The description of quantum many-body phenomena that go beyond a mean-field approximation is often difficult or, more typically, impossible to achieve. Experiments in this regime are also challenging due to technological constraints. An exception may be the dissociation of matter-wave breathers, which in 1D are exactly integrable solutions of the mean-field Gross-Pitaevskii equation, by quantum fluctuations. Breathers are coherent superpositions of fundamental solitons.

To study these effects on the decoherence of 7Li matter-wave breathers, we first characterize the decoherence due to mean-field phenomena in quasi-1D. We find that mean-field decoherence of breathers is caused primarily by density-dependent atom loss.

We also find that the mechanisms of atom loss present in our experiment, i.e. inelastic collisions with background gas and three-body recombination, have different effects on breather coherence.

After identifying the sources of mean-field decoherence, we seek to suppress them so that dissociation by quantum fluctuations may be observable. For this purpose, we present a theoretical proposal and its experimental implementation aimed at enhancing the measure of breather dissociation, i.e. the relative distance between constituent solitons, via expansion in an anti-trapping harmonic potential.