Characterization and control of quantum spin chains and rings

Information flow in quantum spin networks is considered. Two types of control - temporal bang-bang switching control and control by varying spatial degrees of freedom - are explored and shown to be effective in speeding up information transfer and increasing transfer fidelities. The control is modelbased and therefore relies on accurate knowledge of the system parameters. An efficient protocol for simultaneous identification of the coupling strength and the exact number of spins in a chain is presented.