Finite resolution fluctuation measurements of a trapped Bose-Einstein condensate

摘要

We consider the fluctuations in atom number that occur within finite-sizedmeasurement cells in a trapped Bose-Einstein condensate (BEC). Thisapproximates the fluctuation measurements made in current experiments withfinite resolution in situ imaging. A numerical scheme is developed to calculatethese fluctuations using the quasiparticle modes of a cylindrically symmetricthree-dimensionally trapped condensate with either contact or dipole-dipoleinteractions (DDIs). We use this scheme to study the properties of a pancakeshaped condensate using cylindrical cells. The extension of the theory towasher shaped cells with azimuthal weighting is made and used to discriminatebetween the low energy roton modes in a dipolar condensate according to theirpro- jection of angular momentum. Our results are based on the Bogoliubovapproach valid for zero and small finite temperatures.