Polarization-entangled twin photons from two-photon quantum-dot emission

TL;DR

This paper investigates how a high-quality optical cavity enhances polarization-entangled twin photon emission from quantum dots, demonstrating robustness against phonon interactions and analyzing spectral and statistical properties.

Contribution

It provides a detailed analysis of biexciton emission in quantum dots coupled to cavities, highlighting suppression of phonon effects and maintaining high entanglement levels.

Findings

High-quality cavities enable efficient two-photon emission with strong polarization entanglement.

Phonon interactions have limited impact on entanglement when cavity is tuned to half biexciton energy.

Spectral properties and photon statistics are characterized, confirming the robustness of the entangled photon source.

Abstract

Semiconductor quantum dots are promising sources for polarization-entangled photons. As an alternative to the usual cascaded biexciton-exciton emission, direct two-photon emission from the biexciton can be used. With a high-quality optical resonator tuned to half the biexciton energy, a large proportion of the photons can be steered into the two-photon emission channel. In this case the degree of polarization entanglement is inherently insensitive to the exciton fine-structure splitting. In the present work we analyze the biexciton emission with particular emphasis on the influence of coupling of the quantum-dot cavity system to its environment. Especially for a high-quality cavity, the coupling to the surrounding semiconductor material can open up additional phonon-assisted decay channels. Our analysis demonstrates that with the cavity tuned to half the biexciton energy, the potentially detrimental influence of the phonons on the polarization entanglement is strongly suppressed -- high degrees of entanglement can still be achieved. We further discuss spectral properties and statistics of the emitted twin photons.