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As the superconducting qubit platform matures towards ever-larger scales in the race towards a practical quantum computer, limitations due to qubit inhomogeneity through lack of process control become apparent. To benefit from the advanced…

Superconducting quantum circuits provide a versatile platform for studying quantum materials by leveraging precise microwave control and utilizing the tools of circuit quantum electrodynamics (QED). Hybrid circuit devices incorporating…

Mesoscale and Nanoscale Physics · Physics 2025-06-24 Sheng-Wen Huang , Ramya Suresh , Jian Liao , Botao Du , Zachary Miles , Leonid P. Rokhinson , Yong P. Chen , Ruichao Ma

The Superconducting Quasiparticle-Amplifying Transmon (SQUAT) is a new sensor architecture for THz (meV) detection based on a weakly charge-sensitive transmon directly coupled to a transmission line. In such devices, energy depositions…

The performance of various superconducting devices operating at ultra-low temperatures is impaired by the presence of non-equilibrium quasiparticles. Inelastic quasiparticle (QP) tunneling across Josephson junctions in superconducting…

Quantum Physics · Physics 2024-05-14 Plamen Kamenov , Thomas DiNapoli , Michael Gershenson , Srivatsan Chakram

Significant progress has been made in building large-scale superconducting quantum processors based on flip-chip technology. In this work, we use the flip-chip technology to realize a modified transmon qubit, donated as the "flipmon", whose…

Coherent operation of gate-voltage-controlled hybrid transmon qubits (gatemons) based on semiconductor nanowires was recently demonstrated. Here we experimentally investigate the anharmonicity in epitaxial InAs-Al Josephson junctions, a key…

Mesoscale and Nanoscale Physics · Physics 2018-02-28 A. Kringhøj , L. Casparis , M. Hell , T. W. Larsen , F. Kuemmeth , M. Leijnse , K. Flensberg , P. Krogstrup , J. Nygård , K. D. Petersson , C. M. Marcus

Superconducting qubits are among the most promising platforms for realizing practical quantum computers. One requirement to create a quantum processor is nonlinearity, which in superconducting circuits is typically achieved by sandwiching a…

We demonstrate strong suppression of charge dispersion in a semiconductor-based transmon qubit across Josephson resonances associated with a quantum dot in the junction. On resonance, dispersion is drastically reduced compared to…

Mesoscale and Nanoscale Physics · Physics 2020-06-23 A. Kringhøj , B. van Heck , T. W. Larsen , O. Erlandsson , D. Sabonis , P. Krogstrup , L. Casparis , K. D. Petersson , C. M. Marcus

Superconducting integrated circuits have demonstrated a tremendous potential to realize integrated quantum computing processors. However, the downside of the solid-state approach is that superconducting qubits suffer strongly from energy…

As low-loss non-linear elements, Josephson junctions are the building blocks of superconducting qubits. The interaction of the qubit degree of freedom with the quasiparticles tunneling through the junction represent an intrinsic relaxation…

Mesoscale and Nanoscale Physics · Physics 2011-08-25 G. Catelani , R. J. Schoelkopf , M. H. Devoret , L. I. Glazman

We review the main theoretical and experimental results for the transmon, a superconducting charge qubit derived from the Cooper pair box. The increased ratio of the Josephson to charging energy results in an exponential suppression of the…

Mesoscale and Nanoscale Physics · Physics 2009-08-11 A. A. Houck , Jens Koch , M. H. Devoret , S. M. Girvin , R. J. Schoelkopf

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

Magnetic-field-resilient superconducting circuits enable sensing applications and hybrid quantum-computing architectures involving spin or topological qubits and electro-mechanical elements, as well as studying flux noise and quasiparticle…

Quantum Physics · Physics 2022-03-15 J. Krause , C. Dickel , E. Vaal , M. Vielmetter , J. Feng , R. Bounds , G. Catelani , J. M. Fink , Yoichi Ando

The quasicharge superconducting qubit realizes the dual of the transmon and shows strong robustness to flux and charge fluctuations thanks to a very large inductance closed on a Josephson junction. At the same time, a weak anharmonicity of…

Mesoscale and Nanoscale Physics · Physics 2023-12-06 Luca Chirolli , Matteo Carrega , Francesco Giazotto

Short dephasing times pose one of the main challenges in realizing a quantum computer. Different approaches have been devised to cure this problem for superconducting qubits, a prime example being the operation of such devices at optimal…

Mesoscale and Nanoscale Physics · Physics 2007-10-14 Jens Koch , Terri M. Yu , Jay Gambetta , A. A. Houck , D. I. Schuster , J. Majer , Alexandre Blais , M. H. Devoret , S. M. Girvin , R. J. Schoelkopf

The coherent tunnelling of Cooper pairs across Josephson junctions (JJs) generates a nonlinear inductance that is used extensively in quantum information processors based on superconducting circuits, from setting qubit transition…

The continuous miniaturisation of metal-oxide-semiconductor field-effect transistors (MOSFETs) from long- to short-channel architectures has advanced beyond the predictions of Moore's Law. Continued advances in semiconductor electronics,…

Systems and Control · Electrical Eng. & Systems 2025-10-30 Yusheng Xiong , Kaveh Delfanazari

We introduce a hybrid qubit based on a semiconductor nanowire with an epitaxially grown superconductor layer. Josephson energy of the transmon-like device ("gatemon") is controlled by an electrostatic gate that depletes carriers in a…

Mesoscale and Nanoscale Physics · Physics 2015-09-22 T. W. Larsen , K. D. Petersson , F. Kuemmeth , T. S. Jespersen , P. Krogstrup , J. Nygard , C. M. Marcus

Circuit quantum electrodynamics systems are typically built from resonators and two-level artificial atoms, but the use of multi-level artificial atoms instead can enable promising applications in quantum technology. Here we present an…

Quantum Physics · Physics 2015-08-05 É. Dumur , B. Küng , A. K. Feofanov , T. Weissl , N. Roch , C. Naud , W. Guichard , O. Buisson

The anharmonicity of a transmon qubit, defined as the difference in energy level spacing, is a key design parameter. In transmons built from hybrid superconductor-semiconductor Josephson elements, the anharmonicity is tunable with gate…