Optical quantum gates with semiconductor nanostructures

An all optical implementation of quantum information processing with semiconductor macroatoms is presented. Our quantum hardware consists of an array of semiconductor quantum dots and the computational degrees of freedom, i.e. the qubits, are energy-selected interband optical transitions. The proposed quantum-computing scheme exploits exciton–exciton interactions driven by ultrafast sequences of multicolour laser pulses. Contrary to existing proposals based on charge excitations, the present all-optical implementation does not require the application of time-dependent electric !elds, thus allowing for a sub-picosecond, i.e. decoherence-free, operation time-scale in realistic state-of-the-art semiconductor nanostructures. Moreover, the fully-optical character of the proposed gating scheme makes it an ideal candidate for the realization of all-optical computing networks.