Distinguishing Multispin Interactions from Lower-Order Effects

Multispin interactions can be engineered with artificial quantum spins. However, it is challenging to verify such interactions experimentally. Here, we describe two methods to characterize the n-local cou-pling of n spins. First, we analyze the variation of the transition energy of the static system as a function of local spin fields. Standard measurement techniques are employed to distinguish n-local interactions between up to five spins from lower-order contributions in the presence of noise and spurious fields and couplings. Second, we show a detection technique that relies on time-dependent driving of the coupling term. Generalizations to larger system sizes are analyzed for both static and dynamic detection methods and we find that the dynamic method is asymptotically optimal when increasing the system size. The pro-posed methods enable robust exploration of multispin interactions across a broad range of both coupling strengths and qubit modalities.