  The utility of quantum computers for simulating lattice gauge theories is
currently limited by the noisiness of the physical hardware. Various quantum
error mitigation strategies exist to reduce the statistical and systematic
uncertainties in quantum simulations via improved algorithms and analysis
strategies. We perform quantum simulations of $1+1d$ $\mathbb{Z}_2$ gauge
theory with matter to study the efficacy and interplay of different error
mitigation methods: readout error mitigation, randomized compiling, rescaling,
and dynamical decoupling. We compute Minkowski correlation functions in this
confining gauge theory and extract the mass of the lightest spin-1 state from
fits to their time dependence. Quantum error mitigation extends the range of
times over which our correlation function calculations are accurate by a factor
of six and is therefore essential for obtaining reliable masses.
