Indistinguishable photons from a two-photon cascade

TL;DR

This paper demonstrates high-visibility two-photon interference from a semiconductor quantum dot by enhancing photon coherence through Purcell effect, advancing solid-state entangled photon sources.

Contribution

It shows that Purcell enhancement improves photon coherence in a quantum dot cascade, achieving high interference visibility for both photons.

Findings

High interference visibility for XX (94%) and X (82%) photons.

Photon coherence follows quantum optics predictions with varying lifetime ratios.

Purcell enhancement reduces photon temporal correlation issues.

Abstract

Decay of a four-level diamond scheme via a cascade is a potential source of entangled photon pairs. A solid-state implementation is the biexciton cascade in a semiconductor quantum dot. While high entanglement fidelities have been demonstrated, the two photons, XX and X, are temporally correlated, typically resulting in poor photon coherence. Here, we demonstrate a high two-photon interference visibility (a measure of the photon coherence) for both XX (V=94$\pm$2%) and X (V=82$\pm$6%) photons. This is achieved by Purcell-enhancing the biexciton transition in a low-noise device. We find that the photon coherence follows the well-known quantum optics result upon tuning the XX:X lifetime ratio over two orders of magnitude.