Time-resolved density correlations as a probe of squeezing in toroidal Bose–Einstein condensates

Abstract

The author studies the evolution of mean-field and linear quantum fluctuations in a toroidal Bose–Einstein condensate, whose interaction strength is quenched from a finite (repulsive) value to zero. The azimuthal equal-time density–density correlation function is calculated and shows temporal oscillations with twice the (final) excitation frequencies after the transition. These oscillations are a direct consequence of positive and negative frequency mixing during non-adiabatic evolution. The author argues that a time-resolved measurement of the equal-time density correlator might be used to calculate the moduli of the Bogoliubov coefficients and thus the amount of squeezing imposed on a mode, i.e. the number of atoms excited out of the condensate.