Measurement of phase fluctuations of Bose-Einstein condensates in an optical lattice

TL;DR

This paper presents a method to measure phase fluctuations in Bose-Einstein condensates within an optical lattice by analyzing the Fourier spectrum of atomic density, effective even at high lattice strengths where interference peaks vanish.

Contribution

It introduces a novel Fourier spectrum-based technique to quantify phase fluctuations in Bose-Einstein condensates in optical lattices, including in regimes with strong lattice confinement.

Findings

The method accurately measures phase variance from Fourier spectra.

It remains effective even when interference peaks are absent.

The approach provides insights into phase coherence at zero temperature.

Abstract

Even at zero temperature, there exist phase fluctuations associated with an array of Bose-Einstein condensates confined in a one-dimensional optical lattice. We demonstrate a method to measure the phase fluctuations based on the Fourier spectrum of the atomic density for a condensate released from the optical lattice. The phase variance is extracted from the relative intensities of different peaks in the Fourier spectrum. This method works even for high lattice strength where interference peaks disappear in the atomic density distribution.