  Uncertainties in the frequency parameters of a frequency comb laser, causes
it to represent a mixed quantum state. The formulation of such a quantum state
is compounded by the fact that it contains both particle-number degrees of
freedom and temporal degrees of freedom. Here we develop a formalism in terms
of which such a mixed quantum state can be expressed. For this purpose we also
need to compute the expression for the power spectral density of the frequency
comb laser. We do so by taking the uncertainties in the frequency parameters
into account.
