title: Optimal control of quantum rings by terahertz laser pulses.
abstract: Complete control of single-electron states in a two-dimensional semiconductor quantum-ring model is established, opening a path into coherent laser-driven single-gate qubits. The control scheme is developed in the framework of optimal-control theory for laser pulses of two-component polarization. In terms of pulse lengths and target-state occupations, the scheme is shown to be superior to conventional control methods that exploit Rabi oscillations generated by uniform circularly polarized pulses. Current-carrying states in a quantum ring can be used to manipulate a two-level subsystem at the ring center. Combining our results, we propose a realistic approach to construct a laser-driven single-gate qubit that has switching times in the terahertz regime.
authors.affiliation: Institut für Theoretische Physik, Freie Universität Berlin, Berlin, Germany. esa@physik.fu-berlin.de
authors.forename: E
authors.initials: E
authors.lastname: Räsänen
authors.forename: A
authors.initials: A
authors.lastname: Castro
authors.forename: J
authors.initials: J
authors.lastname: Werschnik
authors.forename: A
authors.initials: A
authors.lastname: Rubio
authors.forename: E K U
authors.initials: EK
authors.lastname: Gross