  We demonstrate how a colloidal version of artificial ice can be realized on
optical trap lattices. Using numerical simulations, we show that this system
obeys the ice rules and that for strong colloid-colloid interactions, an
ordered ground state appears. We show that the ice rule ordering can occur for
systems with as few as twenty-four traps and that the ordering transition can
be observed at constant temperature by varying the barrier strength of the
traps.
