Electron Spins in Quantum Dots as Qubits for Quantum Information Processing

Abstract

Coherent manipulation, filtering, and measurement of electronic spin in quantum dots and other nanostructures are new technologies which have promising applications both in conventional and in quantum information processing and transmission. We review the spintronics proposal for quantum computing, in which electron spins in quantum confined structures play the role of the quantum bits (qubits), and discuss the essential requirements for such an implementation. We describe several realizations of one- and twoqubit quantum gates and of state preparation and measurement, based on an all-electrical scheme to control the dynamics of spin. We discuss recently proposed schemes for using a single quantum dot as a spin filter and spin read-out device, and show how the decoherence time can be measured in a transport set-up. We address the issue of spin decoherence due to non-uniform hyperfine interactions with nuclei and show that for electrons confined to dots the spin decay is non-exponential. Finally, we discuss methods for producing and detecting the spin-entanglement of electronic EPR pairs, being an important resource for quantum communication.