  We study the notion of quantum Kac's chaos which was implicitly introduced by
Spohn and explicitly formulated by Gottlieb. We prove the analogue of a result
of Sznitman which gives the equivalence of Kac's chaos to 2-chaoticity and to
convergence of empirical measures. Finally we give a simple, different proof of
a result of Spohn which states that chaos propagates with respect to certain
Hamiltonians that define the evolution of the mean field limit for interacting
quantum systems.
