Few-particle states and quantum-information processing in quantum dots

Summary form only given. The strong three-dimensional quantum confinement in semiconductor quantum dots (QDs) results in a discrete, atomic-like carrier density of states. In turn, the coupling to the solid-state environment (e.g. phonons) is strongly suppressed and Coulomb correlations among charge carriers are strongly enhanced. Indeed, in the optical spectra of single dots spectrally narrow emission peaks have been observed (indicating a small environment coupling), which undergo discrete energy shifts when more carriers are added to the dot (indicating energy renormalizations due to additional Coulomb interactions). In this paper, we discuss how these spectral changes result from few-particle interactions. In our calculations, we use prototypical dot confinements and obtain the Coulomb-renormalized few-particle states through direct diagonalization of the Hamiltonian matrix. We also demonstrate that exciton states in quantum dots can serve as qubits, where the requested quantum gates can be implemented by use of ultrafast spectroscopy and coherent-carrier control.