  Characterizing and accessing quantum phases of itinerant bosons or fermions
in two dimensions (2D) that exhibit singular structure along surfaces in
momentum space but have no quasi-particle description remains as a central
challenge in the field of strongly correlated physics. Fortuitously, signatures
of such 2D strongly correlated phases are expected to be manifest in
quasi-one-dimensional "$N$-leg ladder" systems. The ladder discretization of
the transverse momentum cuts through the 2D surface, leading to a quasi-1D
descendant state with a set of low-energy modes whose number grows with the
number of legs and whose momenta are inherited from the 2D surfaces. These
multi-mode quasi-1D liquids constitute a new and previously unanticipated class
of quantum states interesting in their own right. But more importantly they
carry a distinctive quasi-1D "fingerprint" of the parent 2D quantum fluid
state. This can be exploited to access the 2D phases from controlled numerical
and analytical studies in quasi-1D models. The preliminary successes and future
prospects in this endeavor will be briefly summarized.
