  We present an experimental analysis of quadrature entanglement produced from
a pair of amplitude squeezed beams. The correlation matrix of the state is
characterized within a set of reasonable assumptions, and the strength of the
entanglement is gauged using measures of the degree of inseparability and the
degree of EPR paradox. We introduce controlled decoherence in the form of
optical loss to the entangled state, and demonstrate qualitative differences in
the response of the degrees of inseparability and EPR paradox to this loss. The
entanglement is represented on a photon number diagram that provides an
intuitive and physically relevant description of the state. We calculate
efficacy contours for several quantum information protocols on this diagram,
and use them to predict the effectiveness of our entanglement in those
protocols.
