quantum optics is a reference to a "c-number" Hi In my lecture notes on quantum optics is a reference to a "c-number" electric field, and it is stated that, since it is a c-number, there is no corresponding Hamiltonian. As far as I have understood, a c-number is a classical value of some (possibly quantum mechanical) quantity. However, how can this rule out that the c-number has a Hamiltonian? E.g., a classical electric field has a well-defined Hamiltonian given by its energy density. Best, Niles.