Quantum dots for quantum repeaters

Abstract

This review surveys recent progress in III--V semiconductor quantum dots (QDs) as a platform for quantum repeaters. We start by discussing the state of the art in QD-based non-classical light sources. Specifically, we report on on single-photon and entangled-pair sources operating across near-infrared and telecom wavelengths, with emphasis on the key metrics-multi-photon suppression g2(0), photon indistinguishability, extraction efficiency, and spin coherence time-while discussing frequency conversion, excitation schemes, cavity engineering, remote indistinguishability, and spin coherence. We then examine the two principal repeater architectures. For all-photonic repeaters we review linear cluster- and graph-state generation using QD spins, recent experimental milestones, and the critical role of spin dephasing time. For memory-based repeaters we focus on heterogeneous implementations combining deterministic QD photon sources with room-temperature alkali-vapor memories, providing rate benchmarking against other platforms, discussion of storage protocols, wavelength compatibility, and early demonstrations. Enabling technologies such as cryogenic cooling, on-chip photonic integration, network synchronization and multiplexing are also presented. The review highlights the strength of QD-based architectures and identifies the remaining milestones required for their deployment in practical fiber-based quantum networks.