Analysis Of The XY Spin 1/2 Model In Staggered Field And Networks Of D-Wave Josephson Junctions

by Crooks, Richard Henry, PhD

The study of entanglement in quantum systems is an area of much recent experimental and theoretical work and is of central importance in the implementation of various protocols in quantum information science. The dynamical properties of entanglement are examined in the context of the XY spin 1/2 chain model with a staggered magnetic field. The quality of entangled state transfer is found to be comparable to the uniform field XY spin 1/2 chain in the strong field regime. The effects of anisotropy on state transfer is also considered, as well as the interaction between entanglement waves and the possibility of transmission of multiple bits of quantum information. As an additional system where these quantum entanglement dynamics might play out, a large array of mesoscopic junctions made out of gapless unconventional superconductors is also studied. In this model, the tunneling processes of both particle-hole and Cooper pairs give rise to a strongly retarded effective action which, contrary to the case of conventional superconductors, cannot be readily characterized in terms of a local Josephson energy. This is an action that describes, for example, grain boundary and c-axis junctions in layered high-Tc superconductors. The emergent collective phenomena in this system are obtained, along with the phase diagram and the electrical conductivity of the model.