A double-resonator coupler for high-fidelity two-qubit gates between superconducting qubits

Tunable Coupler is a classical hardware coupling approach for quantum computing hardware. Source: latex text.

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 in the absence of direct qubit-qubit coupling, 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.

Key Findings

Links

• arXiv: 2609.05222

Verification Report

Verification status: verified. Disputes resolved: 0. Citation count snapshot (Semantic Scholar): 0. Ingestion source: latex. Text truncated: no.