Hulet, Randall G2024-01-242024-01-242024-052023-12-04May 2024Espinoza Masbernat, Ricardo. "Overcoming Decoherence to Observe Quantum Fluctuations in Matter-Wave Breathers." (2023). Master's thesis, Rice University. https://hdl.handle.net/1911/115384https://hdl.handle.net/1911/115384The 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.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.BreathersQuantum FluctuationsBose-Einstein CondensateThesis2024-01-24