  In this work we construct Wigner functions for hybrid continuous and discrete
variable quantum systems. We demonstrate new capabilities in the visualization
of the interactions and correlations within hybrid quantum systems.
Specifically, we show how to clearly distinguish signatures that arise due to
quantum and classical correlations in an entangled Bell-cat state. We further
show how correlations are manifested in different types of interaction, leading
to a deeper understanding of how quantum information is shared between two
subsystems. Understanding the nature of the correlations between systems is
central to harnessing quantum effects for information processing; the methods
presented here reveal the nature of these correlations, allowing a clear
visualization of the quantum information present in hybrid quantum systems. The
methods presented here could be viewed as a form of quantum state spectroscopy.
