  We introduce multinode quantum trajectory simulations with qsim, an open
source high performance simulator of quantum circuits. qsim can be used as a
backend of Cirq, a Python software library for writing quantum circuits. We
present a novel delayed inner product algorithm for quantum trajectories which
can result in an order of magnitude speedup for low noise simulation. We also
provide tools to use this framework in Google Cloud Platform, with high
performance virtual machines in a single mode or multinode setting. Multinode
configurations are well suited to simulate noisy quantum circuits with quantum
trajectories. Finally, we introduce an approximate noise model for Google's
experimental quantum computing platform and compare the results of noisy
simulations with experiments for several quantum algorithms on Google's Quantum
Computing Service.
