Characterizing ultra-narrow momentum of atoms by standing-wave light-pulse sequences

We propose a method to characterize the ultra-narrow momentum distribution of atomic gases by employing a standing-wave light-pulse sequences beam splitter. The mechanism of beam splitting is analyzed in detail, and the influence of a finite-width momentum distribution on the population of each diffraction order is given. The temperature of ultracold atomic gases can be calibrated by measuring the ratio of population in different diffraction orders after double standing-wave light pulses. We obtain analytical expressions for two typical cases, and demonstrate phase space evolution in the whole process by using the Wigner function. This method is valid for both classical atomic gas and Bose–Einstein condensates, and it is suited for temperature measurement on the space ultracold atomic physics platform, in which the ultra-narrow momentum distribution of atomic gas is of the order of 100 pK or even lower.