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±2%) and X (V=82±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.
@article{arxiv.2512.16617,
title = {Indistinguishable photons from a two-photon cascade},
author = {Timon L. Baltisberger and Francesco Salusti and Mark R. Hogg and Malwina A. Marczak and Nils Heinisch and Sascha R. Valentin and Stefan Schumacher and Arne Ludwig and Klaus D. Jöns and Richard J. Warburton},
journal= {arXiv preprint arXiv:2512.16617},
year = {2025}
}
Comments
10 pages, 4 figures in main paper, 5 figures in supplementary information