# Active multiplexing for scalable generation and manipulation of photonic quantum states

## TL;DR

This paper reviews how active multiplexing helps overcome challenges in creating and controlling quantum states using photons, enabling scalable quantum computing.

## Contribution

The paper provides a comprehensive overview of recent advancements and architectures in photonic active multiplexing for quantum information processing.

## Key findings

- Active multiplexing enables deterministic quantum operations from probabilistic processes.
- Recent progress includes quasi-deterministic single-photon generation and entangled states.
- Integration of photon sources, detectors, and switches is advancing scalable quantum systems.

## Abstract

Photons serve as essential carriers of quantum information in quantum computing, quantum networking, and quantum metrology. However, the lack of direct photon-photon interaction poses a fundamental barrier: the inherently probabilistic nature of nonlinear quantum operations. Active multiplexing has emerged as the critical strategy, transforming probabilistic nonlinear processes into deterministic building blocks for large-scale quantum systems. In this review, we explore the recent progress and potential architectures of photonic active multiplexing systems, ranging from the quasi-deterministic generation of single photons and complex entangled states to the realization of measurement-based quantum computing architectures. We also provide an overview of recent advancements in enabling hardware—including basic photon sources, detectors, switches, and their integration. By analyzing the state of the art and identifying key remaining challenges, we highlight how active multiplexing strategies serve as the cornerstone for the next generation of scalable photonic quantum information processing.