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Reducing circuit depth is essential for implementing quantum simulations of electronic structure on near-term quantum devices. In this work, we propose a variational quantum eigensolver (VQE) based perturbation theory algorithm to…

Quantum Physics · Physics 2024-01-17 Jie Liu , Zhenyu Li , Jinlong Yang

Quantum computing presents a promising path toward precise quantum chemical simulations, particularly for systems that challenge classical methods. This work investigates the performance of the Variational Quantum Eigensolver (VQE) in…

Quantum Physics · Physics 2025-10-28 Zakaria Boutakka , Nouhaila Innan , Muhammed Shafique , Mohamed Bennai , Z. Sakhi

Variational quantum eigensolvers (VQEs) are among the most promising quantum algorithms for solving electronic structure problems in quantum chemistry, particularly during the Noisy Intermediate-Scale Quantum (NISQ) era. In this study, we…

Quantum Physics · Physics 2026-05-07 Abel Carreras , David Casanova , Román Orús

Although the simulation of quantum chemistry is one of the most anticipated applications of quantum computing, the scaling of known upper bounds on the complexity of these algorithms is daunting. Prior work has bounded errors due to…

Quantum Physics · Physics 2015-03-05 Ryan Babbush , Jarrod McClean , Dave Wecker , Alán Aspuru-Guzik , Nathan Wiebe

In this work, we introduce a correction to the unitary coupled cluster method with single and double excitations (UCCSD) that incorporates the effects of missing triple excitations through a treatment that is correct through fifth-order in…

Chemical Physics · Physics 2025-09-08 Zachary W. Windom , Daniel Claudino

The time evolution operator plays a crucial role in the precise computation of chemical experiments on quantum computers and holds immense promise for advancing the fields of physical and computer sciences, with applications spanning…

The recent quantum information boom has effected a resurgence of interest in unitary coupled cluster (UCC) theory. Our group's interest in local energy landscapes of unitary ans\"atze prompted us to investigate the classical approach of…

Chemical Physics · Physics 2022-11-01 Harper R. Grimsley , Nicholas J. Mayhall

In this work we investigate methods to improve the efficiency and scalability of quantum algorithms for quantum chemistry applications. We propose a transformation of the electronic structure Hamiltonian in the second quantization framework…

We propose a variational alternative to the Trotter-Suzuki decomposition that provides greater control over errors while preserving the unitary structure of time evolution. The variational parameters in our ansatz are derived from a global…

Quantum Physics · Physics 2025-11-20 Ibsal Assi , Michael Vogl , Meenu Kumari , J. P. F. LeBlanc

Unitary Coupled Cluster (UCC) approaches are an appealing route to utilising quantum hardware to perform quantum chemistry calculations, as quantum computers can in principle perform UCC calculations in a polynomially scaling fashion, as…

Quantum Physics · Physics 2022-06-15 Maria-Andreea Filip , Nathan Fitzpatrick , David Muñoz Ramo , Alex J. W. Thom

The adaptive derivative-assembled pseudo-trotter variational quantum eigensolver (ADAPT-VQE) is a promising hybrid quantum-classical algorithm for molecular ground state energy calculation, yet its practical scalability is hampered by…

Quantum Physics · Physics 2026-02-05 Runhong He , Xin Hong , Qiaozhen Chai , Ji Guan , Junyuan Zhou , Arapat Ablimit , Guolong Cui , Shenggang Ying

The adaptive derivative-assembled problem-tailored variational quantum eigensolver (ADAPT-VQE) is one of the most widely used algorithms for electronic structure calculations in quantum computers. It adaptively selects operators based on…

Chemical Physics · Physics 2025-08-29 Nonia Vaquero-Sabater , Abel Carreras , David Casanova

In Coupled-Cluster (CC) theory, unphysical complex energies may arise in the presence of strong magnetic fields, near conical intersections, or in systems exhibiting complex Abelian point group symmetries. This issue originates from the…

Chemical Physics · Physics 2025-07-28 Laura Grazioli , Marios-Petros Kitsaras , Stella Stopkowicz

We propose an efficient ${\cal O}(N^2)$-parameter ansatz that consists of a sequence of exponential operators, each of which is a unitary variant of Neuscamman's cluster Jastrow operator. The ansatz can also be derived as a decomposition of…

Chemical Physics · Physics 2020-07-07 Yuta Matsuzawa , Yuki Kurashige

Variational quantum algorithms are a promising hybrid framework for solving chemistry and physics problems with broad applicability to optimization as well. They are particularly well suited for noisy intermediate scale quantum (NISQ)…

Quantum Physics · Physics 2021-02-18 Lucas Slattery , Benjamin Villalonga , Bryan K. Clark

A major difficulty in quantum simulation is the adequate treatment of a large collection of entangled particles, synonymous with electron correlation in electronic structure theory, with coupled cluster (CC) theory being the leading…

Chemical Physics · Physics 2024-06-06 Zachary W. Windom , Daniel Claudino , Rodney J. Bartlett

Solving molecular energy levels via the Variational Quantum Eigensolver (VQE) algorithm represents one of the most promising applications for demonstrating practically meaningful quantum advantage in the noisy intermediate-scale quantum…

Chemical Physics · Physics 2025-12-25 Runhong He , Arapat Ablimit , Xin Hong , Qiaozhen Chai , Junyuan Zhou , Ji Guan , Guolong Cui , Shenggang Ying

Quantum mechanics has introduced a new theoretical framework for the study of molecules, enabling the prediction of properties and dynamics through the solution of the Schr\"odinger equation applied to these systems. However, solving this…

The hardware requirements of useful quantum algorithms remain unmet by the quantum computers available today. Because it was designed to soften these requirements, the Variational Quantum Eigensolver (VQE) has gained popularity as a…

Quantum Physics · Physics 2022-12-09 Mafalda Ramôa

We describe a compilation strategy for Variational Quantum Eigensolver (VQE) algorithms which use the Unitary Coupled Cluster (UCC) ansatz, designed to reduce circuit depth and gate count. This is achieved by partitioning Pauli exponential…

Quantum Physics · Physics 2020-08-28 Alexander Cowtan , Will Simmons , Ross Duncan