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Versatile parametric coupling between two statically decoupled transmon qubits



Xiaoyue Jin, Zachary Parrott, SHLOMI KOTLER, Katarina Cicak, Florent Lecocq, John Teufel, Joe Aumentado, Raymond Simmonds


Parametric coupling is a powerful technique for generating tunable interactions between superconducting circuits using only microwave tones. Here, we present a highly flexible parametric coupling scheme demonstrated with two transmon qubits, which can be employed for multiple purposes, including the removal of residual $ZZ$ coupling and the implementation of driven swap or swap-free controlled-$Z$ (c$Z$) gates. Our fully integrated coupler design is only weakly flux tunable, mostly cancels static linear coupling between the qubits, avoids internal coupler dynamics or excitations, and operates with rf-pulses. We show that residual $ZZ$ coupling can be reduced with a parametric dispersive tone down to an experimental uncertainty of 5.5kHz. Additionally, randomized benchmarking over more than 12 hours reveals that the parametric swap c$Z$ gate achieves an average fidelity of 99.4\% in a gate duration of 60ns, while the dispersive parametric swap-free c$Z$ gate attains a fidelity of 99.5\% in only 30ns, while over shorter timescales, fidelity peaks at about 99.7\%. We believe this is the fastest and highest fidelity gate achieved with on-chip parametric coupling to date. We further explore the dependence of gate fidelity on gate duration for both p-swap and p-swap-free c$Z$ gates, providing insights into the possible error sources for these gates. Overall, our findings demonstrate a versatility, precision, speed, and high performance not seen in previous parametric approaches. Finally, our design opens up new possibilities for creating larger, modular systems of superconducting qubits.
Nature Physics


Quantum Computing, Qubit, Transmon, Parametric Coupling, Quantum Gates, Gate Fidelity


Jin, X. , Parrott, Z. , KOTLER, S. , Cicak, K. , Lecocq, F. , Teufel, J. , Aumentado, J. and Simmonds, R. (2023), Versatile parametric coupling between two statically decoupled transmon qubits, Nature Physics (Accessed July 12, 2024)


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Created May 4, 2023, Updated June 18, 2024