Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany.
Nature. 2010 May 13;465(7295):197-201. doi: 10.1038/nature09036.
Interactions lie at the heart of correlated many-body quantum phases. Typically, the interactions between microscopic particles are described as two-body interactions. However, it has been shown that higher-order multi-body interactions could give rise to novel quantum phases with intriguing properties. So far, multi-body interactions have been observed as inelastic loss resonances in three- and four-body recombinations of atom-atom and atom-molecule collisions. Here we demonstrate the presence of effective multi-body interactions in a system of ultracold bosonic atoms in a three-dimensional optical lattice, emerging through virtual transitions of particles from the lowest energy band to higher energy bands. We observe such interactions up to the six-body case in time-resolved traces of quantum phase revivals, using an atom interferometric technique that allows us to precisely measure the absolute energies of atom number states at a lattice site. In addition, we show that the spectral content of these time traces can reveal the atom number statistics at a lattice site, similar to foundational experiments in cavity quantum electrodynamics that yield the statistics of a cavity photon field. Our precision measurement of multi-body interaction energies provides crucial input for the comparison of optical-lattice quantum simulators with many-body quantum theory.
相互作用处于关联多体量子相的核心。通常，微观粒子之间的相互作用被描述为二体相互作用。然而，已经表明，更高阶的多体相互作用可以产生具有有趣性质的新型量子相。到目前为止，多体相互作用已经在原子-原子和原子-分子碰撞的三体和四体复合的非弹性损耗共振中被观察到。在这里，我们在三维光晶格中展示了超冷玻色原子系统中存在有效的多体相互作用，这些相互作用是通过粒子从最低能带向更高能带的虚拟跃迁而产生的。我们使用原子干涉技术在量子相位恢复的时间分辨轨迹中观察到了这种相互作用，直到六体情况，该技术允许我们精确测量晶格位置处原子数态的绝对能量。此外，我们还表明，这些时间轨迹的光谱内容可以揭示晶格位置处的原子数统计，类似于腔量子电动力学中的基础实验，这些实验可以得到腔光子场的统计。我们对多体相互作用能量的精确测量为光晶格量子模拟器与多体量子理论的比较提供了关键输入。
