Entanglement content of quantum particle excitations

In this talk, I will review the results of recent work in collaboration with Olalla Castro-Alvaredo, Cecilia De Fazio, and Benjamin Doyon. We studied entanglement measures of excited states consisting of a finite number of particle excitations in free massive QFTs. More precisely, we studied the increment of the entanglement entropy and logarithmic negativity due to the presence of excited states, compared to the ground state. We originally studied this problem in massive 1+1 dimensional QFTs where analytic and numerical computations were possible. We have found the result to have a simple qubit interpretation and to apply more widely, including to higher dimensional free theories, and to some interacting situations as well. I will highlight the main QFT techniques that we have used and present some numerical data.