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Variational Quantum algorithms, especially Quantum Approximate Optimization and Variational Quantum Eigensolver (VQE) have established their potential to provide computational advantage in the realm of combinatorial optimization. However,…

Quantum Physics · Physics 2023-07-11 Dheeraj Peddireddy , Utkarsh Priyam , Vaneet Aggarwal

Given a parameterized quantum circuit such that a certain setting of these real-valued parameters corresponds to Grover's celebrated search algorithm, can a variational algorithm recover these settings and hence learn Grover's algorithm? We…

Quantum Physics · Physics 2019-01-02 Mauro E. S. Morales , Timur Tlyachev , Jacob Biamonte

Diagrammatic representations of quantum algorithms and circuits offer novel approaches to their design and analysis. In this work, we describe extensions of the ZX-calculus especially suitable for parameterized quantum circuits, in…

Quantum Physics · Physics 2023-11-16 Tobias Stollenwerk , Stuart Hadfield

Currently available quantum hardware allows for small scale implementations of quantum machine learning algorithms. Such experiments aid the search for applications of quantum computers by benchmarking the near-term feasibility of candidate…

Quantum Physics · Physics 2021-09-08 Michael R. Geller , Zoë Holmes , Patrick J. Coles , Andrew Sornborger

Parameter shift rules (PSRs) are key techniques for efficient gradient estimation in variational quantum eigensolvers (VQEs). In this paper, we propose its Bayesian variant, where Gaussian processes with appropriate kernels are used to…

Machine Learning · Computer Science 2026-05-07 Samuele Pedrielli , Christopher J. Anders , Lena Funcke , Karl Jansen , Kim A. Nicoli , Shinichi Nakajima

We propose an adaptive quantum algorithm to prepare accurate variational time evolved wave functions. The method is based on the projected Variational Quantum Dynamics (pVQD) algorithm, that performs a global optimization with linear…

Quantum Physics · Physics 2025-02-20 David Linteau , Stefano Barison , Netanel Lindner , Giuseppe Carleo

Generalized eigenvalue problems (GEPs) play an important role in the variety of fields including engineering, machine learning and quantum chemistry. Especially, many problems in these fields can be reduced to finding the minimum or maximum…

Parameterized quantum circuits have been extensively used as the basis for machine learning models in regression, classification, and generative tasks. For supervised learning, their expressivity has been thoroughly investigated and several…

Quantum Physics · Physics 2026-05-20 Alice Barthe , Michele Grossi , Sofia Vallecorsa , Jordi Tura , Vedran Dunjko

This Ph.D. thesis provides a comprehensive review of the state-of-the-art in the field of Variational Quantum Algorithms and Quantum Machine Learning, including numerous original contributions. The first chapters are devoted to a brief…

Quantum Physics · Physics 2023-06-19 Stefano Mangini

We introduce a new scheme for quantum circuit design called controlled gate networks. Rather than trying to reduce the complexity of individual unitary operations, the new strategy is to toggle between all of the unitary operations needed…

We propose a hybrid quantum-classical approach to model continuous classical probability distributions using a variational quantum circuit. The architecture of the variational circuit consists of two parts: a quantum circuit employed to…

Quantum Physics · Physics 2019-01-04 Jonathan Romero , Alan Aspuru-Guzik

Variational hybrid quantum-classical algorithms are promising candidates for near-term implementation on quantum computers. In these algorithms, a quantum computer evaluates the cost of a gate sequence (with speedup over classical cost…

Quantum Physics · Physics 2019-06-27 Ryan LaRose , Arkin Tikku , Étude O'Neel-Judy , Lukasz Cincio , Patrick J. Coles

We present explicit expressions for the central piece of a variational method developed by Shi et al. which extends variational wave functions that are efficiently computable on classical computers beyond mean-field to generalized Gaussian…

Quantum Physics · Physics 2021-09-23 Michael P. Kaicher , Simon B. Jäger , Frank K. Wilhelm

This research extends quantum singular value transformation (QSVT) for general bounded operators embedded in unitary operators on possibly infinite-dimensional Hilbert spaces. Through in-depth mathematical exploration, we have achieved a…

Quantum Physics · Physics 2024-01-18 Chusei Kiumi , Akito Suzuki

Quantum algorithms for diverse problems, including search and optimization problems, require the implementation of a reflection operator over a target state. Commonly, such reflections are approximately implemented using phase estimation.…

Quantum Physics · Physics 2018-03-08 Anirban Narayan Chowdhury , Yigit Subasi , Rolando D. Somma

Despite extensive research efforts, few quantum algorithms for classical optimization demonstrate realizable quantum advantage. The utility of many quantum algorithms is limited by high requisite circuit depth and nonconvex optimization…

Quantum Physics · Physics 2022-01-27 Taylor L. Patti , Jean Kossaifi , Anima Anandkumar , Susanne F. Yelin

The generalized eigenvalue (GE) problems are of particular importance in various areas of science engineering and machine learning. We present a variational quantum algorithm for finding the desired generalized eigenvalue of the GE problem,…

Quantum Physics · Physics 2022-03-08 Jin-Min Liang , Shu-Qian Shen , Ming Li , Shao-Ming Fei

Classical optimization is a cornerstone of the success of variational quantum algorithms, which often require determining the derivatives of the cost function relative to variational parameters. The computation of the cost function and its…

Quantum Physics · Physics 2025-07-15 Muhammad Umer , Eleftherios Mastorakis , Dimitris G. Angelakis

Unitary and non-unitary diagonal operators are fundamental building blocks in quantum algorithms with applications in the resolution of partial differential equations, Hamiltonian simulations, the loading of classical data on quantum…

Quantum Physics · Physics 2025-01-22 Julien Zylberman , Ugo Nzongani , Andrea Simonetto , Fabrice Debbasch

We show that randomly choosing the matrices in a completely positive map from the unitary group gives a quantum expander. We consider Hermitian and non-Hermitian cases, and we provide asymptotically tight bounds in the Hermitian case on the…

Quantum Physics · Physics 2009-11-13 M. B. Hastings