Decoherence of Rabi oscillations in a single quantum dot

TL;DR

This paper presents a detailed model of Rabi oscillations in quantum-dot photodiodes, revealing the importance of multi-level effects and off-resonant excitations in understanding decoherence and experimental results.

Contribution

It introduces a multi-exciton density matrix model that accounts for higher levels and off-resonant effects, improving the understanding of decoherence in quantum dots.

Findings

Short pulses require multi-level models for accuracy.

Damping is caused by off-resonant excitation to wetting layer states.

Constant rate models cannot explain the observed damping.

Abstract

We develop a realistic model of Rabi oscillations in a quantum-dot photodiode. Based in a multi-exciton density matrix formulation we show that for short pulses the two-level models fails and higher levels should be taken into account. This affects some of the experimental conclusions, such as the inferred efficiency of the state rotation (population inversion) and the deduced value of the dipole interaction. We also show that the damping observed cannot be explained using \emph{constant} rates with fixed pulse duration. We demonstrate that the damping observed is in fact induced by an off-resonant excitation to or from the continuum of wetting layer states. Our model describes the nonlinear decoherence behavior observed in recent experiments.