Not yet reviewed by Pith; the record is open.

Landauer's principle has seen a boom of interest in the last few years due to the growing interest in quantum information sciences. However, its relevance and validity in the contexts of quantum field theory (QFT) remain surprisingly unexplored. In the present paper, we consider Landauer's principle in qubit-cavity QFT interaction perturbatively, in which the initial state of the cavity QFT is chosen to be a vacuum or thermal state. In the vacuum case, the QFT always absorbs heat and jumps to excited states. For the qubit at rest, its entropy decreases, whereas if the qubit accelerates, it may also gain energy and it increases its entropy due to the Unruh effect. For the thermal state, the QFT can both absorb and release heat, depending on its temperature and the initial state of the qubit, and the higher-order perturbations can excite or deexcite the initial state to a higher or lower state. Landauer's principle is valid in all the cases we consider. We hope that this paper will pave the way for future explorations of Landauer's principle in QFT and gravity theories.