N-Photon Wave Packets Interacting with an Arbitrary Quantum System

Traveling nonclassical states of light are important resources for quantum metrology, secure communication, and quantum networks. Motivated by this, we derive master equations for an arbitrary quantum system (e.g. a quantum harmonic oscillator or a multi-level atom) interacting with a wavepacket of light prepared in a multimode Fock state. We then generalize this to N-photon states with arbitrary spectral distribution functions and wavepackets in two polarization (or spatial) modes. Our method also allows the calculation of output field quantities. As an illustration of our formalism, we explore the strong coupling regime for an atom in free space and investigate the scattering of multimode Fock states from a two-level atom.