  Obtaining the total wavefunction evolution of interacting quantum systems
provides access to important properties, such as entanglement, shedding light
on fundamental aspects, e.g. quantum energetics and thermodynamics, and guiding
towards possible application in the fields of quantum computation and
communication. We consider a two-level atom (qubit) coupled to the continuum of
travelling modes of a field confined in a one-dimensional waveguide.
Originally, we treat the light-matter ensemble as a closed, isolated system. We
solve its dynamics using a collision model where individual temporal modes of
the field locally interact with the qubit in a sequential fashion. This
approach allows us to obtain the total wavefunction of the qubit-field system,
at any time, when the field starts in a coherent or a single-photon state. Our
method is general and can be applied to other initial field states.
