Capturing the transformation Quantum statistics dictates the behavior of identical particles in the quantum world: Bosons like to congregate, whereas fermions avoid one another. However, strong interactions can cause a string of bosons to behave like fermions. This so-called fermionization phenomenon has been studied in equilibrium. Wilson et al. instead focused on dynamical fermionization in a nonequilibrium system consisting of tubes of strongly interacting bosonic rubidium atoms. After letting the tubes expand in the axial direction, the researchers monitored the momentum distribution of the atoms and found that it evolved from bosonic-like to fermionic-like. Science, this issue p. 1461 The momentum distribution of an expanding one-dimensional Bose gas evolves from bosonic to fermionic. The wave function of a Tonks-Girardeau (T-G) gas of strongly interacting bosons in one dimension maps onto the absolute value of the wave function of a noninteracting Fermi gas. Although this fermionization makes many aspects of the two gases identical, their equilibrium momentum distributions are quite different. We observed dynamical fermionization, where the momentum distribution of a T-G gas evolves from bosonic to fermionic after its axial confinement is removed. The asymptotic momentum distribution after expansion in one dimension is the distribution of rapidities, which are the conserved quantities associated with many-body integrable systems. Our measurements agree well with T-G gas theory. We also studied momentum evolution after the trap depth is suddenly changed to a new nonzero value, and we observed the theoretically predicted bosonic-fermionic oscillations.

中文翻译：

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观察动态费米化

捕捉转换 量子统计决定了量子世界中相同粒子的行为：玻色子喜欢聚集，而费米子相互避开。然而，强相互作用会导致一串玻色子表现得像费米子。这种所谓的费米化现象已经在平衡状态下进行了研究。威尔逊等人。而是专注于非平衡系统中的动态费米化，该系统由强相互作用的玻色铷原子管组成。在让管子沿轴向膨胀后，研究人员监测了原子的动量分布，发现它从类玻色子演化为类费米子。科学，这个问题 p。1461 膨胀的一维玻色气体的动量分布从玻色子演变为费米子。一维强相互作用玻色子的汤克斯-吉拉多 (TG) 气体的波函数映射到非相互作用费米气体的波函数的绝对值。尽管这种费米化使两种气体的许多方面相同，但它们的平衡动量分布却大不相同。我们观察到动态费米化，即在去除轴向限制后，TG 气体的动量分布从玻色子演变为费米子。一维展开后的渐近动量分布是速度的分布，是与多体可积系统相关的守恒量。我们的测量结果与 TG 气体理论非常吻合。我们还研究了陷阱深度突然变为新的非零值后的动量演化，