The binding energy and wavefunctions of the is, 1 p, 1d and if energy states of a spherical quantum dot (QD) with parabolic potential were calculated by using a method which is a combination of the quantum genetic algorithm (QGA) and the Hartree-Fock-Roothaan (HFR) approach. In addition, the linear and the third-order nonlinear optical absorption coefficients based on optical transitions in QDs with and without impurity were calculated. The results show that the parabolic potential has a great effect not only on the binding energies and but also on the optical absorption coefficients. Moreover, the calculated results also reveal that the linear and nonlinear optical absorption coefficients are strongly affected by the existence of impurity and the incident optical intensity. (C) 2009 Elsevier Ltd. All rights reserved.