On exciton decoherence in quantum dots

TL;DR

This paper analyzes how phonon interactions cause decoherence in excitons within quantum dots, highlighting the energetic shifts and timescales involved, which are crucial for quantum computing applications.

Contribution

It provides a detailed analysis of phonon-induced decoherence mechanisms in quantum dots, emphasizing the roles of optical and acoustic phonons and their impact on quantum gate coherence times.

Findings

Optical phonon dressing causes a few meV energy shift.

Dressing time with optical phonons is about one picosecond.

This timescale sets a lower limit for decoherence in quantum gates.

Abstract

The effects resulting due to dressing of an exciton with phonons are analysed as the source of unavoidable decoherence of orbital degrees of freedom in quantum dots. The dressing with longitudinal optical phonons results in energetic shift of order of a few meV even of the ground state of exciton in a state-of-the-art InAs/GaAs dot and the mediating role of longitudinal acoustical phonons is essential in this process. The characteristic time needed for dressing of the exciton with optical phonons is of a picosecond order. That time can be regarded as the lowest limit for decoherence for optically driven quantum gates employing self-assembled quantum dot structures.