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

Martin Hayhurst Appel, Alexey Tiranov, Simon Pabst, Ming Lai Chan, Christian Starup, Ying Wang, Leonardo Midolo, Konstantin Tiurev, Sven Scholz, Andreas D. Wieck, Arne Ludwig, Anders Søndberg Sørensen, Peter Lodahl
Phys. Rev. Lett. 128, 233602 (2022)

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±0.4)% fidelity and devise steps for significant further improvements. By employing strict resonant excitation, we demonstrate a photon indistinguishability of (95.7±0.8)%, which is conducive to fusion of multiple cluster states for scaling up the technology and producing more general graph states.