  We construct an optimal set of single-particle states for few-electron
quantum dots (QDs) using the method of natural orbitals (NOs). The NOs include
also the effects of the Coulomb repulsion between electrons. We find that they
agree well with the noniteracting orbitals for GaAs QDs of realistic
parameters, while the Coulomb interactions only rescale the radius of the NOs
compared to the noninteracting case. We use NOs to show that four-electron QDs
are less susceptible to charge noise than their two-electron counterparts.
