Quantum switching at a mean-field instability of a Bose-Einstein condensate in an optical lattice

TL;DR

This paper investigates how bifurcations in the mean-field dynamics of a Bose-Einstein condensate in an optical lattice relate to quantum phase transitions, demonstrating controllable switching behavior and macroscopic effects of microscopic differences.

Contribution

It establishes a connection between mean-field bifurcations and quantum phase transitions in Bose-Einstein condensates, with experimental implications for control and visualization.

Findings

Switching between self-trapping states observed.

Transition from self-trapping to superposition near bifurcation.

Microscopic atom number differences lead to macroscopic dynamics.

Abstract

It is shown that bifurcations of the mean-field dynamics of a Bose-Einstein condensate can be related with the quantum phase transitions of the original many-body system. As an example we explore the intra-band tunneling in the two-dimensional optical lattice. Such a system allows for easy control by the lattice depth as well as for macroscopic visualization of the phase transition. The system manifests switching between two selftrapping states or from a selftrapping state to a superposition of the macroscopically populated selftrapping states with the step-like variation of the control parameter about the bifurcation point. We have also observed the magnification of the microscopic difference between the even and odd number of atoms to a macroscopically distinguishable dynamics of the system.