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arXiv 2103.13400quant-phgr-qchep-th
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弱耦合局域粒子探测器不能捕获纠缠

Weakly coupled local particle detectors cannot harvest entanglement

Maximilian H. Ruep

摘要:

平坦时空和弯曲时空中的线性实标量量子场的许多态(特别是Reeh-Schlieder态)都纠缠在类空分离的可观测局部代数上。有人认为,这种纠缠可以通过一对所谓的粒子探测器来“收获”,例如奇异或非局部耦合的量子力学谐振子Unruh探测器。为了避免这种不完美的耦合,我们分析了一个独立于模型的本地和协变纠缠收获协议的基础上最近提出的量子场测量理论的本地探针。然后,我们介绍了一个本地粒子探测器的概念,具体给出了一个本地模式的线性实标量探测场可能弯曲的时空和可能的影响下的外部字段。在非微扰分析中,我们发现当探测场初始制备在准自由Reeh-Schlieder态,并与制备在准自由态的系统场耦合时,局域粒子探测器在临界耦合强度以下不能捕获纠缠.这是Reeh-Schlieder状态限制在任何局部模式上的真正混合状态的事实的结果。

英文摘要:

Many states of linear real scalar quantum fields (in particular Reeh-Schlieder states) on flat as well as curved spacetime are entangled on spacelike separated local algebras of observables. It has been argued that this entanglement can be "harvested" by a pair of so-called particle detectors, for example singularly or non-locally coupled quantum mechanical harmonic oscillator Unruh detectors. In an attempt to avoid such imperfect coupling, we analyse a model-independent local and covariant entanglement harvesting protocol based on the local probes of a recently proposed measurement theory of quantum fields. We then introduce the notion of a local particle detector concretely given by a local mode of a linear real scalar probe field on possibly curved spacetime and possibly under the influence of external fields. In a non-perturbative analysis we find that local particle detectors cannot harvest entanglement below a critical coupling strength when the corresponding probe fields are initially prepared in quasi-free Reeh-Schlieder states and are coupled to a system field prepared in a quasi-free state. This is a consequence of the fact that Reeh-Schlieder states restrict to truly mixed states on any local mode.

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