High-purity multi-photon states are essential for photonic quantum computing. Among existing platforms, semiconductor quantum dots offer a promising route to scalable and deterministic multi-photon state generation. However, to fully realize their potential we require a suitable optical excitation method. Current approaches of multi-photon generation rely on active polarization-switching elements (e.g., electro-optic modulators, EOMs) to spatio-temporally demultiplex single photons. Yet, the achievable multi-photon rate is fundamentally limited by the switching speed of the EOM. Here, we introduce a fully passive demultiplexing technique that leverages a stimulated two-photon excitation process to achieve switching rates that are only limited by the quantum dot lifetime. We demonstrate this method by generating two-photon states from a single quantum dot without requiring any active switching elements. Our approach significantly reduces the cost of demultiplexing while shifting it to the excitation stage, enabling loss-free demultiplexing and effectively doubling the achievable multi-photon generation rate when combined with existing active demultiplexing techniques.
@article{arxiv.2502.14806,
title = {Passive Demultiplexed Two-photon State Generation from a Quantum Dot},
author = {Yusuf Karli and Iker Avila Arenas and Christian Schimpf and Ailton José Garcia Junior and Santanu Manna and Florian Kappe and René Schwarz and Gabriel Undeutsch and Maximilian Aigner and Melina Peter and Saimon F Covre da Silva and Armando Rastelli and Gregor Weihs and Vikas Remesh},
journal= {arXiv preprint arXiv:2502.14806},
year = {2025}
}