Efficient Multi-Qubit Hamiltonian Characterization and Retuning

Accurately characterizing Hamiltonian interaction strengths across a network of interconnected qubits is essential for calibration and quantum simulation. As qubit counts grow, serial approaches to spectroscopy and calibration become inefficient, motivating parallelization of traditional one- and two-qubit quantum characterization, verification, and validation (QCVV) methods. We present a scalable protocol in which all qubits perform synchronized, modified Ramsey experiments to extract all one- and two-body Z-type interactions across a hardware graph of arbitrary connectivity. The number of required experiments scales linearly with the chromatic number of the square of the hardware graph. Using this protocol, we experimentally extract interaction terms and show that one-body terms can be reprogrammed via qubit drive frequency shifts. These results enable targeted rescaling or cancellation of Hamiltonian terms to improve gate fidelities and inform more accurate, low-latency updates to simulation models.