Tunable Multi-qubit couplers with low residual ZZ interactions*

Maintaining high gate fidelities when scaling quantum processors to a large number of qubits is key to practically useful quantum computing.  Two-qubit gates based on tunable couplers now reach fidelities above 99.5% in superconducting qubit quantum processors, in which the qubits are typically arranged on a square grid with pair-wise qubit-qubit couplers. However, involving multi-qubit couplers that provide higher connectivity may lead to more efficient algorithms. In this work, we specifically discuss the challenges imposed by residual ZZ interactions in such multi-qubit tunable-coupler architectures. We analyze possibilities to suppress these off-resonant interactions by connecting qubits to the coupler with different polarities of the coupling. Moreover, we investigate the use of additional two-qubit couplers as a way to mitigate ZZ interactions.