Optical spin initialization and nondestructive measurement in a quantum dot molecule

Phys Rev Lett. 2008 Dec 5;101(23):236804. doi: 10.1103/PhysRevLett.101.236804. Epub 2008 Dec 2.

Abstract

The spin of an electron in a self-assembled InAs/GaAs quantum dot molecule is optically prepared and measured through the trion triplet states. A longitudinal magnetic field is used to tune two of the trion states into resonance, forming a superposition state through asymmetric spin exchange. As a result, spin-flip Raman transitions can be used for optical spin initialization, while separate trion states enable cycling transitions for nondestructive measurement. With two-laser transmission spectroscopy we demonstrate both operations simultaneously, something not previously accomplished in a single quantum dot.