Dissipative preparation of the exciton and biexciton in a self-assembled quantum dot on picosecond timescales

TL;DR

This paper demonstrates ultrafast, high-fidelity preparation of exciton and biexciton states in quantum dots using phonon-assisted dissipation, validated by experiments and Bloch-Redfield theory simulations.

Contribution

It introduces a method leveraging phonon-mediated dissipation for efficient exciton and biexciton state preparation in quantum dots, outperforming traditional Rabi oscillations.

Findings

Achieved ≥70% fidelity in exciton preparation using large-area optical pulses.

Mapped exciton-phonon spectral density via laser detuning.

Demonstrated >80% fidelity in biexciton preparation through phonon-assisted processes.

Abstract

Pulsed resonant fluorescence is used to probe ultrafast phonon-assisted exciton and biexciton preparation in individual self-assembled InGaAs quantum dots. By driving the system using large area ($\geq10\pi$) near resonant optical pulses, we experimentally demonstrate how phonon mediated dissipation within the manifold of dressed excitonic states can be used to prepare the neutral exciton with a fidelity $\geq 70\%$. By comparing the phonon-assisted preparation with resonant Rabi oscillations we show that the phonon-mediated process provides the higher fidelity preparation for large pulse areas and is less sensitive to pulse area variations. Moreover, by detuning the laser with respect to the exciton transition we map out the spectral density for exciton coupling to the bulk LA-phonon continuum. Similar phonon mediated processes are shown to facilitate direct biexciton preparation via two photon biexciton absorption, with fidelities $>80\%$. Our results are found to be in very good quantitative agreement with simulations that model the quantum dot-phonon bath interactions with Bloch-Redfield theory.