  Many-body localization (MBL) addresses the absence of thermalization in
interacting quantum systems, with non-ergodic high-energy eigenstates behaving
as ground states, only area-law entangled. However, computing highly excited
many-body eigenstates using exact methods is very challenging. Instead, we show
that one can address high-energy MBL physics using ground-state methods, which
are much more amenable to many efficient algorithms. We find that a localized
many-body ground state of a given interacting disordered Hamiltonian
$\mathcal{H}_0$ is a very good approximation for a high-energy eigenstate of a
parent Hamiltonian, close to $\mathcal{H}_0$ but more disordered. This
construction relies on computing the covariance matrix, easily achieved using
density-matrix renormalization group for disordered Heisenberg chains up to
$L=256$ sites.
