Cross-Cross Resonance Gate

Abstract

The implementation of high-fidelity swapping operations is of vital importance for executing quantum algorithms on a quantum processor with limited connectivity. We present an efficient pulse-control technique, the cross-cross resonance (CCR) gate, to implement iswap and swap gates with dispersively coupled fixed-frequency transmon qubits. The key to the operation of the CCR gate is the simultaneous driving of both of the coupled qubits at the frequency of another qubit, whereby a fast two-qubit interaction roughly equivalent to ZX+XZ entangling gates is realized without strongly driving the qubits. We develop a calibration technique for the CCR gate and evaluate the performance of the iswap and swap gates. The CCR gate shows remarkable improvements in the average gate error from the conventional decomposition based on the cross-resonance gate.