  We discuss a diagonal representation of a reduced density matrix determined
within the framework of the complex scaling method. We also discuss a possible
measure of bipartite correlations in quantum resonance states. As an example,
we consider a one-dimensional system of two bosons with a contact interaction
subjected to an open potential well. The correlation properties of the
lowest-energy resonance state of the system are explored over a wide range of
the inter-boson interaction strength, including the Tonks-Girardeau regime.
