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We consider stability of a general quantum algorithm with respect to a fixed but unknown residual interaction between qubits, and show a surprising fact, namely that the average fidelity of quantum computation increases by decreasing…

Quantum Physics · Physics 2009-11-07 Tomaz Prosen , Marko Znidaric

To employ a quantum device, the performance of the quantum gates in the device needs to be evaluated first. Since the dimensionality of a quantum gate grows exponentially with the number of qubits, evaluating the performance of a quantum…

Quantum Physics · Physics 2022-02-14 Maolin Luo , Xiaoqian Zhang , Xiaoqi Zhou

We provide an analytic way to implement any arbitrary two-qubit unitary operation, given an entangling two-qubit gate together with local gates. This is shown to provide explicit construction of a universal quantum circuit that exactly…

Quantum Physics · Physics 2009-11-07 Jun Zhang , Jiri Vala , Shankar Sastry , K. Birgitta Whaley

Fidelity is a fundamental measure for the closeness of two quantum states, which is important both from a theoretical and a practical point of view. Yet, in general, it is difficult to give good estimates of fidelity, especially when one…

Quantum Physics · Physics 2022-03-31 András Gilyén , Alexander Poremba

Direct multi-qubit gates are becoming critical to facilitate quantum computations in near-term devices by reducing the gate counts and circuit depth. Here, we demonstrate that fast and high fidelity three-qubit gates can be realized in a…

Mesoscale and Nanoscale Physics · Physics 2025-07-10 Minh T. P. Nguyen , Maximilian Rimbach-Russ , Lieven M. K. Vandersypen , Stefano Bosco

Quantum logic gates can perform calculations much more efficiently than their classical counterparts. However, the level of control needed to obtain a reliable quantum operation is correspondingly higher. In order to evaluate the…

Quantum Physics · Physics 2009-11-13 Holger F. Hofmann , Ryo Okamoto , Shigeki Takeuchi

Universal quantum computation will require qubit technology based on a scalable platform, together with quantum error correction protocols that place strict limits on the maximum infidelities for one- and two-qubit gate operations. While a…

Geometric phase is a promising element to induce high-fidelity and robust quantum operations due to its built-in noise-resilience feature. Unfortunately, its practical applications are usually circumscribed by requiring complex interactions…

Quantum Physics · Physics 2020-12-08 Tao Chen , Zheng-Yuan Xue

We present quantum fidelity benchmarks for continuous-variable (CV) quantum devices to outperform quantum channels which can transmit at most $k$-dimensional coherences for positive integers $k$. We determine an upper bound of an average…

Quantum Physics · Physics 2016-06-06 Ryo Namiki

Because of their long coherence time and compatibility with industrial foundry processes, electron spin qubits are a promising platform for scalable quantum processors. A full-fledged quantum computer will need quantum error correction,…

A universal squeezing gate capable of squeezing arbitrary input states is essential for continuous-variable quantum computation~\cite{PRA79062318,PRL112120504}. However, in present state-of-the-art…

Quantum Physics · Physics 2020-06-02 Jie Zhao , Kui Liu , Jeng Hao , Mile Gu , Jayne Thompson , Ping Koy Lam , Syed Assad

Rigorously establishing that the error in an experimental quantum operation is beneath the threshold for fault-tolerant quantum computation currently requires considering the worst-case error, which can be orders of magnitude smaller than…

Quantum Physics · Physics 2016-11-02 Joel J. Wallman

Fault-tolerant quantum computers which can solve hard problems rely on quantum error correction. One of the most promising error correction codes is the surface code, which requires universal gate fidelities exceeding the error correction…

We present a simple scheme for implementing an atomic phase gate using two degrees of freedom for each atom and discuss its realization with cold rubidium atoms on atom chips. We investigate the performance of this collisional phase gate…

Quantum Physics · Physics 2009-11-11 M. A. Cirone , A. Negretti , T. Calarco , P. Krueger , J. Schmiedmayer

The native gate set is fundamental to the performance of quantum devices, as it governs the accuracy of basic quantum operations and dictates the complexity of implementing quantum algorithms. Traditional approaches to extending gate sets…

We describe a simple randomized benchmarking protocol for quantum information processors and obtain a sequence of models for the observable fidelity decay as a function of a perturbative expansion of the errors. We are able to prove that…

Quantum Physics · Physics 2011-06-14 Easwar Magesan , J. M. Gambetta , Joseph Emerson

Electron spins in semiconductors are promising qubits because their long coherence times enable nearly 10^9 coherent quantum gate operations. However, developing a scalable high-fidelity two-qubit gate remains challenging. Here, we…

Mesoscale and Nanoscale Physics · Physics 2016-08-16 John M. Nichol , Lucas A. Orona , Shannon P. Harvey , Saeed Fallahi , Geoffrey C. Gardner , Michael J. Manfra , Amir Yacoby

We present a comprehensive analysis of fidelity decay and error accumulation in faulty quantum circuit models. Our work devises an analytical bound for the average fidelity between desired and faulty output states, accounting for errors…

In present work, we shall develope a protocol to estimate the average fidelity for the bipartite system. We show that the average fidelity should be known if the three measurable quantities, the average survive probability of the product…

Quantum Physics · Physics 2015-09-30 Long Huang , Xiaohua Wu

Quantum computers can in principle simulate quantum physics exponentially faster than their classical counterparts, but some technical hurdles remain. Here we consider methods to make proposed chemical simulation algorithms computationally…

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