Stimulated and spontaneous optical generation of electron spin coherence in charged GaAs quantum dots

TL;DR

This paper demonstrates the coherent optical control of electron spin states in charged GaAs quantum dots, revealing a spin decoherence time near 10 ns and uncovering the role of spontaneous decay in spin coherence.

Contribution

It introduces a method for optical excitation and detection of spin coherence in quantum dots, highlighting the influence of spontaneous decay on Raman spin coherence.

Findings

Spin decoherence time approaches 10 ns at zero magnetic field.

Raman spin coherence is driven by stimulated Raman interaction and spontaneous radiative decay.

Spontaneous decay contributes to the quantum beats in spin coherence.

Abstract

We report on the coherent optical excitation of electron spin polarization in the ground state of charged GaAs quantum dots via an intermediate charged exciton (trion) state. Coherent optical fields are used for the creation and detection of the Raman spin coherence between the spin ground states of the charged quantum dot. The measured spin decoherence time, which is likely limited by the nature of the spin ensemble, approaches 10 ns at zero field. We also show that the Raman spin coherence in the quantum beats is caused not only by the usual stimulated Raman interaction but also by simultaneous spontaneous radiative decay of either excited trion state to a coherent combination of the two spin states.