We observe dynamical fermionization, where the momentum distribution of a Tonks-Girardeau (T-G) gas of strongly interacting bosons in 1D evolves from bosonic to fermionic after its axial confinement is removed. The asymptotic momentum distribution after expansion in 1D is the distribution of rapidities, which are the conserved quantities associated with many-body integrable systems. Rapidities have not previously been measured in any interacting many-body quantum system. Our measurements agree well with T-G gas theory. We also study momentum evolution after the trap depth is suddenly changed to a new non-zero value. We observe the predicted bosonic-fermionic oscillations and see deviations from the theory outside of the T-G gas limit.1 arXiv:1908.05364v1 [cond-mat.quant-gas]
Monitoring quantum dynamics
Reducing the dimensionality of a quantum system of interacting particles can simplify its physics. Such reduction is possible in ultracold atomic gases, where a lattice of one-dimensional (1D) gases can be generated using optical potentials. Malvania
et al
. studied the dynamics of 1D rubidium-87 atomic gases after a sudden increase in the axial trapping potential. Normally, these dynamics would be difficult to describe theoretically, but the researchers found that a theory called generalized hydrodynamics captured the behavior of their 1D system over a long time evolution. —JS
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