Second Order Correlation Function of a Phase Fluctuating Bose-Einstein Condensate

TL;DR

This paper investigates the phase coherence properties of elongated Bose-Einstein condensates through theoretical derivation and experimental measurement of the second order correlation function, providing insights into their coherence length.

Contribution

It presents a new theoretical expression for N-particle correlations and demonstrates an interferometric method to measure the second order correlation function experimentally.

Findings

Measured the second order correlation function of a highly elongated condensate.

Demonstrated the phase coherence length using a Bragg diffraction interferometer.

Provided a method to characterize phase fluctuations in Bose-Einstein condensates.

Abstract

The coherence properties of phase fluctuating Bose-Einstein condensates are studied both theoretically and experimentally. We derive a general expression for the N-particle correlation function of a condensed Bose gas in a highly elongated trapping potential. The second order correlation function is analyzed in detail and an interferometric method to directly measure it is discussed and experimentally implemented. Using a Bragg diffraction interferometer, we measure intensity correlations in the interference pattern generated by two spatially displaced copies of a parent condensate. Our experiment demonstrates how to characterize the second order correlation function of a highly elongated condensate and to measure its phase coherence length.