Preheat the broiler. Place the pitas on a baking sheet and broil 4-5 inches from heat source until golden, about 45 seconds per side. Carefully remove the pan, leaving the broiler on.
Spread 3 tablespoons of hummus, almost to the edge, evenly onto each pita. Place the chicken on top of the hummus, sprinkle with cheese, and top with olives. Broil both pizzas until the cheese melts, about 50-70 seconds.