Large-Scale Tree-Type Photonic Cluster State Generation with Recurrent Quantum Photonic Neural Networks

TL;DR

This paper introduces a novel recurrent quantum photonic neural network architecture for scalable generation of large, entangled photon cluster states, overcoming limitations of previous methods and enabling advanced quantum network applications.

Contribution

The paper presents a new QPNN-based protocol for generating large tree-type photonic cluster states with high fidelity, scalable beyond current limitations, and applicable to quantum networks.

Findings

QPNN can generate 60-photon clusters with current photonics technology.

The approach achieves near-perfect fidelity despite component imperfections.

Losses limit cluster size, but modest improvements can reach hundreds of photons.

Abstract

Large, multi-dimensional clusters of entangled photons are among the most powerful resources for emerging quantum technologies, as they are predicted to enable global quantum networks or universal quantum computation. Here, we propose an entirely new architecture and protocol for their generation based on recurrent quantum photonic neural networks (QPNNs) and focusing on tree-type cluster states. Unlike other approaches, QPNN-based generators are not limited by the the coherence of quantum emitters or by probabilistic multi-photon operations, enabling arbitrary scaling only limited by loss (which, unavoidably, also affects all other methods). We show that a single QPNN can learn to perform all of the many different operations needed to create a cluster state, from photon routing to entanglement generation, all with near-perfect fidelity and at loss-limited rates, even when it is created from imperfect photonic components. Although these losses ultimately place a limit on the size of the cluster states, we show that state-of-the-art photonics should already allow for clusters of 60 photons, which can grow into the 100s with modest improvements to losses. Finally, we present an analysis of a one-way quantum repeater based on these states, determining the requisite platform quality for a global quantum network and highlighting the potential of the QPNN to play a vital role in high-impact quantum technologies.