Entanglement between a quantum dot spin and a single optical photon

Atac Imamoglu, Weibo Gao, Parisa Fallahi, Emre Togan, Javier Miguel-Sanchez

Institute of Quantum Electronics, ETH Zurich, Switzerland

We report the observation of entanglement between a single quantum dot spin and the color of a propagating optical photon. The demonstration of entanglement relies on the use of fast single-photon detection which allows us to project the photon into a superposition of its two frequency components. Due to fast optical transitions and favorable selection rules, the scheme we implement generates inherently deterministic entangled spin-photon pairs at an unprecedented rate of 76.3 megahertz; the pair-rate we measure on the other hand is limited by the spin and photon collection/detection efficiencies.