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Entangling gates between neighboring physical qubits are essential for quantum error correction. Implementing them in an all-microwave manner simplifies signal routing and control apparatus of superconducting quantum processors. We propose…

Quantum Physics · Physics 2025-11-11 Shotaro Shirai , Shinichi Inoue , Shuhei Tamate , Rui Li , Yasunobu Nakamura , Atsushi Noguchi

The transmon, a fabrication-friendly superconducting qubit, remains a leading candidate for scalable quantum computing. Recent advances in tunable couplers have accelerated progress toward high-performance quantum processors. However,…

The superconducting transmon qubit is currently a leading qubit modality for quantum computing, but gate performance in quantum processor with transmons is often insufficient to support running complex algorithms for practical applications.…

Quantum Physics · Physics 2024-09-12 Peng Zhao , Dong Lan , Peng Xu , Guangming Xue , Mace Blank , Xinsheng Tan , Haifeng Yu , Yang Yu

Dynamical decoupling is effective in reducing gate errors in most quantum computation platforms and is therefore projected to play an essential role in future fault-tolerant constructions. In superconducting circuits, however, it has proven…

Quantum Physics · Physics 2024-03-15 Ido Zuk , Daniel Cohen , Alexey V. Gorshkov , Alex Retzker

Striving for higher gate fidelity is crucial not only for enhancing existing noisy intermediate-scale quantum (NISQ) devices but also for unleashing the potential of fault-tolerant quantum computation through quantum error correction. A…

Quantum Physics · Physics 2024-11-27 Rui Li , Kentaro Kubo , Yinghao Ho , Zhiguang Yan , Yasunobu Nakamura , Hayato Goto

High-fidelity two-qubit gates are essential for scalable quantum computing. We present a scheme based on superconducting transmon qubits and a control pulse delivery protocol that enables arbitrary controlled-phase gates modulated solely by…

Tunable couplers enable high-fidelity two-qubit gates leveraging high on/off coupling ratios and reduced crosstalk within a single design. We investigate a galvanically connected direct-current superconducting quantum interference device…

Novel qubits with intrinsic noise protection constitute a promising route for improving the coherence of quantum information in superconducting circuits. However, many protected superconducting qubits exhibit relatively low transition…

Quantum Physics · Physics 2022-12-05 Andrea Maiani , Morten Kjaergaard , Constantin Schrade

Tunable couplers in superconducting quantum computers have enabled fast and accurate two-qubit gates, with reported high fidelities over 99% in various architectures and gate implementation schemes. However, there are few tunable couplers…

Quantum Physics · Physics 2024-08-23 Kentaro Kubo , Yinghao Ho , Hayato Goto

Scaling superconducting quantum processors beyond the constraints of monolithic planar architectures is essential for fault-tolerant quantum computation. Here we demonstrate a three-dimensional (3D) integrated superconducting quantum…

Increasing connectivity and decreasing qubit-state delocalization without compromising the speed and accuracy of elementary gate operations are topical challenges in the development of large-scale superconducting quantum computers. In this…

Quantum Physics · Physics 2026-03-12 Tuure Orell , Hao Hsu , Joona Andersson , Jani Tuorila , Frank Deppe , Hsiang-Sheng Ku

Superconducting fluxonium qubits provide a promising alternative to transmons on the path toward large-scale superconductor-based quantum computing due to their better coherence and larger anharmonicity. A major challenge for multi-qubit…

Mitigating crosstalk errors, whether classical or quantum mechanical, is critically important for achieving high-fidelity entangling gates in multi-qubit circuits. For weakly anharmonic superconducting qubits, unwanted $ZZ$ interactions can…

Superconducting qubits have achieved remarkable progress in gate fidelity and coherence, yet their typical nearest-neighbor connectivity presents constraints for implementing complex quantum circuits. Here, we introduce a cavity-mediated…

Quantum Physics · Physics 2026-02-10 Shinyoung Hwang , Sangyeon Lee , Eunjong Kim

Superconducting qubits have achieved exceptional gate fidelities, exceeding the error-correction threshold in recent years. One key ingredient of such improvement is the introduction of tunable couplers to control the qubit-to-qubit…

To reduce circuit depth when executing Quantum algorithms, it is necessary to maximize qubit connectivity on a near-term quantum processor. While addressing this, we also need to ensure high gate fidelity, suppression of unwanted ZZ…

Quantum Physics · Physics 2026-02-09 Uday Sannigrahi , Amlan Chakrabarti , Swapnil Saha , Shrinjita Biswas

All-microwave control of fixed-frequency superconducting quantum systems offers the potential to reduce control circuit complexity and increase system coherence. Nevertheless, due to the limited control flexibility in qubit parameters, one…

Quantum Physics · Physics 2024-10-11 Ling Jiang , Peng Xu , Shengjun Wu , Jian-An Sun , Fu-Quan Dou

Superconducting qubits are among the most promising candidates for building quantum computers. Despite significant improvements in qubit coherence, achieving a fault-tolerant quantum computer remains a major challenge, largely due to…

Quantum Physics · Physics 2024-07-12 Xuexin Xu

A high-fidelity CZ gate utilizing a double-transmon coupler (DTC) has recently been demonstrated as a building block for superconducting quantum processors. Like many other kinds of tunable couplers, however, the DTC requires a finite DC…

Quantum Physics · Physics 2025-07-30 Rui Li , Kentaro Kubo , Yinghao Ho , Zhiguang Yan , Shinichi Inoue , Yasunobu Nakamura , Hayato Goto

Superconducting quantum processors have largely converged on transmon-based architectures, while alternative qubit modalities with intrinsic error protection have lacked a demonstrated path to scalable system integration. In particular,…