  We perform the real-time lattice simulation of an open quantum system, which
is based on the Schwinger-Keldysh path integral representation of the Lindblad
formalism. Although the real-time simulation generally suffers from the sign
problem, there exist a few exceptional cases. We focus on a sign-problem-free
system of a non-relativistic spinless fermion and analyze time evolution under
driving and dissipation.
