Theoretical Study of Silicon Based Quantum Information Processing

The overall objective of our research program is to help facilitate the realization of spin-based quantum computing in Si nanostructures. Our proposed research program consists of two main directions: coherent manipulation of a single spin qubit, and exchange coupling between spin qubits. Both are crucial in our long term goal of building a high fidelity large-scale Silicon- and spin-based quantum computer. On the front of single spin explorations, our major goals are to study spin coherence and control fidelity in the presence of static magnetic field gradient, and search for optimal conditions for spin control and coherence. On the front of multiple spin qubits, our major goal is to study the interplay between exchange coupling and valley mixing, and explore whether multielectron states in a dot/donor(s) can be used to encode a more robust spin qubit. On the front of noise and decoherence, we would like to study how interface defects could produce charge and magnetic noise. The goals set forth in this research program are all focused on helping identify optimal designs for high-fidelity single-qubit and two-qubit gates in a Silicon-spin-based quantum computer. Through this theoretical research program we have studied several important current issues in Silicon-based semiconductor quantum computing architectures, including the effects of an on-chip micromagnet, the effects of valley-orbit coupling in Si, and decoherence and control issues in spin qubit transport.