  Ca3Co2O6 is a frustrated magnet consisting of a triangular arrangement of
chains of Ising spins. It shows regular magnetization steps vs magnetic field
every 1.2 T that are metastable with very slow dynamics. This has puzzled the
community for many years and given rise to numerous potential theories. Here we
approach the problem by seeking the elusive magnetic equilibrium state at T = 2
K. To this end, we explore two approaches: (1) bypassing the slow dynamics
produced by changing fields by instead field-cooling directly to the target
temperature, and (2) quantum annealing in transverse magnetic fields. While we
observe no measurable effect of the quantum annealing in fields up to 7 T,
which is likely due to the large Ising anisotropy of Co spins in this material,
we find that for the field cooling in longitudinal fields we achieve the
predicted equilibrium 1/3 magnetization. We perform Monte Carlo simulations of
the ground state phase diagram and we also simulate the quantum annealing
process and find good agreement between experiment and theory. Thus we present
an investigation of the elusive ground state properties of the canonical
frustrated triangular system Ca3Co2O6.
