Decoherence in quantum dots due to real and virtual transitions: A nonperturbative calculation

We investigate theoretically acoustic phonon-induced decoherence in quantum dots. We calculate the dephasing of fundamental (interband or intraband) optical transitions due to real and virtual transitions with higher energy levels. Up to two acoustic phonon processes (absorption and/or emission) are taken into account simultaneously in a nonperturbative manner. An analytic expression of acoustic phonon-induced broadening is given as a function of the electron-phonon matrix elements and is physically interpreted. The theory is applied to the dephasing of intersublevel transitions in self-assembled quantum dots.