  To explain the production of light nuclei in heavy-ion collisions at extreme
energies, we focus on the deuteron case. A Gibbs ensemble at chemical
freeze-out is a prerequisite to investigate the non-equilibrium evolution of
the expanding fireball. Quantum statistical approaches allow to describe
correlations including bound state formation in the strongly interacting and
hot system. We consider the virial approach to evaluate proton-neutron
correlations. In generalization of the treatment of protons in pionic matter
(pion-proton puzzle), the influence of the pion environment on deuteron-like
correlations is evaluated using data for the pion-deuteron scattering phase
shifts. Calculated yields for deuteron production are compared with the ones
observed at the LHC.
