Ultrafast Quantum Information Processing in Nanostructured Semiconductors

We shall review two implementation proposals for quantum information processing based on charge degrees of freedom in semiconductor nanostructures. An all-optical implementation scheme using semiconductor macroatoms/molecules will be discussed. The computational degrees of freedom in this proposal are interband optical transitions driven by ultrafast sequences of multicolor laser-pulse trains. The conditional dynamics necessary for universal quantum computation is provided by exciton–exciton coupling between different quantum dots in an array. We shall also discuss an alternative scheme based on transport of ballistic electrons in coupled semiconductor quantum wires. In the framework of such implementation strategy, we shall finally discuss a potential simple way for testing violation of Bell’s inequality in a condensed-matter setting.