  Native multi-qubit parity gates have various potential quantum computing
applications, such as entanglement creation, logical state encoding and parity
measurement in quantum error correction. Here, using simultaneous
cross-resonance drives on two control qubits with a common target, we
demonstrate an efficient implementation of a three-qubit parity gate. We have
developed a calibration procedure based on the one for the echoed
cross-resonance gate. We confirm that our use of simultaneous drives leads to
higher interleaved randomized benchmarking fidelities than a naive
implementation with two consecutive CNOT gates. We also demonstrate that our
simultaneous parity gates can significantly improve the parity measurement
error probability for the heavy-hexagon code on an IBM Quantum processor using
seven superconducting qubits with all-microwave control.
