Non-local correlation and quantum discord in two atoms in the non-degenerate model

By using geometric quantum discord (GQD) and measurement-induced nonlocality (MIN), quantum correlation is investigated for two atoms in the non-degenerate two-photon Tavis–Cummings model. It is shown that there is no asymptotic decay for MIN while asymptotic decay exists for GQD. Quantum correlations can be strengthened by introducing the dipole–dipole interaction. The evolvement period of quantum correlation gets shorter with the increase in the dipole–dipole parameter. It is found that there exists not only quantum nonlocality without entanglement but also quantum nonlocality without quantum discord. Also, the MIN and GQD are raised rather than entanglement, and also with weak initial entanglement, there are MIN and entanglement in a interval of death quantum discord.

► Geometric quantum discord (GQD) and measurement induced nonlocality (MIN) are used to investigate the correlations of two two-level atoms.
► There is no asymptotic decay for MIN while asymptotic decay exists for GQD.
► Quantum correlations can be strengthened by introducing the dipole–dipole interaction.
► There exists not only quantum nonlocality without entanglement but also without discord.
► Weak initial entanglement leads to MIN and entanglement in intervals of death discord.