  We report an experimental investigation of momentum diffusion in the
delta-function kicked rotor where time symmetry is broken by a two-period
kicking cycle and spatial symmetry by an alternating linear potential. The
momentum diffusion constant is thus modified by kick-to-kick correlations which
show a momentum dependence. We exploit this, and a technique involving a moving
optical potential, to create an asymmetry in the momentum diffusion that is due
entirely to the chaotic dynamics.
