  Phonon-induced spin relaxation in coupled lateral quantum dots in the
presence of spin-orbit coupling is calculated. The calculation for single dots
is consistent with experiment. Spin relaxation in double dots at useful
interdot couplings is dominated by spin hot spots that are strongly
anisotropic. Spin hot spots are ineffective for a diagonal crystallographic
orientation of the dots with a transverse in-plane field. This geometry is
proposed for spin-based quantum information processing.
