Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL University, Sorbonne Université, 75005 Paris, France.
Science. 2021 Sep 17;373(6561):1340-1343. doi: 10.1126/science.abd8206. Epub 2021 Sep 16.
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.
弱相互作用玻色气体通常形成玻色-爱因斯坦凝聚态，其中大多数粒子占据相同的单粒子态。然而，当这个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的分裂凝聚态。在这里，我们为大约 100 个原子的介观自旋-1 气体产生了一个三碎片凝聚态，具有反铁磁相互作用和零集体自旋。通过接近单原子分辨率的自旋分辨探测，我们表明重构态接近于预期的多体基态，而单粒子可观测量与完全混合态相同。我们的结果强调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。
