  We argue that QCD belongs to a topologically ordered phase similar to many
well-known condensed matter systems with a gap such as topological insulators
or superconductors. Our arguments are based on an analysis of the so-called
"deformed QCD" which is a weakly coupled gauge theory, but nevertheless
preserves all the crucial elements of strongly interacting QCD, including
confinement, nontrivial $\theta$ dependence, degeneracy of the topological
sectors, etc. Specifically, we construct the so-called topological "BF" action
which reproduces the well known infrared features of the theory such as
non-dispersive contribution to the topological susceptibility which can not be
associated with any propagating degrees of freedom. Furthermore, we interpret
the well known resolution of the celebrated $U(1)_A$ problem where the would be
$\eta'$ Goldstone boson generates its mass as a result of mixing of the
Goldstone field with a topological auxiliary field characterizing the system.
We then identify the non-propagating auxiliary topological field of the BF
formulation in deformed QCD with the Veneziano ghost (which plays the crucial
role in resolution of the $U(1)_A$ problem). Finally, we elaborate on relation
between "string -net" condensation in topologically ordered condensed matter
systems and long range coherent configurations, the "skeletons", studied in QCD
lattice simulations.
