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Variational quantum algorithms (VQAs) are prominent candidates for near-term quantum advantage but lack rigorous guarantees of convergence and generalization. By contrast, quantum phase estimation (QPE) provides provable performance under…

Quantum Physics · Physics 2025-10-09 Tuyen Nguyen , Mária Kieferová

Parameterized quantum circuits play a key role for the development of quantum variational algorithms in the realm of the NISQ era. Knowing their actual capability of performing different kinds of tasks is then of the utmost importance. By…

Quantum Physics · Physics 2024-05-31 Guilherme Ilário Correr , Pedro C. Azado , Diogo O. Soares-Pinto , Gabriel Carlo

Preparing the Gibbs state of an interacting quantum many-body system on noisy intermediate-scale quantum (NISQ) devices is a crucial task for exploring the thermodynamic properties in the quantum regime. It encompasses understanding…

Quantum Physics · Physics 2025-01-08 Mirko Consiglio

Quantum optimization algorithms offer a promising route to finding the ground states of target Hamiltonians on near-term quantum devices. None the less, it remains necessary to limit the evolution time and circuit depth as much as possible,…

Quantum Physics · Physics 2022-11-01 Chenfeng Cao , Yunlong Yu , Zipeng Wu , Nic Shannon , Bei Zeng , Robert Joynt

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

Imaginary time evolution is a powerful tool applied in quantum physics, while existing classical algorithms for simulating imaginary time evolution suffer high computational complexity as the quantum systems become larger and more complex.…

Quantum Physics · Physics 2022-10-12 Hao-Nan Xie , Shi-Jie Wei , Fan Yang , Zheng-An Wang , Chi-Tong Chen , Heng Fan , Gui-Lu Long

A local and distributive algorithm is proposed to find an optimal trial wave-function minimizing the Hamiltonian expectation in a quantum system. To this end, the quantum state of the system is connected to the Gibbs state of a classical…

Quantum Physics · Physics 2015-06-03 A. Ramezanpour

Quantum computers have been widely speculated to offer significant advantages in obtaining the ground state of difficult Hamiltonian in chemistry and physics. In this work, we first propose a Lyapunov control-inspired strategy to accelerate…

Quantum Physics · Physics 2022-12-21 Yu-Cheng Chen , Yu-Qin Chen , Alice Hu , Chang-Yu Hsieh , Shengyu Zhang

We propose a method for constructing $\texttt{PREPARE}$ circuits for quantum phase estimation of a molecular Hamiltonian in quantum chemistry by using variational optimization of quantum circuits solely on classical computers. The…

Quantum Physics · Physics 2025-05-02 Hayata Morisaki , Kosuke Mitarai , Keisuke Fujii , Yuya O. Nakagawa

The quantum imaginary time evolution (QITE) methodology was developed to overcome a critical issue as regards non-unitarity in the implementation of imaginary time evolution on a quantum computer. QITE has since been used to approximate…

Quantum Physics · Physics 2024-09-20 Swagat Kumar , Colin Michael Wilmott

Efficient low-energy state preparation is a key objective in quantum computation and quantum simulation. Quantum imaginary-time evolution replaces real-time dynamics with imaginary-time dynamics, exponentially suppressing higher-energy…

Quantum Physics · Physics 2026-03-13 Tal Schwartzman , Torsten V. Zache , Hannes Pichler , H. R. Sadeghpour

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

The imaginary-time evolution of quantum states is integral to various fields, ranging from natural sciences to classical optimization or machine learning. Since simulating quantum imaginary-time evolution generally requires storing an…

Quantum Physics · Physics 2024-01-17 Julien Gacon , Christa Zoufal , Giuseppe Carleo , Stefan Woerner

Imaginary-time evolution (ITE) on a quantum computer is a promising formalism for obtaining the ground state of a quantum system. As a kind of it, the probabilistic ITE (PITE) takes advantage of measurements to implement the nonunitary…

Quantum Physics · Physics 2022-08-15 Taichi Kosugi , Yusuke Nishiya , Hirofumi Nishi , Yu-ichiro Matsushita

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

The variational quantum-classical algorithms are the most promising approach for achieving quantum advantage on near-term quantum simulators. Among these methods, the variational quantum eigensolver has attracted a lot of attention in…

Quantum Physics · Physics 2023-01-24 Chufan Lyu , Xusheng Xu , Man-Hong Yung , Abolfazl Bayat

A probabilistic imaginary-time evolution (PITE) method was proposed as a nonvariational method to obtain a ground state on a quantum computer. In this formalism, the success probability of obtaining all imaginary-time evolution operators…

Quantum Physics · Physics 2022-12-29 Hirofumi Nishi , Taichi Kosugi , Yusuke Nishiya , Yu-ichiro Matsushita

The simulation of quantum dynamics calls for quantum algorithms working in first quantized grid encodings. Here, we propose a variational quantum algorithm for performing quantum dynamics in first quantization. In addition to the usual…

We propose an extended version of the symmetry-adapted variational-quantum-eigensolver (VQE) and apply it to a two-component Fermi-Hubbard model on a bipartite lattice. In the extended symmetry-adapted VQE method, the Rayleigh quotient for…

Quantum Physics · Physics 2022-03-11 Kazuhiro Seki , Seiji Yunoki

One of the key applications for the emerging quantum simulators is to emulate the ground state of many-body systems, as it is of great interest in various fields from condensed matter physics to material science. Traditionally, in an analog…

Quantum Physics · Physics 2020-09-18 Chufan Lyu , Victor Montenegro , Abolfazl Bayat