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arXiv · 2512.16617

Indistinguishable photons from a two-photon cascade

Timon L. Baltisberger·Francesco Salusti·Mark R. Hogg·Malwina A. Marczak·Nils Heinisch·Sascha R. Valentin·Stefan Schumacher·Arne Ludwig·Klaus D. Jöns·Richard J. Warburton
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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.

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Timon L. Baltisberger, Francesco Salusti, Mark R. Hogg, Malwina A. Marczak, Nils Heinisch, Sascha R. Valentin, Stefan Schumacher, Arne Ludwig, Klaus D. Jöns, Richard J. Warburton. 2025-12-18. Indistinguishable photons from a two-photon cascade. https://doi.org/10.1103/t8sk-b2w4

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