Coupling and state transfer in Josephson qubit systems

Abstract

The quantum information science (QIS) is relatively young, but quite broad and emerging field of modern physics. This is an interdisciplinary field where quantum mechanics, computer science, mathematics and computing technologies meet together. Using the laws of quantum mechanics to deal with information opens many new opportunities. However, these opportunities can only be used if one can construct a quantum logic device to implement QIS methods. In the last decade many researchers proposed the variety of physical systems, that can be used as building blocks of the so called quantum computer. But the question of building an effective connection between different blocks remains open. Recently, the idea to build a ’quantum wire’ using chains of permanently coupled spins was studied by a number of authors. The purpose of this thesis is to investigate and develop advanced schemes for using quantum chains as wires. The first part of the thesis shortly describes the concepts of quantum computing and quantum state transfer. We then briefly introduce different schemes to couple two superconducting qubits and analyze more closely one of them. Then we analyze the process of the state transfer for the chain of flux qubits. Next, we propose a new method of improved quantum state transfer which was created as a part of this thesis. Finally, we study the effects and the role of interference in quantum state transfer via spin chains.