Using ultra-bright sources of pure-state entangled photons from parametric down conversion, an eight-photon interferometer and post-selection detection, we demonstrate the ability to experimentally manipulate eight individual photons and report the creation of an eight-photon Schr\"odinger cat state with an observed fidelity of 0.708±0.016.
@article{arxiv.1105.6318,
title = {Observation of eight-photon entanglement},
author = {Xing-Can Yao and Tian-Xiong Wang and Ping Xu and He Lu and Ge-Sheng Pan and Xiao-Hui Bao and Cheng-Zhi Peng and Chao-Yang Lu and Yu-Ao Chen and Jian-Wei Pan},
journal= {arXiv preprint arXiv:1105.6318},
year = {2015}
}