Classical optical analogue of quantum discordJacob M. Leamer, Wenlei Zhang, Nicholas J. Savino, Ravi K. Saripalli, Sanjaya Lohani, Ryan T. Glasser and Denys I. BondarEur. Phys. J. Spec. Top., 232 20-22 (2023) 3345-3351DOI: https://doi.org/10.1140/epjs/s11734-023-00988-1