  Deconfined quark matter at asymptotically high densities is weakly coupled,
due to the asymptotic freedom of Quantum Chromodynamics. In this weak-coupling
regime, bulk thermodynamic properties of quark matter, assuming a trivial
ground state, are currently known to partial next-to-next-to-next-to-leading
order. However, the ground state at high densities is expected to be a color
superconductor, in which the excitation spectrum of (at least some) quarks
exhibit a gap with a non-perturbative dependence on the strong coupling. In
this work, we calculate the thermodynamic properties of color-superconducting
quark matter at high densities and zero temperature at next-to-leading order
(NLO) in the coupling in the presence of a finite gap. We work in the limit of
two massless quark flavors, which corresponds to deconfined symmetric nuclear
matter, and further assume that the gap is small compared to the quark chemical
potential. In these limits, we find that the NLO corrections to the pressure
and speed of sound are comparable in size to the leading-order effects of the
gap, and further increase both quantities above their values for
non-superconducting quark matter. We also provide a parameterization of the NLO
speed of sound to guide phenomenology in the high-density region, and we
furthermore comment on whether our findings should be expected to extend to the
case of three-flavor quark matter of relevance to neutron stars.
