Characterizing entanglement is central for quantum information science. Special observables which indicate entanglement, so-called entanglement witnesses, are a widely used tool for this task. The construction of these witnesses typically relies on the observation that quantum states with a high fidelity to some entangled target state are entangled, too. We introduce a general method to construct entanglement witnesses based on the Schmidt decomposition of observables. The method works for two-particle and multiparticle systems and is strictly stronger than fidelity-based constructions. The resulting witnesses can also be used to quantify entanglement and to characterize its dimensionality. Finally, we present experimentally relevant examples, where our approach improves entanglement detection significantly.

中文翻译：

---

用算子空间中的施密特分解分析量子纠缠


表征纠缠是量子信息科学的核心。表明纠缠的特殊可观察量，即所谓的纠缠见证，是执行此任务的广泛使用的工具。这些见证的构建通常依赖于对某些纠缠目标态具有高保真度的量子态也发生纠缠的观察。我们介绍了一种基于可观测量的施密特分解来构建纠缠见证的通用方法。该方法适用于双粒子和多粒子系统，并且严格强于基于保真度的构造。由此产生的见证也可用于量化纠缠并表征其维度。最后，我们提出了实验相关的示例，其中我们的方法显着改进了纠缠检测。