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Although two-qubit entangling gates are necessary for universal quantum computing, they are notoriously difficult to implement with high fidelity. Recently, tunable couplers have become a key component for realizing high-fidelity two-qubit…

Quantum Physics · Physics 2022-09-28 Hayato Goto

We present a native three-qubit entangling gate that exploits engineered interactions to realize control-control-target and control-target-target operations in a single coherent step. Unlike conventional decompositions into multiple…

Quantum Physics · Physics 2025-08-15 Xuexin Xu , Siyu Wang , Radhika Joshi , Rihan Hai , Mohammad H. Ansari

Scalable quantum information processing requires the ability to tune multi-qubit interactions. This makes the precise manipulation of quantum states particularly difficult for multi-qubit interactions because tunability unavoidably…

Superconducting quantum devices are a leading technology for quantum computation, but they suffer from several challenges. Gate errors, coherence errors and a lack of connectivity all contribute to low fidelity results. In particular,…

We demonstrate a robust quantum control framework that enables high-fidelity gate operations in semiconductor spin qubit systems with always-on couplings. Always-on interactions between qubits pose a fundamental challenge for quantum…

Quantum Physics · Physics 2025-03-18 Yong-Ju Hai , Shihang Zhang , Haoyu Guan , Peihao Huang , Yu He , Xiu-Hao Deng

Constructing a fault-tolerant quantum computer is a daunting task. Given any design, it is possible to determine the maximum error rate of each type of component that can be tolerated while still permitting arbitrarily large-scale quantum…

High-performance two-qubit gates have been reported with superconducting qubits coupled via a single-transmon coupler (STC). Most of them are implemented for qubits with a small detuning since reducing residual $ZZ$ coupling for highly…

Quantum Physics · Physics 2023-02-09 Kentaro Kubo , 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…

Implementing high-fidelity controlled two-qubit gates in dipole-dipole interacting systems, such as rare-earth-ion crystals, in hindered by spectral inhomogeneity and weak coupling. Existing method often rely on detuned pulses, making them…

Quantum Physics · Physics 2026-04-09 Licheng Lin , Jize Han , Peng Zhu , Ziyu Wang , Ying Yan , Jie Lu , Zhiguo Huang

Precise control of superconducting qubits is essential for advancing both quantum simulation and quantum error correction. Recently, transmon qubit systems employing the single-transmon coupler (STC) scheme have demonstrated high-fidelity…

Superconducting qubits provide a promising approach to large-scale fault-tolerant quantum computing. However, qubit connectivity on a planar surface is typically restricted to only a few neighboring qubits. Achieving longer-range and more…

Quantum dot hybrid qubits exploit an extended charge-noise sweet spot that suppresses dephasing and has enabled the experimental achievement of high-fidelity single-qubit gates. However, current proposals for two-qubit gates require tuning…

Quantum Physics · Physics 2020-01-28 Yuan-Chi Yang , S. N. Coppersmith , Mark Friesen

Parametric modulation, valued for its versatility, is widely employed in superconducting circuits for quantum simulations and high-fidelity two-qubit gates. Conventionally, the qubit coupling strength is determined by the amplitude of the…

Quantum Physics · Physics 2025-11-25 Zhuang Ma , Xianke Li , Hongyi Shi , Ruonan Guo , Jianwen Xu , Xinsheng Tan , Yang Yu

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

We analyze the experimental error budget of parametric resonance gates in a tunable coupler architecture. We identify and characterize various sources of errors, including incoherent, leakage, amplitude, and phase errors. By varying the…

Quantum Physics · Physics 2024-08-02 Eyob A. Sete , Vinay Tripathi , Joseph A. Valery , Daniel Lidar , Josh Y. Mutus

Superconducting qubits are a promising platform for building fault-tolerant quantum computers, with recent achievement showing the suppression of logical error with increasing code size. However, leakage into non-computational states, a…

The rapid growth in size of quantum devices demands efficient ways to control them, which is challenging for systems with thousands of qubits or more. Here, we present a simple yet powerful solution: robust, site-dependent control of an…

Quantum Physics · Physics 2023-12-15 Wenjie Gong , Soonwon Choi

In state-of-the-art superconducting quantum processors, each qubit is controlled by at least one control line that delivers control pulses generated at room temperature to qubits operating at millikelvin temperatures. While this strategy…

Quantum Physics · Physics 2024-03-21 Peng Zhao

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,…

The precise engineering of electromagnetic couplings is paramount for constructing scalable and highfidelity superconducting quantum processors. While essential for orchestrating qubit operations, these couplings also present significant…

Quantum Physics · Physics 2025-08-12 Ebrahim Forati , Brandon W. Langley , Ani Nersisyan , Reza Molavi