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We study the realization of a Toffoli gate with superconducting qubits in a circuit-QED setup using quantum-control methods. Starting with optimized piecewise-constant control fields acting on all qubits and typical strengths of XY-type…

Quantum Physics · Physics 2012-02-14 Vladimir M. Stojanovic , A. Fedorov , A. Wallraff , C. Bruder

Quantum algorithms on near-term quantum processors are typically executed using shallow quantum circuits composed of one- and two-qubit gates. However, as circuit depth and gate number increase, gate imperfections and qubit decoherence…

Geometric phases are noise-resilient, and thus provide a robust way towards high fidelity quantum manipulation. Here we experimentally demonstrate arbitrary non-adiabatic holonomic single-qubit quantum gates for both a superconducting…

Quantum Physics · Physics 2018-09-14 Y. Xu , W. Cai , Y. Ma , X. Mu , L. Hu , Tao Chen , H. Wang , Y. P. Song , Zheng-Yuan Xue , Zhang-qi Yin , L. Sun

Semiconductor double quantum dot hybrid qubits are promising candidates for high-fidelity quantum computing. However, their performance is limited by charge noise, which is ubiquitous in solid-state devices, and phonon-induced dephasing.…

Mesoscale and Nanoscale Physics · Physics 2019-09-04 Yuan-Chi Yang , S. N. Coppersmith , Mark Friesen

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

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

Physical implementations of qubits can be extremely sensitive to environmental coupling, which can result in decoherence. While efforts are made for protection, coupling to the environment is necessary to measure and manipulate the state of…

Assembling future large-scale quantum computers out of smaller, specialized modules promises to simplify a number of formidable science and engineering challenges. One of the primary challenges in developing a modular architecture is in…

Engineering high-fidelity two-qubit gates is an indispensable step toward practical quantum computing. For superconducting quantum platforms, one important setback is the stray interaction between qubits, which causes significant coherent…

Quantum Physics · Physics 2024-09-06 Ziwen Huang , Taeyoon Kim , Tanay Roy , Yao Lu , Alexander Romanenko , Shaojiang Zhu , Anna Grassellino

Superconducting qubits offer an unprecedentedly high degree of flexibility in terms of circuit encoding and parameter choices. However, in designing the qubit parameters one typically faces the conflicting goals of long coherence times and…

Quantum Physics · Physics 2025-04-08 C. A. Siegele , A. A. Sokolova , L. N. Kapoor , F. Hassani , J. M. Fink

Spin qubits in semiconducting quantum dots are currently limited by slow readout processes, which are orders of magnitude slower than gate operations. In contrast, Andreev spin qubits benefit from fast measurement schemes enabled by the…

Mesoscale and Nanoscale Physics · Physics 2025-06-25 Michèle Jakob , Katharina Laubscher , Patrick Del Vecchio , Anasua Chatterjee , Valla Fatemi , Stefano Bosco

A major challenge for scaling up superconducting quantum computers is unwanted couplings between qubits, which lead to always-on ZZ couplings that impact gate fidelities by shifting energy levels conditional on qubit states. To tackle this…

Quantum Physics · Physics 2024-12-30 Simon Pettersson Fors , Jorge Fernández-Pendás , Anton Frisk Kockum

We propose and analyse a scheme for performing a long-range entangling gate for qubits encoded in electron spins trapped in semiconductor quantum dots. Our coupling makes use of an electrostatic interaction between the state-dependent…

Mesoscale and Nanoscale Physics · Physics 2017-09-07 Samuel J. Elman , Stephen D. Bartlett , Andrew C. Doherty

A quantum computer will use the properties of quantum physics to solve certain computational problems much faster than otherwise possible. One promising potential implementation is to use superconducting quantum bits in the circuit quantum…

Quantum Physics · Physics 2013-12-01 Matthew Reed

High-fidelity gate operations are essential to the realization of a fault-tolerant quantum computer. In addition, the physical resources required to implement gates must scale efficiently with system size. A longstanding goal of the…

Protected superconducting qubits such as the $0$-$\pi$ qubit promise to substantially reduce physical error rates. However, a key challenge in the field is designing gates for these qubits that do not compromise their protection, or become…

Quantum Physics · Physics 2026-01-16 Xanda C Kolesnikow , Thomas B Smith , Felix Thomsen , Abhijeet Alase , Andrew C Doherty

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…

Superconducting quantum processors offer a promising path towards practical quantum computing. However, building a fault-tolerant quantum computer with millions of superconducting qubits is hindered by wiring density, packaging constraints…

Quantum Physics · Physics 2025-05-14 Jiajian Zhang , Ji Chu , Jingjing Niu , Youpeng Zhong , Dapeng Yu

We demonstrate a quantum error correction scheme that protects against accidental measurement, using an encoding where the logical state of a single qubit is encoded into two physical qubits using a non-deterministic photonic CNOT gate. For…

Quantum Physics · Physics 2008-11-26 J. L. O'Brien , G. J. Pryde , A. G. White , T. C. Ralph

We present a gradient-based method to construct high-fidelity, two-qubit quantum gates in a system consisting of two transmon qubits coupled via a tunable coupler. In particular, we focus on single flux quantum (SFQ) pulses as a promising…