Weakly interacting Bose gases usually form Bose-Einstein condensates in which most particles occupy the same single-particle state. However, when this state cannot realize a continuous symmetry of the many-body Hamiltonian, a fragmented condensate exhibiting the expected symmetry may emerge. Here, we produced a three-fragment condensate for a mesoscopic spin-1 gas of about 100 atoms, with anti-ferromagnetic interactions and vanishing collective spin. Using a spin-resolved detection approaching single-atom resolution, we show that the reconstructed state is close to the expected many-body ground state, whereas one-body observables are the same as for a completely mixed state. Our results highlight how the interplay between symmetry and interactions generates entanglement in a mesoscopic quantum system.

中文翻译：

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旋量玻色-爱因斯坦凝聚体碎裂的观察

弱相互作用的玻色气体通常形成玻色-爱因斯坦凝聚体，其中大多数粒子处于相同的单粒子状态。然而，当这种状态不能实现多体哈密顿量的连续对称时，可能会出现表现出预期对称性的碎片凝聚物。在这里，我们为大约 100 个原子的介观自旋 1 气体产生了三片段凝聚物，具有反铁磁相互作用和消失的集体自旋。使用接近单原子分辨率的自旋分辨检测，我们表明重建状态接近预期的多体基态，而单体可观测与完全混合状态相同。我们的结果突出了对称性和相互作用之间的相互作用如何在介观量子系统中产生纠缠。