It is well accepted that atomic non-sequential double ionization (NSDI) process in intense infrared laser field can be well understood from a semiclassical perspective. Observation of quantum interference effect in NSDI is obscured by low statistic of coincidence measurement in COLTRIMS experiment, focal average effect and complication of the process, therefore, still remains a challenge in both experimental and theoretical study of strong-field atomic physics. Recent progress in experimental technique and theoretical method makes it possible to measure the process more accurately and reveal new effect related to quantum interference effect in the NSDI process. In this talk, I will discuss some recent efforts in our understanding of this intriguing phenomenon including experimental measurement of electron momentum distribution in wide range of laser parameters, i. e., intensity, pulse duration and wavelength, and theoretical investigation to comprehend the experimental result with quantum approaches incorporating excited state effect and quantitative description of the Coulomb interaction between the ions and photoelectrons.
References  Y. Liu, et.al., Phys. Rev. Lett. 101, 053001 (2008).  X. Hao, et.al., Phys. Rev. Lett. 112, 073001 (2014).  M. Kübel et al., New J. Phys. 16, 033008 (2014).  A. S. Maxwell and C. Figueira de Morisson Faria, Phys. Rev. Lett. 116, 143001 (2017).  W. Quan, et al., Phys. Rev. A 96, 032511 (2017).  W. Quan, et al., Phys. Rev. Lett. 119, 243203 (2017).