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 gate counts that are asymptotically independent of the spectral precision target, reducing resource requirements by several orders of magnitude for a benchmark system.

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Nature

A new framework for quantum simulation uses stochastic combinations of unitaries—ensembles of low-depth circuits—to simulate quantum channels without requiring many ancilla qubits or deep circuits. This approach is suitable for near-term hardware and naturally supports open quantum system simulation, demonstrated by preparing damped many-qubit GHZ states on IBM's ibm_hanoi processor. The technique also yields two Hamiltonian simulation algorithms whose gate counts are asymptotically independent of spectral precision, reducing resource requirements by several orders of magnitude compared to benchmark systems.

Quantum simulation via stochastic combination of unitaries