Distilling entanglement from cascades with partial "Which Path" ambiguity

TL;DR

This paper presents a framework for calculating the entanglement of photon pairs emitted in decay cascades with partial path ambiguity, and demonstrates its application to quantum dots with experimental validation.

Contribution

It introduces a new theoretical framework and entanglement distillation scheme for cascades with partial path ambiguity, validated through quantum dot experiments.

Findings

Effective entanglement distillation for certain random cascades.

Qualitative phase diagram of entanglement features.

Agreement between theory and quantum dot experiment.

Abstract

We develop a framework to calculate the density matrix of a pair of photons emitted in a decay cascade with partial "which path" ambiguity. We describe an appropriate entanglement distillation scheme which works also for certain random cascades. The qualitative features of the distilled entanglement are presented in a two dimensional "phase diagram". The theory is applied to the quantum tomography of the decay cascade of a biexciton in a semiconductor quantum dot. Agreement with experiment is obtained.