Bragg Scattering as a Probe of Atomic Wavefunctions and Quantum Phase Transitions in Optical Lattices

TL;DR

This paper demonstrates how Bragg scattering of photons can be used to probe atomic wavefunctions and detect quantum phase transitions, such as from superfluid to Mott insulator, in optical lattices.

Contribution

It introduces a novel method using Bragg scattering to directly measure microscopic atomic structures and coherence properties in quantum gases.

Findings

Bragg scattering reveals atomic wavefunction structure with Heisenberg-limited precision.

Revivals in scattered light indicate atomic Talbot effect and coherence.

Decay of revivals signals the superfluid to Mott insulator transition.

Abstract

We have observed Bragg scattering of photons from quantum degenerate $^{87}$Rb atoms in a three-dimensional optical lattice. Bragg scattered light directly probes the microscopic crystal structure and atomic wavefunction whose position and momentum width is Heisenberg-limited. The spatial coherence of the wavefunction leads to revivals in the Bragg scattered light due to the atomic Talbot effect. The decay of revivals across the superfluid to Mott insulator transition indicates the loss of superfluid coherence.