Interference of a chain of Bose condensates in the Pitaevskii-Gross approximation

TL;DR

This paper models the interference patterns of a chain of Bose condensates after expansion, analyzing phase fluctuations and coherence effects, and compares theoretical predictions with experimental data.

Contribution

It provides a theoretical analysis of condensate interference using the Pitaevskii-Gross equation, highlighting the spectral features and their relation to phase coherence.

Findings

Interference fringes are well-resolved regardless of phase fluctuations.

The spectrum of density distribution is reproducible despite phase fluctuations.

Theoretical peak positions match experimental observations, but peak heights sometimes differ.

Abstract

A long chain of Bose condensates freely expands and interferes after being released from an optical lattice. The interference fringes are well resolved both in the case of equal phases of the condensates and in the case of fluctuating phases. In the second case the positions of the fringes also fluctuate. The spectrum of the spatial density distribution, however, is reproducible despite the fluctuations. Moreover two types of peaks are distinguishable in the spectrum. The first type arises due to the phase fluctuations, the second type is associated with the coherence between the condensates. In the framework of the Pitaevskii-Gross equation we calculate the interference of the condensates and compare the calculation with experiment [Phys. Rev. Lett. 122, 090403 (2019)]. The calculation reproduces the positions of the spectrum peaks, including the dependence on the interparticle interaction. The calculated heights of the peaks, however, in some cases differ with the experimental ones.