The realization of on-chip quantum gates between photons and solid-state spins is a key building block for quantum-information processors, enabling, e.g., distributed quantum computing, where remote quantum registers are interconnected by flying photons. Self-assembled quantum dots integrated in nanostructures are one of the most promising systems for such an endeavor thanks to their near-unity photon-emitter coupling and fast spontaneous emission rate. Here we demonstrate an on-chip entangling gate between an incoming photon and a stationary quantum-dot spin qubit. The gate is based on sequential scattering of a time-bin encoded photon with a waveguide-embedded quantum dot and operates on sub-microsecond timescale; two orders of magnitude faster than other platforms. Heralding on detection of a reflected photon renders the gate fidelity fully immune to spectral wandering of the emitter. These results represent a major step in realizing a quantum node capable of both photonic entanglement generation and on-chip quantum logic, as demanded in quantum networks and quantum repeaters.
@article{arxiv.2205.12844,
title = {On-chip spin-photon entanglement based on single-photon scattering},
author = {Ming Lai Chan and Alexey Tiranov and Martin Hayhurst Appel and Ying Wang and Leonardo Midolo and Sven Scholz and Andreas D. Wieck and Arne Ludwig and Anders Søndberg Sørensen and Peter Lodahl},
journal= {arXiv preprint arXiv:2205.12844},
year = {2023}
}
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Published version. Popular summary: https://physicscommunity.nature.com/posts/creating-light-matter-entanglement-on-a-chip