  Quantum simulation algorithms often require numerous ancilla qubits and deep
circuits, prohibitive for near-term hardware. We introduce a framework for
simulating quantum channels using ensembles of low-depth circuits in place of
many-qubit dilations. This naturally enables simulations of open systems, which
we demonstrate by preparing damped many-qubit GHZ states on ibm_hanoi. The
technique further inspires two Hamiltonian simulation algorithms with
asymptotic independence of the spectral precision, reducing resource
requirements by several orders of magnitude for a benchmark system.
