| The controlled, coherent manipulation of quantum-mechanical systems is an important challenge in modern science and engineering, with significant applications in quantum information science. Solid-state quantum systems such as electronic spins, nuclear spins, and superconducting islands are among the most promising candidates for realization of quantum bits (qubits). However, in contrast to isolated atomic systems, these solid-state qubits couple to a complex environment which often results in rapid loss of coherence, and, in general, is difficult to understand. Additionally, the strong interactions which make solid-state quantum systems attractive can typically only occur between neighboring systems, leading to difficulties in coupling arbitrary pairs of quantum bits.; This thesis presents experimental progress in understanding and controlling the complex environment of a solid-state quantum bit, and theoretical techniques for extending the distance over which certain quantum bits can interact coherently. Coherent manipulation of an individual electron spin associated with a nitrogen-vacancy center in diamond is used to gain insight into its mesoscopic environment. Furthermore, techniques for exploiting coherent interactions between the electron spin and a subset of the environment are developed and demonstrated, leading to controlled interactions with single isolated nuclear spins. The quantum register thus formed by a coupled electron and nuclear spin provides the basis for a theoretical proposal for fault-tolerant long-distance quantum communication with minimal physical resource requirements. Finally, we consider a mechanism for long-distance coupling between quantum dots based on chip-scale cavity quantum electrodynamics. |
