Gaussian trajectory description of fragmentation in an isolated spinor condensate

Spin-1 Bose gases quenched to spin degeneracy exhibit fragmentation: the appearance of a condensate in more than one single-particle state. Due to its highly entangled nature, the dynamics leading to this collective state are beyond the scope of a Gaussian variational approximation of the many-body wave function. Here, we improve the performance of the Gaussian variational ansatz by considering dissipation into a fictitious environment, effectively suppressing entanglement within individual quantum trajectories at the expense of introducing a classical mixture of states. We find that this quantum trajectory approach captures the dynamical formation of a fragmented condensate and analyze how much dissipation should be added to the experiment in order to keep a single realization in a nonfragmented state.

Automated summary

Spin-1 Bose gases quenched to spin degeneracy exhibit fragmentation, with a condensate appearing in multiple single-particle states. By considering dissipation, we improve the performance of the Gaussian variational ansatz and effectively suppress entanglement, capturing the formation of a fragmented condensate. We analyze the amount of dissipation required to maintain a nonfragmented state.