Optimal Control of Quantum Rings by Terahertz Laser Pulses

Physical Review Letters 98, 157404 - 4 (2007)

Optimal Control of Quantum Rings by Terahertz Laser Pulses

E. Räsänen, A. Castro, J. Werschnik, A. Rubio

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.

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