The Excitonic Quantum Computer

A review of semiconductor-based schemes for the realization of quantum information processing devices is presented. After recalling the fundamentals of quantum information/computation theory, we shall discuss potential implementation schemes based on charge and/or spin degrees of freedom in semiconductor nanostructures. More specifically, we shall present an all-optical implementation scheme of quantum information processing with semiconductor macroatoms/molecules, where the computational degrees of freedom are interband optical transitions (excitonic states) manipulated/controlled by ultrafast sequences of multicolor laser pulses. We shall primarily focus on implementation schemes dealing with charge excitations in GaAs as well as GaN quasi-zero-dimensional structures. We shall finally discuss the possibility to combine charge and spin degrees of freedom, thus allowing for fast quantum gates which do not translate into fast decoherence times.