  We recall the framework of a consistent quantum description of polarization
of light. Accordingly, the degree of polarization of a two-mode state $\hat
\rho$ of the quantum radiation field can be defined as a distance of a related
state ${\hat \rho}_b$ to the convex set of all SU(2) invariant two-mode states.
We explore a distance-type polarization measure in terms of the quantum
Chernoff bound and derive its explicit expression. A comparison between the
Chernoff and Bures degrees of polarization leads to interesting conclusions for
some particular states chosen as illustrative examples.
