We theoretically study the polarization entanglement of photons generated by the biexciton cascade in a GaAs/InAs semiconductor quantum dot (QD), located in a nano cavity. A detailed analysis of the complex interplay between photon- and carrier coherences and phonons which occurs during the cascade allows us to clearly identify where the entanglement is generated and destroyed. A quantum state tomography is performed for varying exciton fine structure splittings. By constructing an effective multi-phonon Hamiltonian which couples the continuum of the wetting layer states to the QD we investigate the relaxation of the biexciton and exciton states. This consistently introduces a temperature dependence to the cascade. Considering typical Stranski-Karastanov grown QDs, for temperatures around 80 K the degree of entanglement starts to be affected by the dephasing of the exciton states and is ultimately lost above 120 K.
@article{arxiv.0910.5445,
title = {Formation dynamics of an entangled photon pair -- a temperature dependent analysis},
author = {A. Carmele and F. Milde and M. -R. Dachner and M. Bagheri Harouni and R. Rokniknizadeh and M. Richter and A. Knorr},
journal= {arXiv preprint arXiv:0910.5445},
year = {2013}
}
Comments
14 pages, 10 figures, 1 table, submitted to phys. rev. B