The Coulomb solution as a coherent state of unphysical photons

In the context of the problem of what micro-states are responsible for the entropy of black holes, we consider as a physical toy model the electromagnetic Coulomb solution. By quantizing the electromagnetic field in the presence of an external source of charge Q, the quantum state corresponding to the Coulomb solution is identified as a coherent state of longitudinal and temporal photons in a Hilbert space with negative norm states.