Coherent driving of direct and indirect excitons in a quantum dot molecule

TL;DR

This paper demonstrates coherent control of exciton states in quantum dot molecules, enabling optimized quantum light sources for graph state generation through voltage-tuned exciton manipulation.

Contribution

It introduces a method to coherently drive and transition between direct and indirect excitons in quantum dot molecules, enhancing quantum photonic applications.

Findings

Power-dependent Rabi oscillations observed in exciton states

Voltage control enables transition between exciton types

Optimized conditions for quantum graph state generation

Abstract

Quantum dot molecules (QDMs) are one of the few quantum light sources that promise deterministic generation of one- and two-dimensional photonic graph states. The proposed protocols rely on coherent excitation of the tunnel-coupled and spatially indirect exciton states. Here, we demonstrate power-dependent Rabi oscillations of direct excitons, spatially indirect excitons, and excitons with a hybridized electron wave function. An off-resonant detection technique based on phonon-mediated state transfer allows for spectrally filtered detection under resonant excitation. Applying a gate voltage to the QDM-device enables a continuous transition between direct and indirect excitons and, thereby, control of the overlap of the electron and hole wave function. This does not only vary the Rabi frequency of the investigated transition by a factor of $\approx3$, but also allows to optimize graph state generation in terms of optical pulse power and reduction of radiative lifetimes.