  We develop a workflow to use current quantum computing hardware for solving
quantum many-body problems, using the example of the fermionic Hubbard model.
Concretely, we study a four-site Hubbard ring that exhibits a transition from a
product state to an intrinsically interacting ground state as hopping
amplitudes are changed. We locate this transition and solve for the ground
state energy with high quantitative accuracy using a variational quantum
algorithm executed on an IBM quantum computer. Our results are enabled by a
variational ansatz that takes full advantage of the maximal set of commuting
$\mathbb{Z}_2$ symmetries of the problem and a Lanczos-inspired error
mitigation algorithm. They are a benchmark on the way to exploiting near term
quantum simulators for quantum many-body problems.
