  Lattice gauge theory should be able to address significant new scientific
questions when implemented on quantum computers. In practice, error-mitigation
techniques have already allowed encouraging progress on small lattices. In this
work we focus on a truncated version of SU(2) gauge theory, which is a familiar
non-Abelian step toward quantum chromodynamics. First, we demonstrate effective
error mitigation for imaginary time evolution on a lattice having two square
plaquettes, obtaining the ground state using an IBM quantum computer and
observing that this would have been impossible without error mitigation. Then
we propose the triamond lattice as an expedient approach to lattice gauge
theories in three spatial dimensions and we derive the Hamiltonian. Finally,
error-mitigated imaginary time evolution is applied to the three-dimensional
triamond unit cell, and its ground state is obtained from an IBM quantum
computer. Future work will want to relax the truncation on the gauge fields,
and the triamond lattice is increasingly valuable for such studies.
