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High-quality two-qubit gate operations are crucial for scalable quantum information processing. Often, the gate fidelity is compromised when the system becomes more integrated. Therefore, a low-error-rate, easy-to-scale two-qubit gate…

Quantum Physics · Physics 2020-12-24 Yuan Xu , Ji Chu , Jiahao Yuan , Jiawei Qiu , Yuxuan Zhou , Libo Zhang , Xinsheng Tan , Yang Yu , Song Liu , Jian Li , Fei Yan , Dapeng Yu

Improving two-qubit gate performance and suppressing crosstalk are major, but often competing, challenges to achieving scalable quantum computation. In particular, increasing the coupling to realize faster gates has been intrinsically…

Quantum Physics · Physics 2021-09-29 A. Kandala , K. X. Wei , S. Srinivasan , E. Magesan , S. Carnevale , G. A. Keefe , D. Klaus , O. Dial , D. C. McKay

Currently available quantum computing hardware based on superconducting transmon architectures realizes networks of hundreds of qubits with the possibility of controlled nearest-neighbor interactions. However, the inherent noise and…

Quantum Physics · Physics 2023-11-07 Andreas Ketterer , Thomas Wellens

Cross-talk between qubits is one of the main challenges for scaling superconducting quantum processors. Here, we use the density-matrix renormalization-group to numerically analyze lattices of superconducting qubits from a perspective of…

Quantum Physics · Physics 2025-12-08 F. Lange , L. Heunisch , H. Fehske , D. P. DiVincenzo , M. J. Hartmann

We introduce a novel superconducting qubit architecture utilizing parallel arrays of Josephson junctions. This design offers a substantialy improved relative anharmonicity, typically within the range of $|\alpha_r| \approx 0.1 - 0.3$, while…

Quantum Physics · Physics 2024-04-09 Oguzhan Can , Marcel Franz

Implementation of high-fidelity gate operations on integrated-qubit systems is of vital importance for fault-tolerant quantum computation. Qubit frequency allocation is an essential part of improving control fidelity. A metric for qubit…

Quantum Physics · Physics 2025-10-24 Kentaro Heya , Moein Malekakhlagh , Seth Merkel , Naoki Kanazawa , Emily Pritchett

We demonstrate fast two-qubit gates using a parity-violated superconducting qubit consisting of a capacitively-shunted asymmetric Josephson-junction loop under a finite magnetic flux bias. The second-order nonlinearity manifesting in the…

In superconducting qubits, the interaction of the qubit degree of freedom with quasiparticles defines a fundamental limitation for the qubit coherence. We develop a theory of the pure dephasing rate \Gamma_{\phi} caused by quasiparticles…

Mesoscale and Nanoscale Physics · Physics 2012-11-22 G. Catelani , Simon E. Nigg , S. M. Girvin , R. J. Schoelkopf , L. I. Glazman

Tunable Josephson harmonics open new avenues for qubit design. We demonstrate a superconducting circuit element consisting of a tunnel junction in series with a SQUID loop, yielding a Josephson potential whose harmonic content is strongly…

Scaling superconducting quantum processors is fundamentally limited by the escalating complexity of cryogenic wiring and the debilitating effects of microwave crosstalk and Purcell decay. This paper proposes the concept of…

Quantum Physics · Physics 2025-12-22 Sajjad Taravati

Accurate and efficient implementation of parallel quantum gates is crucial for scalable quantum information processing. However, the unavoidable crosstalk between qubits in current noisy processors impedes the achievement of high gate…

Quantum Physics · Physics 2026-01-06 Xiaodong Yang , Ran Liu , Jun Li

Niobium offers the benefit of increased operating temperatures and frequencies for Josephson junctions, which are the core component of superconducting devices. However existing niobium processes are limited by more complicated fabrication…

Quantum Physics · Physics 2024-02-23 Alexander Anferov , Kan-Heng Lee , Fang Zhao , Jonathan Simon , David I. Schuster

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…

Superconductor qubits typically use aluminum-aluminum oxide tunnel junctions to provide the non-linear inductance. Junctions with semiconductor barriers make it possible to vary the superconductor material and explore beyond aluminum. We…

Quantum optimal control theory allows to design accurate quantum gates. We employ it to design high-fidelity two-bit gates for Josephson charge qubits in the presence of both leakage and noise. Our protocol considerably increases the…

Quantum Physics · Physics 2009-11-13 Simone Montangero , Tommaso Calarco , Rosario Fazio

In this paper we discuss solid-state nanoelectronic realizations of Josephson flux qubits with large tunneling amplitude between the two macroscopic states. The latter can be controlled via the height and wells form of the potential…

Superconductivity · Physics 2013-04-02 V. I. Shnyrkov , A. A. Soroka , S. I. Melnik

Two qubit gates constitute fundamental building blocks in the realization of large-scale quantum devices. Using superconducting circuits, two-qubit gates have previously been implemented in different ways with each method aiming to maximize…

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

Quantum processing units (QPUs) based on superconducting Josephson junctions promise significant advances in quantum computing. However, they face critical challenges. Decoherence, scalability limitations, and error correction overhead…

Superconductivity · Physics 2025-04-04 Omid Mohebi , Alireza Hesam Mohseni

With the long coherence time, the fixed-frequency transmon qubit is a promising qubit modality for quantum computing. Currently, diverse qubit architectures that utilize fixed-frequency transmon qubits have been demonstrated with…

Quantum Physics · Physics 2022-06-29 Peng Zhao , Teng Ma , Yirong Jin , Haifeng Yu