标题： 相空间测量、退相干和经典性 显示英文标题

标题： Phase-space measurements, decoherence and classicality

摘要： 量子理论中经典行为的出现通常归因于量子系统与其环境的相互作用，这可以被解释为环境对系统的监控。 因此，在一个优选可观测量的基底下，系统的密度矩阵的非对角元素会衰减，导致退相干现象的发生。 这种效应可以通过由位置算符驱动的Lindblad方程进行动态建模。 在此，讨论了环境对位置和动量的监控引起的退相干问题，即相空间测量。 不存在与检测相空间点相对应的标准量子可观测量，这是由海森堡不确定性原理所禁止的。 通过使用基于相干态的正算子值测度（POVM）来模拟环境对相空间的监控，解决了这一问题。 在这个方案中，相空间中的退相干意味着在位置和动量表示下密度矩阵的对角化。 这被证明与一个Lindblad动力学有关，其中位置和动量作为两个独立的Lindblad算符出现。 显示英文摘要

摘要： The emergence of classical behaviour in quantum theory is often ascribed to the interaction of a quantum system with its environment, which can be interpreted as environmental monitoring of the system. As a result, off-diagonal elements of the density matrix of the system are damped in the basis of a preferred observable, often taken to be the position, leading to the phenomenon of decoherence. This effect can be modelled dynamically in terms of a Lindblad equation driven by the position operator. Here the question of decoherence resulting from a monitoring of position and momentum, i.e. a phase-space measurement, by the environment is addressed. There is no standard quantum observable corresponding to the detection of phase-space points, which is forbidden by Heisenberg's uncertainty principle. This issue is addressed by use of a coherent-state-based positive operator-valued measure (POVM) for modelling phase-space monitoring by the environment. In this scheme, decoherence in phase space implies the diagonalisation of the density matrix in both position and momentum representations. This is shown to be linked to a Lindblad dynamics where position and momentum appear as two independent Lindblad operators.