Pushing CZ gate performance via leakage reduction

Large-scale, transmon-based quantum processors based on CZ-gates are primarily dominated by two forms of errors: decoherence and leakage. These mechanisms trade off: shortening the gate reduces decoherence exposure but exacerbates fast-pulse–induced leakage, whereas lengthening it does the opposite.

Appropriate pulse shaping can suppress leakage, enabling shorter CZ gates and, in turn, lower error rates—both directly (less leakage) and indirectly (reduced decoherence due to shorter duration).

In this talk, we present a useful characterization and novel pulse-shaping methods for reducing leakage while improving gate performance using our transmon-based tunable coupler architecture [1]. We quantify our gate performance using leakage-aware randomized benchmarking and construct an error budget that attributes contributions to independently measured sources.

[1] E.A.Sete, et al. Phys. Rev. Applied 15, 064063 (2021)