Evolution of entanglement within classical light states

TL;DR

This paper demonstrates that photon pairs emitted by quantum dots exhibit time-dependent entanglement oscillations, revealing their quantum nature and challenging previous classical correlation assumptions.

Contribution

It provides experimental evidence and theoretical explanation for the time-evolving entanglement in photon pairs from quantum dots with finite polarization splitting.

Findings

Photon pairs show oscillating entanglement fidelity over time.

Entanglement is due to phase evolution in the intermediate state.

Quantum dot emission is inherently entangled, not classically correlated.

Abstract

We investigate the evolution of quantum correlations over the lifetime of a multi-photon state. Measurements reveal time-dependent oscillations of the entanglement fidelity for photon pairs created by a single semiconductor quantum dot. The oscillations are attributed to the phase acquired in the intermediate, non-degenerate, exciton-photon state and are consistent with simulations. We conclude that emission of photon pairs by a typical quantum dot with finite polarisation splitting is in fact entangled in a time-evolving state, and not classically correlated as previously regarded.