(color online) (a) Energy diagram of TPE. (b) Photofluorescence spectra of the same QD, under non-resonant excitation (upper) and TPE (lower).^[99] (c) Scheme of a pulse shaper to generate the chirp pulse (upper), and generation of a biexciton with broadband, chirped excitation (lower).^[100] (d) Photofluorescence spectrum of a GaAs QD under phonon-assisted TPE for optimized detuning of the laser energy, pulse length ( ) and a pulse area of 6π. (e) Population of the exciton state as a function of the laser detuning for varying the excitation power.^[101]