Precise Hamiltonian identification of a superconducting quantum processor (part 2)

The required precision to perform quantum simulations beyond the capabilities of classical computers imposes major experimental and theoretical challenges. Implementing a novel algorithm, we infer all parameters of the bosonic Hamiltonian that governs the dynamics of excitations in a two-dimensional grid of nearest-neighbour coupled superconducting qubits. For five and six coupled qubits, we identify Hamiltonian parameters with sub-MHz precision and construct a spatial implementation error map for a grid of 27 qubits. Our results quantify the implementation accuracy of analog dynamics and introduce a diagnostic toolkit for understanding, calibrating, and improving analog quantum processors.