  We investigate how entanglement can enhance two-photon absorption in a
three-level system. First, we employ the Schmidt decomposition to determine the
entanglement properties of the optimal two-photon state to drive such a
transition, and the maximum enhancement which can be achieved in comparison to
the optimal classical pulse. We then adapt the optimization problem to
realistic experimental constraints, where photon pairs from a down-conversion
source are manipulated by local operations such as spatial light modulators. We
derive optimal pulse shaping functions to enhance the absorption efficiency,
and compare the maximal enhancement achievable by entanglement to the yield of
optimally shaped, separable pulses.
