Global quantum discord and matrix product density operators Hai-Lin Huang, Hong-Guang Cheng, Xiao Guo, Duo Zhang, Yuyin Wu, Jian Xu and Zhao-Yu Sun Eur. Phys. J. B, 91 6 (2018) 117 Published online: 13 June 2018 DOI: 10.1140/epjb/e2018-80691-x