Shortcoming of spectral filtering in semiconductor-based entangled photon sources

TL;DR

This paper analyzes the limitations of spectral filtering in generating high-quality polarization-entangled photons from semiconductor quantum dots, highlighting how dephasing processes reduce entanglement despite filtering efforts.

Contribution

It reveals that spectral filtering schemes are fundamentally limited by dephasing in solid-state systems, affecting entanglement quality.

Findings

Filtering does not fully recover entanglement due to dephasing.

Dephasing processes deteriorate photon state quality.

Spectral filtering alone is insufficient for high entanglement.

Abstract

We theoretically investigate the production of polarization-entangled photons through the biexciton cascade decay in a single semiconductor quantum dot. To accomplish a high degree of entanglement, despite the exciton finestructure splitting, one must either energetically align the two exciton states by means of external fields or erase the which-path information by post-selecting photons within the correct frequency range. Here we show that in the latter scheme, as well as in related proposals, the photon state becomes deteriorated through dephasing processes in the solid, and the degree of entanglement remains low despite filtering.