please see the following Hamiltonian mode.
two two-level atoms(or two qubits) interact with photon.
á、à are the creation and annihilation operators of photon
please rewriting H in the way of pauli operators , will looks very simple
H = E1 ( |e1><e1| －|g1><g1| ) + E2 ( |e2><e2| －|g2><g2|...