  We present time-resolved measurements of spin-flip photon-assisted tunneling
and spin-flip relaxation in a doubly occupied double quantum dot. The
photon-assisted excitation rate as a function of magnetic field indicates that
spin-orbit coupling is the dominant mechanism behind the spin-flip under the
present conditions. We are able to extract the resulting effective `spin-flip
tunneling' energy, which is found to be three orders of magnitude smaller than
the regular spin-conserving tunneling energy. We also measure the relaxation
and dephasing times of a qubit formed out of two two-electron states with
different spin and charge configurations.
