非波动的吸收状态以及一个${\mathcal{Z}}_2$-参数空间中的对称点。相干演化受动力学约束${\mathcal{Z}}_2$-与量子 XOR-Fredrickson-Andersen 模型相关的对称多体哈密顿量。我们证明了量子相干动力学可以稳定一个波动状态，并且我们描述了这个活跃相和吸收状态之间的转变。我们还发现了一个相当奇特的行为${\mathcal{Z}}_2$-对称点。在这里，系统接近吸收态流形的动力学遵循幂律，其指数随着相干动力学的相对强度而连续变化。我们的工作展示了相干和耗散过程以及对称约束之间的相互作用如何导致高度复杂的非平衡演化，并可能稳定相关经典问题中不存在的相。