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SYQI: Quantum information processing in condensed media

SYQI 1: Quantum information processing in condensed media I

SYQI 1.3: Vortrag

Montag, 24. März 2003, 14:15–14:30, HSZ/01

Optimal Control of One-Qubit Gates — •Karen M. Fonseca Romero^1,2 and Gina Useche Laverde² — ¹Institut für Physik, Universität Augsburg — ²Departamento de Física, Universidad Nacional de Colombia

The boundary problem for the time evolution of a Bloch vector is formulated within the classical theory of optimal control. The possibility to steer an initial Bloch vector to a target in a specified amount of time under the action of three control fields is demonstrated. The physically motivated criteria of minimum energy spent in the control, minimum magnitude of the rate of change of the control and a combination of both, allow an exact analytical treatment. The control fields are explicitly given for a general one qubit gate. The case of a single control for minimum energy is also solved exactly for a Y gate. The effect of small decoherence on the target fidelity is addressed numerically and shown to be state dependent. Optimization in the presence of decoherence is discussed