Curator's Take
AI Commentary
This article introduces a double‑resonator coupler that uses interference between two mediated exchange paths to null out unwanted ZZ crosstalk even when qubits are far detuned, removing a long‑standing bottleneck in frequency allocation for large superconducting arrays. By delivering a strong, tunable ZZ interaction of about 70 MHz the same device can execute a 20 ns controlled‑Z gate with simulated coherent errors below 10⁻⁵, pushing two‑qubit fidelities toward the 99.999% regime. The approach offers a single‑junction, compact hardware solution that could simplify processor layout and accelerate scaling of high‑performance quantum computers.
— Mark Eatherly
Summary
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.