Vlatko Vedral

Approximation based on perturbation theory is the foundation for most of the quantitative predictions of quantum mechanics, whether in quantum many-body physics, chemistry, or other domains. Quantum computing provides an alternative to the perturbation paradigm, yet current quantum processors with few noisy qubits are of limited practical utility. In this talk, we introduce perturbative quantum simulation, which combines the complementary strengths of the two approaches, enabling the solution of large quantum problems using limited intermediate-scale quantum hardware. The use of a quantum processor alleviates the need to identify a solvable unperturbed Hamiltonian, while the introduction of perturbative coupling permits a quantum processor to simulate systems with larger sizes. We present an explicit perturbative expansion that mimics the Dyson series expansion and involves only local unitary operations. We then discuss its optimality over other expansions under certain conditions. This perturbative approach is benchmarked by simulating the interacting dynamics of representative quantum systems.