  This thesis collects my own and collaborative work I have been involved with
finding localised systems in quantum field theory that are useful for quantum
information. It draws from many well established physical theories such as
quantum field theory in curved spacetimes, quantum optics and Gaussian state
quantum information. The results are split between three chapters. For the
first results, we set-up the basic framework for working with quantum fields
confined to cavities. By considering the real Klein-Gordon field, we describe
how to model the non-uniform motion of a rigid cavity through spacetime. We
employ the use of Bogoliubov transformations to describe the effects of
changing acceleration. The second set of results investigate how the Dirac
field can be confined to a cavity for quantum information purposes. By again
considering Bogoliubov transformations, we thoroughly investigate how the
entanglement shared between two cavities is affected by non-uniform motion. It
is shown that different types of Dirac field states are more robust against
motion than others. The final results look at using our second notion of
localisation, Unruh- DeWitt detectors. We investigate how allowing for a
"non-point-like" spatial profile of the Unruh-DeWitt detector affects how it
interacts with a quantum field around it. By engineering suitable
detector-field interactions, we use techniques from symplectic geometry to
compute the dynamics of a quantum state beyond commonly used perturbation
theory. There is also a conclusions chapter at the end of the thesis which
summarises the results presented and suggestions of possible new directions of
research in relativistic quantum information are made.
