Formation dynamics of an entangled photon pair -- a temperature dependent analysis

TL;DR

This paper provides a theoretical analysis of how temperature affects the polarization entanglement of photon pairs generated in semiconductor quantum dots, highlighting the temperature thresholds where entanglement degrades and is lost.

Contribution

It introduces a detailed theoretical model including phonon interactions and temperature effects to analyze entanglement dynamics in quantum dot photon sources.

Findings

Entanglement degrades with increasing temperature.

Entanglement is lost above approximately 120 K.

Phonon interactions significantly influence entanglement dynamics.

Abstract

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.