Quantum Computing in Solid State, and Coherent Behavior of Open Quantum Systems

摘要

We have developed and investigated models of realization of quantum computing in solid-state semiconductor heterostructures, and explored decoherence properties of relevance in evaluation of quantum-computing systems. Quantum bits (qubits) are nuclear or outer bound electron spins in donor atoms embedded in the zero-spin host material, which could be an isotope of Si. In order to accomplish control of each qubit and also have controlled qubit-qubit interactions, we consider exchange of electrons, either bound or in two- dimensional electron gas. Our emphasis has been on spin-excitons that form in the electron gas in heterostructures under quantum Hall effect conditions: at low temperatures and in high magnetic fields. Their spectral gap causes slow relaxation and decoherence, while still allowing controlled qubit-qubit interactions at qubit separations of order 100 nm. We have carried detailed many-body perturbative calculations of qubit interactions and decoherence in such systems. We have also obtained results promoting general understanding of quantum decoherence and measurement processes, within the setting appropriate for quantum computing applications.