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We demonstrate new experimental procedures for measuring small errors in a superconducting quantum bit (qubit). By carefully separating out gate and measurement errors, we construct a complete error budget and demonstrate single qubit gate…

We demonstrate a two-qubit logic gate driven by near-field microwaves in a room-temperature microfabricated ion trap. We measure a gate fidelity of 99.7(1)\%, which is above the minimum threshold required for fault-tolerant quantum…

Quantum Physics · Physics 2016-10-05 T. P. Harty , M. A. Sepiol , D. T. C. Allcock , C. J. Ballance , J. E. Tarlton , D. M. Lucas

We present a strategy for producing multi-qubit gates that promise high fidelity with minimal tuning requirements. Our strategy combines gap protection from the adiabatic theorem with dynamical decoupling in a complementary manner. To avoid…

Quantum Physics · Physics 2015-10-23 Wayne M. Witzel , Inès Montaño , Richard P. Muller , Malcolm S. Carroll

Generating high-fidelity, tunable entanglement between qubits is crucial for realizing gate-based quantum computation. In superconducting circuits, tunable interactions are often implemented using flux-tunable qubits or coupling elements,…

We propose a scheme for entanglement distribution among different single atoms trapped in separated cavities. In our scheme, by reflecting an input coherent optical pulse from a cavity with a single trapped atom, a controlled phase-shift…

Quantum Physics · Physics 2019-02-25 Feng Mei , Ya-Fei Yu , Xun-Li Feng , Zhi-Ming Zhang , C. H. Oh

We propose a general approach to implement nonadiabatic geometric single- and two-qubit gates beyond the rotating wave approximation (RWA). This protocol is compatible with most optimal control methods used in previous RWA protocols; thus,…

Quantum Physics · Physics 2022-12-22 Ye-Hong Chen , Adam Miranowicz , Xi Chen , Yan Xia , Franco Nori

Scalable superconducting quantum processors require balancing critical constraints in coherence, control complexity, and spectral crowding. Fixed-frequency architectures suppress flux noise and simplify control via all-microwave operations…

Quantum Physics · Physics 2025-10-17 Kui Zhao , Wei-Guo Ma , Ziting Wang , Hao Li , Kaixuan Huang , Yun-Hao Shi , Kai Xu , Heng Fan

We describe a simple entangling principle based on the scattering of photons off single emitters in one-dimensional waveguides (or extremely-lossy cavities). The scheme can be applied to photonic qubits encoded in polarization or time-bin,…

Quantum Physics · Physics 2012-11-28 Ying Li , Leandro Aolita , Darrick E. Chang , Leong Chuan Kwek

We study the entanglement properties of randomized mixed hypergraph states, extending the concept of randomized mixed graph states to encompass hypergraph-based quantum states. In our model, imperfect generalized multi-qubit gates are…

Quantum Physics · Physics 2026-04-13 Vinícius Salem , Alison A. Silva , Fabiano M. Andrade

Superconducting qubits, a promising candidate for universal quantum computing, currently face limitations in chip size due to reproducibility, wiring complexity, and packaging modes. Distributed quantum modules offer a viable strategy for…

Realizing the theoretical promise of quantum computers will require overcoming decoherence. Here we demonstrate numerically that high fidelity quantum gates are possible within a framework of quantum dynamical decoupling. Orders of…

Quantum Physics · Physics 2010-12-16 Jacob R. West , Daniel A. Lidar , Bryan H. Fong , Mark F. Gyure

For quantum computation using photons, performing deterministic quantum gate operations is a challenge due to the probabilistic nature of the photon-photon interaction. Encoding qubits in multiple degrees-of-freedom of photons and…

Quantum Physics · Physics 2025-08-28 Kanad Sengupta , S. P. Dinesh , K. Muhammed Shafi , Soumya Asokan , C. M. Chandrashekar

Using geometric phases to realize noise-resilient quantum computing is an important method to enhance the control fidelity. In this work, we experimentally realize a universal nonadiabatic geometric quantum gate set in a superconducting…

High-fidelity entangling gates are essential for quantum computation. Currently, most approaches to designing such gates are based either on simple, analytical pulse waveforms or on ones obtained from numerical optimization techniques. In…

Quantum Physics · Physics 2023-09-15 Ho Lun Tang , Kyle Connelly , Ada Warren , Fei Zhuang , Sophia E. Economou , Edwin Barnes

In a large scale trapped atomic ion quantum computer, high-fidelity two-qubit gates need to be extended over all qubits with individual control. We realize and characterize high-fidelity two-qubit gates in a system with up to 4 ions using…

Near-term quantum computers are primarily limited by errors in quantum operations (or gates) between two quantum bits (or qubits). A physical machine typically provides a set of basis gates that include primitive 2-qubit (2Q) and 1-qubit…

An entanglement-generating protocol is described for two qubits coupled to a cavity field in the bad-cavity limit. By measuring the amplitude of a field transmitted through the cavity, an entangled spin-singlet state can be established…

Quantum Physics · Physics 2015-06-04 Brian Julsgaard , Klaus Mølmer

Qudit, a high-dimensional quantum system, provides a larger Hilbert space to process the quantum information and has shown remarkable advantages over the qubit counterparts. It is a great challenge to realize the high fidelity universal…

Quantum Physics · Physics 2023-12-01 Zhe Meng , Wen-Qiang Liu , Bo-Wen Song , Xiao-Yun Wang , An-Ning Zhang , Zhang-Qi Yin

Quantum entanglement is a key resource for quantum computation and quantum communication \cite{Nielsen2010}. Scaling to large quantum communication or computation networks further requires the deterministic generation of multi-qubit…