Impact of tunable couplers on parity-check performance in superconducting quantum processors for error correction

Among many requirements, quantum error correction necessitates accurate control of the interactions between qubits. In the field of superconducting qubits, this has motivated the development of tunable-coupling schemes. We implement a tunable-coupling architecture and analyze the impact of the coupler bias on gate and readout performance in a multi-qubit setting. We detail the implementation of controlled-Z gates with fidelity exceeding 99% and evidence their benefits through weight-2 parity checks achieving defect rates below 10% over 100 repetitions, without applying any leakage reduction method. Finally, we study the impact of coupled spectator qubits on parity-check performance as a function of coupling strength.