Fig. 1: Microwave-activated cross-Kerr entanglement.
From: High-fidelity qutrit entangling gates for superconducting circuits
Two transmon qutrits with qubit frequency ωi, anharmonicity ηi, and coupling J, experience a dynamical cross-Kerr (ZZ-like) entanglement when simultaneously driven by an off-resonant microwave drive. The strength of the cross-Kerr entangling terms (α11, α12, α21, α22) is tuned by the parameters of the microwave drive (ωd, Ω, ϕ).
