Prospects for photon blockade in four-level systems in the N configuration with more than one atom

We show that for appropriate choices of parameters it is possible to achieve photon blockade in idealized one-, two- and three-atom systems. We also include realistic parameter ranges for rubidium as the atomic species. Our results circumvent the doubts cast by recent discussion in the literature (Grangier et al 1998 Phys. Rev. Lett. 81 2833, Imamoglu ct al 1998 Phys. Rev. Lett. 81 2836) on the possibility of photon blockade in multi-atom systems.