Quantum and Classical Dynamics of a BEC in a Large-Period Optical Lattice

TL;DR

This paper experimentally studies how a Bose-Einstein condensate diffracts in a large-period optical lattice, comparing quantum and classical models, revealing classical caustics shaping diffraction patterns.

Contribution

It provides the first detailed comparison of quantum and classical dynamics of BEC diffraction in large-period lattices, highlighting classical caustics effects.

Findings

Quantum and classical results show good agreement.

Classical caustics influence diffraction pattern envelopes.

Lattice period increase clarifies classical caustic effects.

Abstract

We experimentally investigate diffraction of a Rb-87 Bose-Einstein condensate from a 1D optical lattice. We use a range of lattice periods and timescales, including those beyond the Raman-Nath limit. We compare the results to quantum mechanical and classical simulations, with quantitative and qualitative agreement, respectively. The classical simulation predicts that the envelope of the time-evolving diffraction pattern is shaped by caustics: singularities in the phase space density of classical trajectories. This behavior becomes increasingly clear as the lattice period grows.