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Superconducting fluxonium qubits show a highly tunable energy-level structure, with transition frequencies spanning from a few MHz to few GHz. This range is well-aligned to the operational frequencies of highly coherent micro- and…

Quantum Physics · Physics 2025-08-26 Roson Nongthombam , Anshika Ranjan , Amarendra K. Sarma , Vibhor Singh

We introduce a new hybrid qubit consisting of a Majorana qubit interacting with a transmon longitudinally coupled to a resonator. To do so, we equip the longitudinal transmon qubit with topological quasiparticles, supported by an array of…

Quantum Physics · Physics 2020-09-28 Alec Dinerstein , Caroline S. Gorham , Eugene F. Dumitrescu

We describe the design for a scalable, solid-state quantum-information-processing architecture based on the integration of GHz-frequency nanomechanical resonators with Josephson tunnel junctions, which has the potential for demonstrating a…

Quantum Physics · Physics 2009-11-10 Michael R. Geller , Andrew N. Cleland

With the increasing size of quantum processors, sub-modules that constitute the processor hardware will become too large to accurately simulate on a classical computer. Therefore, one would soon have to fabricate and test each new design…

Different nanofabricated superconducting circuits based on Josephson junctions have already achieved a degree of quantum coherence sufficient to demonstrate coherent superpositions of their quantum states. These circuits are considered for…

Superconductivity · Physics 2009-11-10 E. Collin , G. Ithier , A. Aassime , P. Joyez , D. Vion , D. Esteve

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…

Building more powerful quantum computers requires manufacturing processes with tight tolerances. To improve the tolerances on Josephson junctions, techniques to fine tune their properties after fabrication have been developed. Understanding…

Quantum Physics · Physics 2025-11-17 Oscar W. Kennedy , Jared H. Cole , Connor D. Shelly

The protection of superconducting qubits from certain noise sources often comes at the cost of increased sensitivity to other decoherence channels. Here, we explore a route to avoid this tradeoff by encoding quantum information in quantum…

We report superconducting fluxonium qubits with coherence times largely limited by energy relaxation and reproducibly satisfying T2 > 100 microseconds (T2 > 300 microseconds in one device). Moreover, given the state of the art values of the…

We present a framework that combines the adjoint-state method together with reverse-time backpropagation to solve prohibitively large open-system quantum control problems. Our approach enables the optimization of arbitrary cost functions…

Quantum Physics · Physics 2025-02-21 Ronan Gautier , Élie Genois , Alexandre Blais

Quantum transducers are critical for quantum interconnect, enabling coherent signal transfer across disparate frequency domains. Beyond material and device advances, protocol design has become a powerful means to improve transduction. We…

Quantum Physics · Physics 2026-03-05 Pengcheng Liao , Haowei Shi , Quntao Zhuang

Tunneling defects in disordered materials form spurious two-level systems which are a major source of decoherence for micro-fabricated quantum devices. For superconducting qubits, defects in tunnel barriers of submicrometer-sized Josephson…

Quantum Physics · Physics 2022-03-09 Alexander Bilmes , Serhii Volosheniuk , Alexey V. Ustinov , Jürgen Lisenfeld

We analyze the quantum information processing capability of a superconducting transmon circuit used to mediate interactions between quantum information stored in a collection of phononic crystal cavity resonators. Having only a single…

Quantum Physics · Physics 2019-07-31 Marek Pechal , Patricio Arrangoiz-Arriola , Amir H. Safavi-Naeini

We consider a superconducting half-wavelength resonator that is grounded at its both ends and contains a single Josephson junction. Previously this circuit was considered as a unimon qubit in the single-mode approximation where…

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…

We study a recently demonstrated design for a high-performance tunable coupler suitable for superconducting Xmon and planar transmon qubits [Y. Chen et al., arXiv:1402.7367]. The coupler circuit uses a single flux-biased Josephson junction…

Quantum Physics · Physics 2015-09-17 Michael R. Geller , Emmanuel Donate , Yu Chen , Charles Neill , Pedram Roushan , John M. Martinis

Josephson junctions made from aluminium and its oxide are the most commonly used functional elements for superconducting circuits and qubits. It is generally known that the disordered thin-film AlOx contains atomic tunneling systems.…

Superconductivity · Physics 2018-05-30 Saskia M. Meißner , Arnold Seiler , Jürgen Lisenfeld , Alexey V. Ustinov , Georg Weiss

Superconducting quantum circuits are a promising hardware platform for realizing a fault-tolerant quantum computer. Accelerating progress in this field of research demands general approaches and computational tools to analyze and design…

Quantum Physics · Physics 2023-09-27 Taha Rajabzadeh , Zhaoyou Wang , Nathan Lee , Takuma Makihara , Yudan Guo , Amir H. Safavi-Naeini

Like a quantum computer designed for a particular class of problems, a quantum simulator enables quantitative modeling of quantum systems that is computationally intractable with a classical computer. Quantum simulations of quantum…

Quantum Physics · Physics 2013-07-16 William E. Shanks , Devin L. Underwood , Andrew A. Houck

Van-der-Waals (vdW) assembly enables the fabrication of novel Josephson junctions utilizing an atomically sharp interface between two exfoliated and relatively twisted $\rm{Bi_2Sr_2CaCu_2O_{8+x}}$ (Bi2212) flakes. In a range of twist angles…

Superconductivity · Physics 2023-08-10 Valentina Brosco , Giuseppe Serpico , Valerii Vinokur , Nicola Poccia , Uri Vool