Building and benchmarking diabatic entangling gates for frequency-tunable qubits, part I

One of the key needs in quantum computing are gates that are fast and precise, requiring minimization of the control errors and the suppression of leakage out of the computational states. We present a non-adiabatic protocol for iSWAP-like gates with minimal leakage and duration close to the speed limit. The key notion behind our approach is minimizing the gate error by synchronizing the Rabi clocks in the one- and two-excitation channels in a pair of transmon qubits to align minima of the leakage and residual swap population. This, in turn, can be accomplished by utilizing limited but sufficient tunability of the “fixed” interqubit coupling via a proper choice of the three key parameters such as interaction frequency, hold time and overshoot between the qubit frequencies near the avoided crossing. We show that our approach can be extended to other gate operations and discuss pulse-shape optimization suitable for particular gates and architectures.