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An All-Optical Quantum Gate in a Semiconductor Quantum Dot

Xiaoqin Li, Yanwen Wu, Duncan G. Steel, D. Gammon, Todd H. Stievater, Douglas Scott Katzer, Daeui Park, Carlo Piermarocchi, Lu Jeu Sham

Published Aug 8, 2003• 899 citations

Abstract

We report coherent optical control of a biexciton (two electron-hole pairs), confined in a single quantum dot, that shows coherent oscillations similar to the excited-state Rabi flopping in an isolated atom. The pulse control of the biexciton dynamics, combined with previously demonstrated control of the single-exciton Rabi rotation, serves as the physical basis for a two-bit conditional quantum logic gate. The truth table of the gate shows the features of an all-optical quantum gate with interacting yet distinguishable excitons as qubits. Evaluation of the fidelity yields a value of 0.7 for the gate operation. Such experimental capability is essential to a scheme for scalable quantum computation by means of the optical control of spin qubits in dots.

DOI: 10.1126/science.1083800

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