  Basis Light-front Quantization (BLFQ) is a newly developed nonperturbative
approach, aiming at solving relativistic bound systems based on the Hamiltonian
formalism of light-front dynamics. In this work, we introduce its application
to the positronium system at strong coupling, $\alpha = 0.3$, with a dynamical
photon mediating the interaction between the positron and the electron.
Nonperturbative mass renormalization is needed to cancel the fermion
self-energy divergence. Here, we present the resulting mass spectrum,
light-front wave functions (LFWFs), and the photon distribution inside
positronium.
