Kirchhoff-Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany.
Science. 2018 Apr 27;360(6387):413-416. doi: 10.1126/science.aao2254.
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.
一种用于分布式量子增强协议的关键资源是空间分离模式之间的纠缠。然而，在超冷原子系统的空间分离区域中稳健地生成和检测纠缠仍然是一个挑战。我们使用自旋混合在紧密限制的玻色-爱因斯坦凝聚体中生成单空间模式中不可区分粒子的纠缠态。我们通过原子云的自相似膨胀实验证明了这种纠缠可以在空间上分布。我们使用空间分辨的自旋读出来揭示一种特别强的量子相关性，称为爱因斯坦-波多尔斯基-罗森（Einstein-Podolsky-Rosen，EPR）导引，它存在于扩展云的不同部分之间。基于 EPR 导引的强度，我们构建了一个见证者，确认了真正的 5 部分纠缠。
