An All-Optical Quantum Gate in a Semiconductor Quantum Dot

TLDR

Experimental control of spin qubits in quantum dots is essential for scalable optical quantum computation. Pulse control of biexciton dynamics combined with single‑exciton Rabi rotation underpins a two‑bit conditional quantum logic gate. Coherent optical control of a biexciton in a single quantum dot yields a two‑bit conditional quantum gate with a truth table matching expected behavior and a fidelity of 0.7.

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.