Splitting the entanglement When particles in a quantum mechanical system are entangled, a measurement performed on one part of the system can affect the results of the same type of measurement performed on another part—even if these subsystems are physically separated. Kunkel et al., Fadel et al., and Lange et al. achieved this so-called distributed entanglement in a particularly challenging setting: an ensemble of many cold atoms (see the Perspective by Cavalcanti). In all three studies, the entanglement was first created within an atomic cloud, which was then allowed to expand. Local measurements on the different, spatially separated parts of the cloud confirmed that the entanglement survived the expansion. Science, this issue p. 413, p. 409, p. 416; see also p. 376 Local measurements on spatially separated parts of a cold atom cloud confirm entanglement between the subsystems. A key resource for distributed quantum-enhanced protocols is entanglement between spatially separated modes. However, the robust generation and detection of entanglement between spatially separated regions of an ultracold atomic system remain a challenge. We used spin mixing in a tightly confined Bose-Einstein condensate to generate an entangled state of indistinguishable particles in a single spatial mode. We show experimentally that this entanglement can be spatially distributed by self-similar expansion of the atomic cloud. We used spatially resolved spin read-out to reveal a particularly strong form of quantum correlations known as Einstein-Podolsky-Rosen (EPR) steering between distinct parts of the expanded cloud. Based on the strength of EPR steering, we constructed a witness, which confirmed genuine 5-partite entanglement.

中文翻译：

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空间分布的多部分纠缠使原子云的 EPR 转向成为可能

分裂纠缠 当量子力学系统中的粒子发生纠缠时，在系统的一个部分执行的测量可能会影响在另一部分执行的相同类型测量的结果——即使这些子系统在物理上是分开的。Kunkel 等人、Fadel 等人和 Lange 等人。在一个特别具有挑战性的环境中实现了这种所谓的分布式纠缠：许多冷原子的集合（参见 Cavalcanti 的观点）。在所有三项研究中，纠缠首先在原子云中产生，然后被允许扩展。对云的不同空间分离部分的局部测量证实，纠缠在膨胀中幸存下来。科学，这个问题 p。413 页。409 页。第416话 另见第。376 对冷原子云空间分离部分的局部测量证实了子系统之间的纠缠。分布式量子增强协议的一个关键资源是空间分离模式之间的纠缠。然而，超冷原子系统空间分离区域之间纠缠的稳健生成和检测仍然是一个挑战。我们在紧密受限的玻色-爱因斯坦凝聚中使用自旋混合，以在单一空间模式中产生无法区分的粒子的纠缠状态。我们通过实验表明，这种纠缠可以通过原子云的自相似膨胀在空间上分布。我们使用空间分辨自旋读数来揭示一种特别强的量子关联形式，称为爱因斯坦-波多尔斯基-罗森 (EPR) 转向在扩展云的不同部分之间。