Giant Photon Blockade with Multiple Atoms.

Nonlinearity at the single-photon level is important in both fundamental research and applications of quantum optics. Strong single-photon nonlinearity is usually hard to achieve with a single atom coupled to a cavity mode. Unfortunately, stronger nonlinearity cannot be achieved by coupling more atoms straightforwardly because of the gradual homogeneity of the system energy levels. Here we propose two proposals to realize deeper photon blockade with the increase of the atom number with the help of quantum Zeno dynamics. The single-photon blockade that manifests single-photon nonlinearity is achieved with high single-photon efficiency and purity. We developed a hybrid method by partitioning the system states into two subsets with one computed via a master equation and the other via a non-Hermitian Hamiltonian. This method significantly reduces computational resource requirements and enables simulations of systems with up to thousands of atoms. The results show that our proposals are robust against the inhomogeneity of atom frequency and coupling strength, which is favorable in experiments.