We consider topological protection mechanisms in dissipative quantum systems in the presence of quenched disorder, with the intent to prolong the coherence time of a fiducial qubit. The qubit is part of a network of other qubits and dissipative cavities whose coupling parameters are tunable, such that topological edge states can be stabilized. The evolution of the fiducial qubit is entirely determined by a non-Hermitian Hamiltonian which thus emerges from a bona fide physical process. Even in the presence of disorder, a winding number $W$ can be defined and evaluated in real space, as long as certain symmetries are preserved. Hence we can construct the topological phase diagrams of noisy open quantum models, such as the non-Hermitian disordered Su-Schrieffer-Heeger dimer model and a trimer model that includes longer-range couplings. For finite-size systems we find that there are precisely $W$ modes localized at one end of the chain. In such topological phases the qubit's coherence lifetime is exponentially large in the system size. In the presence of competing disorder parameters, interesting reentrance phenomena of topologically nontrivial sectors are observed. This means that in certain parameter regions, increasing disorder drastically increases the coherence time of the fiducial qubit.

中文翻译：

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无序开放量子系统相干性的拓扑保护

我们考虑了存在猝灭无序的耗散量子系统中的拓扑保护机制，目的是延长基准量子位的相干时间。量子位是其他量子位和耗散腔网络的一部分，其耦合参数可调，从而可以稳定拓扑边缘状态。基准量子位的演化完全由非厄米哈密顿量决定，因此它是从真正的物理过程中产生的。即使在无序的情况下，一个绕数$宽$只要保留某些对称性，就可以在真实空间中定义和评估。因此，我们可以构建噪声开放量子模型的拓扑相图，例如非 Hermitian 无序 Su-Schrieffer-Heeger 二聚体模型和包含更远距离耦合的三聚体模型。对于有限大小的系统，我们发现有精确的$宽$模式定位在链的一端。在这样的拓扑阶段，量子位的相干寿命在系统规模中呈指数级增长。在存在竞争性无序参数的情况下，观察到拓扑非平凡扇区的有趣重入现象。这意味着在某些参数区域，增加无序会大大增加基准量子位的相干时间。