In this talk, I would present our recent work (arXiv:2001.00485) on digital quantum simulation of 1+1 dimensional quantum electrodynamics (Schwinger model) with the topological term, using adiabatic state preparation. This, in turn, allows us to compute an expectation value of the fermion mass operator with respect to the vacuum. We estimate computational costs required to take reasonable continuum and thermodynamic limits. Our results imply that digital quantum simulation is already useful tool to explore non-perturbative aspects of gauge theories with real time and topological terms.