# On-demand source of maximally entangled photon-pairs using the biexciton-exciton radiative cascade

## TL;DR

This paper demonstrates a method to generate on-demand, maximally entangled photon pairs from a semiconductor quantum dot using a biexciton-exciton radiative cascade, with entanglement quality depending on temporal resolution.

## Contribution

It provides a deterministic initiation of biexciton states and full tomographic measurement showing maximal entanglement of emitted photon pairs.

## Key findings

- Photon pairs are maximally entangled during the cascade.
- Entanglement degree depends on temporal resolution.
- Method enables on-demand entangled photon source.

## Abstract

We perform full time resolved tomographic measurements of the polarization state of pairs of photons emitted during the radiative cascade of the confined biexciton in a semiconductor quantum dot. The biexciton was deterministically initiated using a $\pi$-area pulse into the biexciton two-photon absorption resonance. Our measurements demonstrate that the polarization states of the emitted photon pair are maximally entangled. We show that the measured degree of entanglement depends solely on the temporal resolution by which the time difference between the emissions of the photon pair is determined. A route for fabricating an on demand source of maximally polarization entangled photon pairs is thereby provided.