Entangling a Hole Spin with a Time-Bin Photon: A Waveguide Approach for Quantum Dot Sources of Multi-Photon Entanglement

TL;DR

This paper presents a scalable solid-state quantum dot source capable of generating multi-photon entanglement in time-bin encoding, achieving high fidelity and photon indistinguishability for quantum information applications.

Contribution

The authors demonstrate a novel waveguide-based approach for entangling a hole spin with a time-bin photon, enabling scalable multi-photon entanglement from quantum dots.

Findings

Achieved 67.8% fidelity in spin-photon Bell state measurement.

Demonstrated 95.7% photon indistinguishability with resonant excitation.

Proposed steps for further improvements in entanglement quality.

Abstract

Deterministic sources of multi-photon entanglement are highly attractive for quantum information processing but are challenging to realize experimentally. In this paper, we demonstrate a route towards a scaleable source of time-bin encoded Greenberger-Horne-Zeilinger and linear cluster states from a solid-state quantum dot embedded in a nanophotonic crystal waveguide. By utilizing a self-stabilizing double-pass interferometer, we measure a spin-photon Bell state with $(67.8\pm0.4)\%$ fidelity and devise steps for significant further improvements. By employing strict resonant excitation, we demonstrate a photon indistinguishability of $(95.7\pm0.8)\%$, which is conducive to fusion of multiple cluster states for scaling up the technology and producing more general graph states.