Optical Spin Initialization and Non-Destructive Measurement in a Quantum Dot Molecule

TL;DR

This paper demonstrates optical methods for initializing and non-destructively measuring electron spins in a quantum dot molecule using resonant laser spectroscopy, achieving simultaneous operations in a single quantum dot.

Contribution

It introduces a novel technique combining spin initialization and non-destructive measurement in a quantum dot molecule with two-laser spectroscopy.

Findings

Successful optical spin initialization via spin-flip Raman transitions.

Non-destructive measurement enabled by cycling transitions.

Simultaneous operation of both processes in a single quantum dot.

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 non-destructive measurement. With two-laser transmission spectroscopy we demonstrate both operations simultaneously, something not previously accomplished in a single quantum dot.