# Passive demultiplexed two-photon state generation from a quantum dot

## TL;DR

This paper introduces a new passive method to generate two-photon states from a quantum dot, improving the efficiency and scalability of photonic quantum computing.

## Contribution

A novel passive demultiplexing technique using stimulated two-photon excitation is introduced, eliminating the need for active switching elements.

## Key findings

- The passive demultiplexing method achieves switching rates limited only by the quantum dot lifetime.
- Two-photon states are successfully generated from a single quantum dot without active switching elements.
- The method doubles the multi-photon generation rate when combined with active demultiplexing techniques.

## 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 to 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 only limited by the quantum dot lifetime. We demonstrate this method by generating two-photon states from a single quantum dot without requiring 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.