Open quantum systems as modeled by quantum channels and quantum Markov semigroups usually decay to subspaces that are invariant under environmental interactions. It is known that finite-dimensional semigroups with detailed balance decay exponentially under modified logarithmic-Sobolev inequalities (MLSIs). Here we analyze discrete and continuous processes that include unitary components, breaking the detailed balance assumption. We find counter-examples to analogs of MLSIs for these systems. The generalized quantum Zeno effect appears for many Lindbladians that combine a decay process with unitary drift. As incompatible long-time and Zeno limits compete, strong noise often protects subsystems and subspaces from its own spread. We observe this interplay between decay and Zeno-like effects experimentally on superconducting qubits using IBM Q devices. Nonetheless, by combining MLSIs for effective self-adjoint decay processes across different times, we obtain eventual exponential decay. We similarly obtain decay rate lower bounds for discrete compositions of quantum channels.
翻译:以量子信道和量子Markov 半组为模型的开放量子系统通常会衰落到环境相互作用下无变化的子空间。已知在修改对数-Soblev不平等(MLSIs)下,具有详细平衡的有限维度半组会迅速衰变。在这里,我们分析了包括单元部件的离散和连续过程,打破了详细的平衡假设。我们发现这些系统的MLSI类比的反样。对于将衰变过程与单一漂移相结合的许多林德布拉迪斯人来说,普遍量子Zeno效应会显现出来。随着不相容的长期和Zeno限制的竞争,强噪声往往保护次子和子空间不受自身扩散的影响。我们观察了衰变和Zeno类似作用对使用IBM Q 设备进行超导的Qbit的实验性反应。然而,通过将MLSI结合不同时间的有效自联衰变过程,我们最终会获得指数衰变。我们同样会获得离量通道的衰变率较低界限。