Honda Kantaro, Takasu Yosuke, Goto Shimpei, Kazuta Hironori, Kunimi Masaya, Danshita Ippei, Takahashi Yoshiro
Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
Institute for Liberal Arts, Institute of Science Tokyo, Ichikawa, Chiba 272-0827, Japan.
Sci Adv. 2025 Jun 6;11(23):eadv3255. doi: 10.1126/sciadv.adv3255.
While isolated quantum systems generally thermalize after long-time evolution, there are several exceptions defying thermalization. A notable mechanism of this nonergodicity is the Hilbert space fragmentation (HSF), where the Hamiltonian matrix splits into an exponentially large number of sectors due to the presence of nontrivial conserved quantities. Using ultracold gases, here, we experimentally investigate the one-dimensional Bose-Hubbard system with neither disorder nor tilt potential, which has been predicted to exhibit HSF caused by a strong interatomic interaction. Specifically, we analyze far-from-equilibrium dynamics starting from a charge density wave of doublons (atoms in doubly occupied sites) in a singlon- and doublon-resolved manner to reveal a slowing down of the relaxation in a strongly interacting regime. We find that the numbers of singlons and doublons are conserved during the dynamics, indicating HSF as a mechanism of the observed slow relaxation. Our results provide an experimental confirmation of the conserved quantities responsible for HSF.
虽然孤立的量子系统在长时间演化后通常会热化，但存在一些违背热化的例外情况。这种非遍历性的一个显著机制是希尔伯特空间碎片化（HSF），由于存在非平凡的守恒量，哈密顿矩阵会分裂成指数级大量的扇区。在此，我们使用超冷气体对既无无序也无倾斜势的一维玻色 - 哈伯德系统进行实验研究，该系统已被预测会因强原子间相互作用而表现出HSF。具体而言，我们以单占据子和双占据子分辨的方式，从双占据子（双占据位点上的原子）的电荷密度波开始分析远离平衡的动力学，以揭示强相互作用区域中弛豫的减慢。我们发现，在动力学过程中单占据子和双占据子的数量是守恒的，这表明HSF是观察到的缓慢弛豫的一种机制。我们的结果为导致HSF的守恒量提供了实验证实。
