Parametric-resonance entangling gates with a tunable coupler

TL;DR

This paper introduces a new parametric-resonance entangling gate method compatible with tunable couplers, achieving high-fidelity two-qubit gates without frequency collision issues, advancing scalable quantum computing.

Contribution

The authors develop a parametric-resonance gate activated by resonance conditions, compatible with tunable couplers, enabling high-fidelity, collision-free quantum gates.

Findings

Achieved 99.3% fidelity for iSWAP gate

Achieved 97.9% fidelity for CZ gate

Demonstrated compatibility with tunable coupler architectures

Abstract

High-fidelity parametric gates have been demonstrated with superconducting qubits via rf flux modulation of the qubit frequency. The modulation however leads to renormalization of the bare qubit-qubit coupling, thereby reducing the gate speed. Here, we realize a parametric-resonance gate, which is activated by bringing the average frequency of the modulated qubit in resonance with a static-frequency qubit while approximately retaining the bare qubit-qubit coupling. The activation of parametric-resonance gates does not depend on the frequency of modulation, allowing us to choose the modulation frequencies and avoid frequency collisions. Moreover, we show that this approach is compatible with tunable coupler architectures, which reduce always-on residual couplings. Using these techniques, we demonstrate iSWAP and CZ gates between two qubits coupled via a tunable coupler with average process fidelities as high as $99.3\%$ and $97.9\%$, respectively. The flexibility in activating parametric-resonance gates combined with a tunable coupler architecture provides a pathway for building large-scale quantum computers.