Spintronics, quantum computing, and quantum communication in quantum dots

The coherent manipulation, filtering, and measurement of the electron spin in solid-state nanostructures has potential applications for both conventional and quantum computation as well as for quantum communication. This article is intended as a review of our proposal to use electron spins in quantum confined structures as quantum bits (qubits). The physical requirements for implementing a quantum computer, including single- and two-qubit gate operations, phase coherence, initialization, and read-out, will be discussed. In addition, we also present recently proposed schemes for using a single quantum dot as spin-filter and spin-memory device. In the context of spintronics, it is quite natural to consider spin-entangled electron pairs as a basic resource for quantum communication; we show that the entanglement of such EPR pairs can be detected in mesoscopic transport measurements using metallic as well as superconducting leads attached to the dots.