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We present two techniques that can greatly reduce the number of gates required to realize an energy measurement, with application to ground state preparation in quantum simulations. The first technique realizes that to prepare the ground…

Quantum Physics · Physics 2018-08-28 David Poulin , Alexei Kitaev , Damian S. Steiger , Matthew B. Hastings , Matthias Troyer

We propose a new approach to improve the accuracy of ground state estimates in Variational Quantum Eigensolver (VQE) algorithms by employing subspace representations with soft-coded orthogonality constraints. As in other subspace-based VQE…

Quantum Physics · Physics 2026-02-19 Giuseppe Clemente , Marco Intini

The contextual subspace variational quantum eigensolver (CS-VQE) is a hybrid quantum-classical algorithm that approximates the ground-state energy of a given qubit Hamiltonian. It achieves this by separating the Hamiltonian into contextual…

Quantum Physics · Physics 2023-02-14 Alexis Ralli , Tim Weaving , Andrew Tranter , William M. Kirby , Peter J. Love , Peter V. Coveney

Recent advances in quantum computing devices have brought attention to hybrid quantum-classical algorithms like the Variational Quantum Eigensolver (VQE) as a potential route to practical quantum advantage in chemistry. However, it is not…

The calculation of excited state energies of electronic structure Hamiltonians has many important applications, such as the calculation of optical spectra and reaction rates. While low-depth quantum algorithms, such as the variational…

Quantum Physics · Physics 2019-07-03 Oscar Higgott , Daochen Wang , Stephen Brierley

The state-of-the-art quantum computing hardware has entered the noisy intermediate-scale quantum (NISQ) era. Having been constrained by the limited number of qubits and shallow circuit depth, NISQ devices have nevertheless demonstrated the…

Quantum Physics · Physics 2022-06-23 Guanglei Xu , Yi-Bin Guo , Xuan Li , Zong-Sheng Zhou , Hai-Jun Liao , T. Xiang

Quantum Mechanical ground states of many-body systems can be important resources for various investigations: for quantum sensing, as the initial state for nonequilibrium quantum dynamics following quenches, and the simulation of quantum…

Quantum Physics · Physics 2025-11-18 Prashasti Tiwari , Dylan Lewis , Sougato Bose

To understand the properties and interactions of materials, and determining the ground state energies is one of the important challenges in quantum chemistry, materials science, and quantum mechanics, where quantum computing can play an…

Quantum Physics · Physics 2025-04-15 Badie Ghavami , Forouzan Mirmasoudi

The many-body nature of nuclear physics problems poses significant computational challenges. These challenges become even more pronounced when studying the resonance states of nuclear systems, which are governed by the non-Hermitian…

Quantum Physics · Physics 2025-04-17 Ashutosh Singh , Pooja Siwach , P. Arumugam

We present a fully digital approach for simulating single-mode squeezed states on a superconducting quantum processor using an enhanced bosonic encoding strategy. By mapping up to 2^{n} photonic Fock states onto n qubits, our framework…

Quantum Physics · Physics 2026-02-04 Hengyue Li , Yusheng Yang , Zhe-Hui Wang , Shuxin Xie , Zilong Zha , Hantao Sun , Jie Chen , Jian Sun , Shenggang Ying

In this paper we develop a quantum algorithm to realize finite temperature simulation on a quantum computer. As quantum computers use real-time evolution we did not use the imaginary time methods popular on classical algorithms. Instead, we…

Quantum Physics · Physics 2019-11-11 Raffaele Miceli , Michael McGuigan

Quantum algorithms are promising candidates for the enhancement of computational efficiency for a variety of computational tasks, allowing for the numerical study of physical systems intractable to classical computers. In the Noisy…

Quantum Physics · Physics 2021-05-13 Marco Majland , Nikolaj Thomas Zinner

We describe the contextual subspace variational quantum eigensolver (CS-VQE), a hybrid quantum-classical algorithm for approximating the ground state energy of a Hamiltonian. The approximation to the ground state energy is obtained as the…

Quantum Physics · Physics 2021-05-19 William M. Kirby , Andrew Tranter , Peter J. Love

We present a scalable framework for accurately modeling many-body interactions in surface-code quantum processor units (QPUs). Combining a concise diagrammatic formalism with high-precision numerical methods, our approach efficiently…

Quantum Physics · Physics 2025-07-09 Xuexin Xu , Kuljeet Kaur , Chloé Vignes , Mohammad H. Ansari , John M. Martinis

Combinatorial optimization is a promising application for near-term quantum computers, however, identifying performant algorithms suited to noisy quantum hardware remains as an important goal to potentially realizing quantum computational…

Quantum Physics · Physics 2025-04-01 Titus D. Morris , Ananth Kaushik , Martin Roetteler , Phillip C. Lotshaw

We present an encoding technique that reduces the effects of noise on quantum spin systems whose operation is driven by Hamiltonian evolution. This technique is widely applicable, being most relevant to the scenarios where there are…

Quantum Physics · Physics 2022-03-28 Catherine Keele , Alastair Kay

Determining properties of ground states of spin Hamiltonians remains a topic of central relevance connecting disciplines of mathematical, theoretical and applied physics. In the last few decades, ground state properties of physical systems…

Quantum Physics · Physics 2021-12-28 Jacob Biamonte

Simulating molecular systems on quantum computers requires efficient mappings from Fermionic operators to qubit operators. Traditional mappings such as Jordan-Wigner or Bravyi-Kitaev often produce high-weight Pauli terms, increasing circuit…

Quantum Physics · Physics 2025-11-13 James Brown , Tarini S Hardikar , Kenny Heitritter , Kanav Setia

The Variational Quantum Eigensolver approach to the electronic structure problem on a quantum computer involves measurement of the Hamiltonian expectation value. Formally, quantum mechanics allows one to measure all mutually commuting or…

Quantum Physics · Physics 2020-03-17 Tzu-Ching Yen , Vladyslav Verteletskyi , Artur F. Izmaylov

The variational quantum eigensolver (VQE) is one of the most appealing quantum algorithms to simulate electronic structure properties of molecules on near-term noisy intermediate-scale quantum devices. In this work, we generalize the VQE…

Quantum Physics · Physics 2022-06-09 Jie Liu , Lingyun Wan , Zhenyu Li , Jinlong Yang