  Simulating physical systems on quantum devices is one of the most promising
applications of quantum technology. Current quantum approaches to simulating
open quantum systems are still practically challenging on NISQ-era devices,
because they typically require ancilla qubits and extensive controlled
sequences. In this work, we propose a hybrid quantum-classical approach for
simulating a class of open system dynamics called random-unitary channels.
These channels naturally decompose into a series of convex unitary evolutions,
which can then be efficiently sampled and run as independent circuits. The
method does not require deep ancilla frameworks and thus can be implemented
with lower noise costs. We implement simulations of open quantum systems up to
dozens of qubits and with large channel rank.
