  We present the Hamiltonian formulation of a relativistic point-particle
coupled to Einstein gravity and its canonical quantization \`a la
Wheeler-DeWitt. In the resulting quantum theory, the wave functional is a
function of the particle coordinates and the 3-metric. It satisfies a
particular Hamiltonian and diffeomorphism constraint, together with a
Klein-Gordon-type equation. As usual in the Wheeler-DeWitt theory, the wave
function is time-independent. This is also reflected in the Klein-Gordon-type
equation, where the time derivative is absent. Before considering gravity, we
consider the coupling of a particle with electromagnetism, which is treated
similarly, but simpler.
