标题： 量子资源在纯化和冷却中的应用：基本限制与机遇 显示英文标题

标题： Quantum resources for purification and cooling: fundamental limits and opportunities

摘要： 在存在环境的情况下，量子系统的纯态制备最终受到系统演化性质以及环境初始状态本身的限制。 我们表明，当系统和环境最初不相关，并且允许任意联合单位动力学时，只有当其环境（自然或设计的）包含一个“虚拟子系统”，该子系统的维度相同且处于期望纯度的状态时，系统才能被纯化到一定（可能任意小）的阈值。 除了提供一种“广义交换过程”来统一理解量子纯化动力学外，我们的结果揭示了关于精确基态冷却的不可能定理的重要性，以及实现预期纯化任务所需的量子资源。 显示英文摘要

摘要： Preparing a quantum system in a pure state is ultimately limited by the nature of the system's evolution in the presence of its environment and by the initial state of the environment itself. We show that, when the system and environment are initially uncorrelated and arbitrary joint unitary dynamics is allowed, the system may be purified up to a certain (possibly arbitrarily small) threshold if and only if its environment, either natural or engineered, contains a "virtual subsystem" which has the same dimension and is in a state with the desired purity. Beside providing a unified understanding of quantum purification dynamics in terms of a "generalized swap process," our results shed light on the significance of a no-go theorem for exact ground-state cooling, as well as on the quantum resources needed for achieving an intended purification task.