  We calculate the total cross section for the scattering of a
quark--anti-quark dipole on a large nucleus at high energy for a strongly
coupled N=4 super Yang-Mills theory using AdS/CFT correspondence. We model the
nucleus by a metric of a shock wave in AdS_5. We then calculate the expectation
value of the Wilson loop (the dipole) by finding the extrema of the Nambu-Goto
action for an open string attached to the quark and antiquark lines of the loop
in the background of an AdS_5 shock wave. We find two physically meaningful
extremal string configurations. For both solutions we obtain the forward
scattering amplitude N for the quark dipole--nucleus scattering. We study the
onset of unitarity with increasing center-of-mass energy and transverse size of
the dipole: we observe that for both solutions the saturation scale Q_s is
independent of energy/Bjorken-x and depends on the atomic number of the nucleus
as Q_s ~ A^{1/3}. Finally we observe that while one of the solutions we found
corresponds to the pomeron intercept of \alpha_P = 2 found earlier in the
literature, when extended to higher energy or larger dipole sizes it violates
the black disk limit. The other solution we found respects the black disk limit
and yields the pomeron intercept of \alpha_P = 1.5. We thus conjecture that the
right pomeron intercept in gauge theories at strong coupling may be \alpha_P =
1.5.
