Passive Demultiplexed Two-photon State Generation from a Quantum Dot

TL;DR

This paper presents a passive, stimulated two-photon excitation method for quantum dots that enables loss-free, high-rate multi-photon state generation without active switching, advancing scalable photonic quantum computing.

Contribution

It introduces a passive demultiplexing technique using stimulated two-photon excitation, eliminating the need for active switching elements in multi-photon generation from quantum dots.

Findings

Demonstrated two-photon state generation without active switches.

Achieved higher multi-photon rates limited only by quantum dot lifetime.

Reduced demultiplexing costs and complexity.

Abstract

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.