Carollo Federico, Pérez-Espigares Carlos
Institut für Theoretische Physik, Universität Tübingen, Auf der Morgenstelle 14, 72076 Tübingen, Germany.
Departamento de Electromagnetismo y Física de la Materia, Universidad de Granada, Granada 18071, Spain.
Phys Rev E. 2020 Sep;102(3-1):030104. doi: 10.1103/PhysRevE.102.030104.
Controlling dynamical fluctuations in open quantum systems is essential both for our comprehension of quantum nonequilibrium behavior and for its possible application in near-term quantum technologies. However, understanding these fluctuations is extremely challenging due, to a large extent, to a lack of efficient important sampling methods for quantum systems. Here, we devise a unified framework-based on population-dynamics methods-for the evaluation of the full probability distribution of generic time-integrated observables in Markovian quantum jump processes. These include quantities carrying information about genuine quantum features, such as quantum superposition or entanglement, not accessible with existing numerical techniques. The algorithm we propose provides dynamical free-energy and entropy functionals which, akin to their equilibrium counterpart, permit one to unveil intriguing phase-transition behavior in quantum trajectories. We discuss some applications and further disclose coexistence and hysteresis, between a highly entangled phase and a low entangled one, in large fluctuations of a strongly interacting few-body system.
控制开放量子系统中的动力学涨落，对于我们理解量子非平衡行为及其在近期量子技术中的潜在应用都至关重要。然而，很大程度上由于缺乏适用于量子系统的高效重要性抽样方法，理解这些涨落极具挑战性。在此，我们基于种群动力学方法设计了一个统一框架，用于评估马尔可夫量子跳跃过程中一般时间积分可观测量的全概率分布。这些可观测量包括携带有关真正量子特征（如量子叠加或纠缠）信息的量，而现有数值技术无法获取这些信息。我们提出的算法提供了动力学自由能和熵泛函，类似于它们的平衡对应物，使人们能够揭示量子轨迹中有趣的相变行为。我们讨论了一些应用，并进一步揭示了在强相互作用少体系统的大涨落中，高纠缠相和低纠缠相之间的共存和滞后现象。
