Erratum: 'Evidence of photon acceleration by laser wake fields' [Phys. Plasmas 13, 033108 (2006)]

Original article: Physics of Plasmas 13, 033108 (2006) References to the technique employed to determine the numerical Wigner transform were missing, which are presented here for the sake of completeness. The numerical Wigner transform presented in Fig. 4 was calculated using the MATLAB HOSA Toolbox,1 employing the analytic signal. The different numerical approaches to evaluate the Wigner transform are discussed in detail by Bizarro et al.2 Some of the authors (F. F. and L. O. S.) acknowledge discussions with A. Figueiredo and J. P. S. Bizarro regarding some of the properties of the discrete Wigner transform.