Comments on "Asking Photons Where They Have Been"
  By using the nonuniform discrete Fourier transform on the center positions of the symmetric intensity distribution of the output beam, we recover the vibration information of two mirrors, which is lost in the analysis of Danan \emph{et al.} in the work [Phys. Rev. Lett. \textbf{111}, 240402 (2013), arXiv:1304.7469]. We believe a photon always follows continuous trajectories, and a photon has to enter an interferometer at first and then leave it, if this photon has ever been inside the interferometer. 
Jie-Hui Huang, Li-Yun Hu, Xue-Xiang Xu, Cun-Jin Liu, Qin Guo,   Hao-Liang Zhang, and Shi-Yao Zhu
quant-ph