A double-resonator coupler for high-fidelity two-qubit gates between superconducting qubits
Year: 2026
Type: preprint
Abstract: Tunable couplers have enabled two-qubit gate fidelities in superconducting quantum processors to approach $99.9\%$, yet simultaneously suppressing residual interactions and maintaining flexible qubit-frequency allocation remain central challenges for scaling. Here, we propose a double-resonator coupler (DRC) consisting of two resonators interconnected by a single Josephson junction and a capacitor. The hybridized resonator modes provide two mediated exchange paths whose interference controls the qubit-qubit interaction. The DRC enables complete cancellation of residual $ZZ$ interaction for qubit-qubit detunings well outside the straddling regime, even without direct inter-qubit capacitance, thereby relaxing constraints on frequency allocation and qubit placement. Away from the idle point, the same circuit provides a strong $ZZ$ interaction of approximately $70\,\mathrm{MHz}$, enabling a $20\,\mathrm{ns}$ controlled-Z gate with simulated coherent infidelity below $10^{-5}$. These results establish the DRC as a flexible single-junction coupler architecture for high-fidelity superconducting quantum processors.
Source: arXiv (Cornell University)
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G45824782, G6390571125, G754601064
OpenAlex ID: W7211899689