Global quantum discord and matrix product density operatorsHai-Lin Huang, Hong-Guang Cheng, Xiao Guo, Duo Zhang, Yuyin Wu, Jian Xu and Zhao-Yu SunEur. Phys. J. B, 91 6 (2018) 117DOI: https://doi.org/10.1140/epjb/e2018-80691-x