Forster signatures and qubits in optically driven quantum dot molecules

TL;DR

This paper models exciton dynamics in quantum dot molecules under laser excitation and electric fields, revealing signatures of Forster energy transfer and proposing a method for exciton qubit rotations via adiabatic electric field sweeps.

Contribution

It introduces a realistic model for exciton dynamics in quantum dot molecules and demonstrates a novel approach for exciton qubit manipulation using electric field sweeps.

Findings

Identification of excitonic anticrossings and dipole-dipole Forster transfer signatures.

Observation of Rabi oscillations in exciton qubits during electric field sweeps.

Rich structure in dressed ground state maps indicating relevant couplings.

Abstract

An interesting approach to achieve quantum gate operations in a solid state device is to implement an optically driven quantum gate using two vertically coupled self-assembled quantum dots, a quantum dot molecule (QDM). We present a realistic model for exciton dynamics in InGaAs/GaAs QDMs under intense laser excitation and applied electric fields. The dynamics is obtained by solutions of the Lindblad master equation. A map of the dressed ground state as function of laser energy and applied electric field exhibits rich structure that includes excitonic anticrossings that permit the identification of the relevant couplings. The optical signatures of the dipole-dipole Forster energy transfer mechanism show as splittings of several (spatially) indirect excitonic lines. Moreover, we construct a model for exciton qubit rotations by adiabatic electric field cyclic sweeps into a Forster-tunneling regime which induces level anticrossings. The proposed qubit exhibits Rabi oscillations among two well defined exciton pairs as function of the residence time at the anticrossing.