Probing electron-phonon interaction through two-photon interference in resonantly driven semiconductor quantum dots

TL;DR

This paper studies how electron-phonon interactions affect photon coherence in quantum dots, revealing two distinct phonon-related decoherence processes that depend on temperature, with implications for quantum information applications.

Contribution

It provides a detailed microscopic theory distinguishing two phonon-induced decoherence mechanisms and their temperature dependence in resonantly driven quantum dots.

Findings

Below 10K, lattice relaxation dominates decoherence.

Above 10K, virtual phonon transitions cause rapid decoherence.

The theory offers analytic expressions for phonon-related dephasing rates.

Abstract

We investigate the temperature dependence of photon coherence properties through two photon interference (TPI) measurements from a single QD under resonant excitation. We show that the loss of indistinguishability is only related to the electron-phonon coupling without being affected by spectral diffusion. Through these measurements, and a complementary microscopic theory, we identify two independent separate decoherence processes each associated to phonons. Below 10K, we find that the relaxation of the vibrational lattice is the dominant contribution to the loss of TPI visibility. This process is non-Markovian in nature, and corresponds to real phonon transitions resulting in a broad phonon sideband in the QD emission spectra. Above 10K, virtual phonon transitions to higher lying excited states in the QD become the dominant dephasing mechanism, this leads to broadening of the zero phonon line, and a corresponding rapid decay in the visibility. The microscopic theory we develop provides analytic expressions for the dephasing rates for both virtual phonon scattering and non-Markovian lattice relaxation.