Error suppression in the cross-resonance gate via recursive DRAG.*

The cross-resonance gate is one of the widely used two-qubit gates for superconducting qubits. The state-of-the-art experiments have demonstrated high-fidelity gate operations and it is also the default two-qubit gate on the IBM NISQ devices. The cross-resonance gate is known to be subjected to several coherent errors such as non-adiabatic transitions on the control qubit and ZZ phase error. They are often suppressed through long pulse ramping time and echoed gate design, which inevitably increases the gate time.

In this talk, we present a systematic way to suppress all these coherent errors through the recursive DRAG method. In particular, we derive analytical expressions for improved cross-resonance pulses, with which, all the three dominant non-adiabatic transitions on the control qubit can be suppressed to their leading order. In addition, we show how the remaining phase errors such as dynamical ZZ and ZY errors can be compensated by a DRAG-like pulse on the target qubit and detuning of the CR drive. We numerically test the performance and show the improvement in a large range of parameters in the straddling regime. The method can also be applied to echoed cross-resonance gates or other quantum operations, where multiple coherent errors are present in the dynamics.