Deterministic generation of arbitrary n-photon states in a waveguide-QED system

Quantum light sources play a vital role in various aspects of quantum information science, but on-demand highly efficient generation of arbitrary multiphoton states which can be easily integrated is still challenging. Here, we propose a chip-integrable scheme to deterministically generate a group of n photons with very high fidelity based on the long-range collective interaction between the emitters mediated by the waveguide modes. The n photons are shown to be emitted in a bundle while two successive n-photon bundles tend to be antibunched and can behave as an n-photon gun. Our results here can find applications in areas such as chip-integrated quantum information processing and quantum metrology.