  We study the effect of a weak magnetic field on the state of the spins of a
pair of electrons forming a Cooper pair in an s-wave superconductor. By
perturbatively solving time-dependent Bogoliubov equations up to first order,
we obtain the two-particle Green function, and whence the two-electron
spin-space density matrix. It appears that up to first order approximation, the
spin state of a Cooper pair retains the form of a Werner state. This state is
then examined in the sense of quantum correlations, i.e., quantum discord.
