  Recent years have seen unprecedented advance in the design and control of
quantum computers. Nonetheless, their applicability is still restricted and
access remains expensive. Therefore, a substantial amount of quantum algorithms
research still relies on simulating quantum circuits on classical hardware.
However, due to the sheer complexity of simulating real quantum computers, many
simulators unrealistically simplify the problem and instead simulate perfect
quantum hardware, i.e., they do not consider errors caused by the fragile
nature of quantum systems. Stochastic quantum simulation provides a
conceptually suitable solution to this problem: physically motivated errors are
applied in a probabilistic fashion throughout the simulation. In this work, we
propose to use decision diagrams, as well as concurrent executions, to
substantially reduce resource-requirements-which are still daunting-for
stochastic quantum circuit simulation. Backed up by rigorous theory, empirical
studies show that this approach allows for a substantially faster and much more
scalable simulation for certain quantum circuits.
