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Implementation of Conditional Phase Gates Based on Tunable Z Z Interactions

2020; American Physical Society; Volume: 125; Issue: 24 Linguagem: Inglês

10.1103/physrevlett.125.240502

1092-0145

Michele C. Collodo, J. Herrmann, Nathan Lacroix, Christian Kraglund Andersen, Ants Remm, Stefania Lazar, Jean-Claude Besse, T. Walter, Andreas Wallraff, Christopher Eichler,

Quantum Computing Algorithms and Architecture

High fidelity two-qubit gates exhibiting low cross talk are essential building blocks for gate-based quantum information processing. In superconducting circuits, two-qubit gates are typically based either on rf-controlled interactions or on the in situ tunability of qubit frequencies. Here, we present an alternative approach using a tunable cross-Kerr-type $ZZ$ interaction between two qubits, which we realize with a flux-tunable coupler element. We control the $ZZ$-coupling rate over 3 orders of magnitude to perform a rapid (38 ns), high-contrast, low leakage ($0.14\ifmmode\pm\else\textpm\fi{}0.24%$) conditional phase $CZ$ gate with a fidelity of $97.9\ifmmode\pm\else\textpm\fi{}0.7%$ as measured in interleaved randomized benchmarking without relying on the resonant interaction with a noncomputational state. Furthermore, by exploiting the direct nature of the $ZZ$ coupling, we easily access the entire conditional phase gate family by adjusting only a single control parameter.