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Variational Quantum Algorithms (VQAs) are a class of hybrid quantum-classical algorithms that leverage on classical optimization tools to find the optimal parameters for a parameterized quantum circuit. One relevant application of VQAs is…

Quantum Physics · Physics 2026-01-26 Mirko Legnini , Julian Berberich

Quantum Computing aims to streamline machine learning, making it more effective with fewer trainable parameters. This reduction of parameters can speed up the learning process and reduce the use of computational resources. However, in the…

Quantum Physics · Physics 2024-05-22 Michael Kölle , Timo Witter , Tobias Rohe , Gerhard Stenzel , Philipp Altmann , Thomas Gabor

Applications such as simulating complicated quantum systems or solving large-scale linear algebra problems are very challenging for classical computers due to the extremely high computational cost. Quantum computers promise a solution,…

We propose an algorithm for variational quantum algorithms (VQAs) to optimize the structure of parameterized quantum circuits (PQCs) efficiently. The algorithm optimizes the PQC structure on-the-fly in VQA by sequentially replacing a…

Quantum Physics · Physics 2024-05-17 Kaito Wada , Rudy Raymond , Yuki Sato , Hiroshi C. Watanabe

Variational quantum circuits (VQCs) are an essential tool in applying noisy intermediate-scale quantum computers to practical problems. VQCs are used as a central component in many algorithms, for example, in quantum machine learning,…

Quantum Physics · Physics 2025-12-18 Joona V. Pankkonen , Lauri Ylinen , Matti Raasakka , Ilkka Tittonen

Variational quantum algorithms (VQAs) are expected to be a path to quantum advantages on noisy intermediate-scale quantum devices. However, both empirical and theoretical results exhibit that the deployed ansatz heavily affects the…

Quantum Physics · Physics 2022-05-31 Yuxuan Du , Tao Huang , Shan You , Min-Hsiu Hsieh , Dacheng Tao

The variational quantum eigensolver is a prominent hybrid quantum-classical algorithm expected to impact near-term quantum devices. They are usually based on a circuit ansatz consisting of parameterized single-qubit gates and fixed…

Quantum Physics · Physics 2022-10-13 S. E. Rasmussen , N. T. Zinner

Current structure optimization algorithms optimize the structure of quantum circuit from scratch for each new task of variational quantum algorithms (VQAs) without using any prior experience, which is inefficient and time-consuming.…

Quantum Physics · Physics 2022-04-12 Chuangtao Chen , Zhimin He , Shenggen Zheng , Yan Zhou , Haozhen Situ

With the advent of hybrid quantum classical algorithms using parameterized quantum circuits the question of how to optimize these algorithms and circuits emerges. In this paper we show that the number of single-qubit rotations in…

Quantum Physics · Physics 2020-10-29 S. E. Rasmussen , N. J. S. Loft , T. Bækkegaard , M. Kues , N. T. Zinner

For a large number of tasks, quantum computing demonstrates the potential for exponential acceleration over classical computing. In the NISQ era, variable-component subcircuits enable applications of quantum computing. To reduce the…

Quantum Physics · Physics 2022-12-12 Junhan Qin

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…

In recent years, Variational Quantum Algorithms (VQAs) have emerged as a promising approach for solving optimization problems on quantum computers in the NISQ era. However, one limitation of VQAs is their reliance on fixed-structure…

Quantum Physics · Physics 2026-03-03 Gloria Turati , Maurizio Ferrari Dacrema , Paolo Cremonesi

Quantum variational circuits have gained significant attention due to their applications in the quantum approximate optimization algorithm and quantum machine learning research. This work introduces a novel class of classical probabilistic…

Quantum Physics · Physics 2025-09-17 Gal Weitz , Lirandë Pira , Chris Ferrie , Joshua Combes

Solving optimization problems using variational algorithms stands out as a crucial application for noisy intermediate-scale devices. Instead of constructing gate-based quantum computers, our focus centers on designing variational quantum…

Quantum Physics · Physics 2024-07-18 Yapeng Wang , Yongcheng Ding , Francisco Andrés Cárdenas-López , Xi Chen

A key open question in quantum computing is whether quantum algorithms can potentially offer a significant advantage over classical algorithms for tasks of practical interest. Understanding the limits of classical computing in simulating…

Quantum Physics · Physics 2021-06-23 Matija Medvidovic , Giuseppe Carleo

Quantum enhanced optimization of classical cost functions is a central theme of quantum computing due to its high potential value in science and technology. The variational quantum eigensolver (VQE) and the quantum approximate optimization…

Quantum Physics · Physics 2024-11-27 Giuseppe Scriva , Nikita Astrakhantsev , Sebastiano Pilati , Guglielmo Mazzola

Recent research has shown that wavefunction evolution in real- and imaginary-time can generate quantum subspaces with significant utility for obtaining accurate ground state energies. Inspired by these methods, we propose combining quantum…

In variational quantum algorithms, parameterization is typically applied to single-qubit gates.In this study, we instead parameterize a generalized controlled gate and propose an algorithm to locally minimize the cost function by maximally…

The variational quantum eigensolver (or VQE) uses the variational principle to compute the ground state energy of a Hamiltonian, a problem that is central to quantum chemistry and condensed matter physics. Conventional computing methods are…

Variational quantum algorithms (VQAs) have emerged as a promising near-term technique to explore practical quantum advantage on noisy intermediate-scale quantum (NISQ) devices. However, the inefficient parameter training process due to the…

Quantum Physics · Physics 2023-05-24 Yun-Fei Niu , Shuo Zhang , Chen Ding , Wan-Su Bao , He-Liang Huang