Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
Nature. 2015 Dec 3;528(7580):77-83. doi: 10.1038/nature15750.
Entanglement is one of the most intriguing features of quantum mechanics. It describes non-local correlations between quantum objects, and is at the heart of quantum information sciences. Entanglement is now being studied in diverse fields ranging from condensed matter to quantum gravity. However, measuring entanglement remains a challenge. This is especially so in systems of interacting delocalized particles, for which a direct experimental measurement of spatial entanglement has been elusive. Here, we measure entanglement in such a system of itinerant particles using quantum interference of many-body twins. Making use of our single-site-resolved control of ultracold bosonic atoms in optical lattices, we prepare two identical copies of a many-body state and interfere them. This enables us to directly measure quantum purity, Rényi entanglement entropy, and mutual information. These experiments pave the way for using entanglement to characterize quantum phases and dynamics of strongly correlated many-body systems.
纠缠是量子力学最引人入胜的特性之一。它描述了量子物体之间的非局域相关性，是量子信息科学的核心。纠缠现在正在从凝聚态物质到量子引力等多个领域进行研究。然而，测量纠缠仍然是一个挑战。对于相互作用的非定域粒子系统来说尤其如此，因为对于这种系统，对空间纠缠的直接实验测量一直难以实现。在这里，我们使用多体双胞胎的量子干涉来测量这种巡游粒子系统中的纠缠。利用我们在光学晶格中对超冷玻色原子的单点分辨控制，我们制备了两个相同的多体态副本并对它们进行干涉。这使我们能够直接测量量子纯度、Renyi 纠缠熵和互信息。这些实验为利用纠缠来表征强关联多体系统的量子相和动力学铺平了道路。
