Measurement of the concurrence of arbitrary two-photon six-qubit hyperentangled state Sha Zhu, Yu-Chen Liu, Bao-Kui Zhao, Lan Zhou, Wei Zhong and Yu-Bo Sheng EPL, 129 5 (2020) 50004 Published online: 08 April 2020 DOI: 10.1209/0295-5075/129/50004