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arXiv · 2011.01261

Realization of high-fidelity CZ and ZZ-free iSWAP gates with a tunable coupler

Youngkyu Sung·Leon Ding·Jochen Braumüller·Antti Vepsäläinen·Bharath Kannan·Morten Kjaergaard·Ami Greene·Gabriel O. Samach·Chris McNally·David Kim·Alexander Melville·Bethany M. Niedzielski·Mollie E. Schwartz·Jonilyn L. Yoder·Terry P. Orlando·Simon Gustavsson·William D. Oliver
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Abstract

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 $99.76 \pm 0.07$% and $99.87 \pm 0.23$%, respectively, which are close to their $T_1$ limits.

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Youngkyu Sung, Leon Ding, Jochen Braumüller, Antti Vepsäläinen, Bharath Kannan, Morten Kjaergaard, Ami Greene, Gabriel O. Samach, Chris McNally, David Kim, Alexander Melville, Bethany M. Niedzielski, Mollie E. Schwartz, Jonilyn L. Yoder, Terry P. Orlando, Simon Gustavsson, William D. Oliver. 2020-11-02. Realization of high-fidelity CZ and ZZ-free iSWAP gates with a tunable coupler. https://doi.org/10.1103/physrevx.11.021058

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