2020/11/30 by Youngkyu Sung, Leon Ding, Jochen Braumüller +14 · 3 citations
Physics and Astronomy · #quant-ph
paper · pdf · doi:10.1103/physrevx.11.021058
published as Phys. Rev. X 11, 021058 (2021) · 34 pages, 39 figures
arxiv created 2021/06/17 · arxiv updated 2021/06/18
High-fidelity two-qubit gates at scale are a key requirement to realize the full promise of quantum computation and simulation. The advent and use of coupler elements to tunably control two-qubit interactions has improved operational fidelity in many-qubit systems by reducing parasitic coupling and frequency crowding issues. Nonetheless, two-qubit gate errors still limit the capability of near-term quantum applications. The reason, in part, is the existing framework for tunable couplers based on the dispersive approximation does not fully incorporate three-body multi-level dynamics, which is essential for addressing coherent leakage to the coupler and parasitic longitudinal (ZZ) interactions during two-qubit gates. Here, we present a systematic approach that goes beyond the dispersive approximation to exploit the engineered level structure of the coupler and optimize its control. Using this approach, we experimentally demonstrate CZ and ZZ-free iSWAP gates with two-qubit interaction fidelities of 99.76 ± 0.07% and 99.87 ± 0.23%, respectively, which are close to their T1 limits.