Engineering multi-qubit interactions between superconducting flux qubits*

Nonpairwise multi-qubit interactions present a useful resource for quantum information processors. Their implementation would enable analog simulations of molecules and combinatorial optimization problems, and they could simplify error suppression and correction schemes. In this talk, we present a superconducting circuit architecture in which a coupling module mediates interactions between four flux qubits. The system Hamiltonian is estimated via multi-qubit pulse sequences that implement Ramsey-type interferometry between all neighboring excitation manifolds in the system. Interactions are determined with the coupler on and off, and we present evidence for multi-spin coupling mechanisms. Spectroscopic techniques, combined with numerical simulations of the circuit, permit an extrapolation of the interactions beyond the coherent regime of the qubits.