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Variational hybrid quantum-classical algorithms (VHQCAs) are near-term algorithms that leverage classical optimization to minimize a cost function, which is efficiently evaluated on a quantum computer. Recently VHQCAs have been proposed for…

Quantum Physics · Physics 2020-04-07 Kunal Sharma , Sumeet Khatri , M. Cerezo , Patrick J. Coles

The variational quantum eigensolver (VQE) has emerged as one of the leading quantum algorithms for solving electronic structure problems on near-term noisy intermediate-scale quantum devices. However, its practical application to quantum…

Chemical Physics · Physics 2026-03-24 Yanxian Tao , Lingyun Wan , Jie Liu

We address a wide spectrum of quantum control strategies, including various open-loop protocols and advanced adaptive methods. These methodologies apply to few-qubit scenarios and naturally scale to larger N-qubit systems. We benchmark them…

Quantum Physics · Physics 2025-09-22 Atta ur Rahman , M. Y. Abd-Rabbou , Cong-feng Qiao

Combinatorial optimization on near-term quantum devices is a promising path to demonstrating quantum advantage. However, the capabilities of these devices are constrained by high noise or error rates. In this paper, we propose an iterative…

Quantum Physics · Physics 2022-05-12 Xiaoyuan Liu , Anthony Angone , Ruslan Shaydulin , Ilya Safro , Yuri Alexeev , Lukasz Cincio

Variational quantum algorithms are tailored to perform within the constraints of current quantum devices, yet they are limited by performance-degrading errors. In this study, we consider a noise model that reflects realistic gate errors…

Quantum errors in noisy environments remain a major obstacle to advancing quantum information technology. In this work, we expand a recently developed geometric framework, originally utilized for analyzing noise accumulation and creating…

Quantum Physics · Physics 2024-07-11 Junkai Zeng , Yong-Ju Hai , Hao Liang , Xiu-Hao Deng

We address the experimentally relevant problem of robust mitigation of dephasing noise acting on a qubit. We first present an extension of a method for representing $1/\omega^{\alpha}$ noise developed by Kuopanportti et al. to the efficient…

Quantum Physics · Physics 2010-06-01 Kevin C. Young , Dylan J Gorman , K. Birgitta Whaley

Quantum algorithms have been proposed to accelerate the simulation of the chaotic dynamical systems that are ubiquitous in the physics of plasmas. Quantum computers without error correction might even use noise to their advantage to…

Quantum Physics · Physics 2025-04-22 Max D. Porter , Ilon Joseph

Quantum Variational Circuits (QVCs) are often claimed as one of the most potent uses of both near term and long term quantum hardware. The standard approaches to optimizing these circuits rely on a classical system to compute the new…

Quantum Physics · Physics 2022-02-11 Owen Lockwood

Quantum computers promise to revolutionize our ability to simulate molecules, and cloud-based hardware is becoming increasingly accessible to a wide body of researchers. Algorithms such as Quantum Phase Estimation and the Variational…

Quantum Physics · Physics 2021-12-21 Kyle Sherbert , Frank Cerasoli , Marco Buongiorno Nardelli

We investigate optimized quantum state preparation for quantum metrology applications in noisy environments. Using the QFI-Opt package, we simulate a low-depth variational quantum circuit (VQC) composed of a sequence of global rotations and…

Noisy quantum simulation is challenging since one has to take into account the stochastic nature of the process. The dominating method for it is the density matrix approach. In this paper, we evaluate conditions for which this method is…

Quantum Physics · Physics 2022-10-31 William Berquist , Danylo Lykov , Minzhao Liu , Yuri Alexeev

State preparation is a cornerstone of quantum technologies, underpinning applications in computation, communication, and sensing. Its importance becomes even more pronounced in non-Markovian open quantum systems, where environmental memory…

Quantum Physics · Physics 2026-05-29 Ritik Sareen , Akram Youssry , Alberto Peruzzo

We apply a graybox machine-learning framework to model and control a qubit undergoing Markovian and non-Markovian dynamics from environmental noise. The approach combines physics-informed equations with a lightweight transformer neural…

We present a scheme for implementing quantum operations with superconducting qubits. Our approach uses a "coupler" qubit to mediate a controllable, secular interaction between "data" qubits, pulse sequences which strongly mitigate the…

Quantum Physics · Physics 2013-10-22 Andrew J. Kerman , William D. Oliver

We demonstrate a robust quantum control framework that enables high-fidelity gate operations in semiconductor spin qubit systems with always-on couplings. Always-on interactions between qubits pose a fundamental challenge for quantum…

Quantum Physics · Physics 2025-03-18 Yong-Ju Hai , Shihang Zhang , Haoyu Guan , Peihao Huang , Yu He , Xiu-Hao Deng

Evaluating the reliability of noisy quantum circuits is essential for implementing quantum algorithms on noisy quantum devices. However, current quantum hardware exhibits diverse noise mechanisms whose compounded effects make accurate and…

Quantum Physics · Physics 2026-02-23 Jindi Wu , Tianjie Hu , Qun Li

As a hybrid quantum-classical algorithm, the variational quantum eigensolver is widely applied in quantum chemistry simulations, especially in computing the electronic structure of complex molecular systems. However, on existing noisy…

Quantum Physics · Physics 2025-01-28 Wanqi Sun , Jungang Xu , Chenghua Duan

Hybridizing different physical systems or degrees of freedom offers significant advantages for realizing practical, universal, scalable, and fault-tolerant quantum computation (FTQC). Here, we propose optical FTQC schemes with low squeezing…

Quantum Physics · Physics 2025-03-27 Peilin Du

In realistic hardware for quantum computation that possesses fault-tolerance, non-stationary noise and stochastic drift lead to logical failure from the temporal accumulation of errors, not from independent events. Static decoding and fixed…

Quantum Physics · Physics 2026-03-17 Tirtha Haque