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Quantum systems in excited states are attracting significant interest with the advent of noisy intermediate scale quantum (NISQ) devices. While ground states of small molecular systems are typically explored using hybrid variational…

Quantum Physics · Physics 2025-11-18 Cameron Cianci , Lea F. Santos , Victor S. Batista

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 plays an important role in algorithms for computing ground-state and thermal equilibrium properties of quantum systems, but can be challenging to simulate on classical computers. Many quantum algorithms for…

Quantum Physics · Physics 2025-07-22 Annie Ray , Esha Swaroop , Ningping Cao , Michael Vasmer , Anirban Chowdhury

Despite remarkable successes in solving various complex decision-making tasks, training an imitation learning (IL) algorithm with deep neural networks (DNNs) suffers from the high computation burden. In this work, we propose quantum…

Quantum Physics · Physics 2023-04-06 Zhihao Cheng , Kaining Zhang , Li Shen , Dacheng Tao

Machine learning is widely believed to be one of the most promising practical applications of quantum computing. Existing quantum machine learning schemes typically employ a quantum-classical hybrid approach that relies crucially on…

Quantum Physics · Physics 2025-02-11 Qi Ye , Shuangyue Geng , Zizhao Han , Weikang Li , L. -M. Duan , Dong-Ling Deng

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

This paper introduces Witnessed Quantum Time Evolution (WQTE), a novel quantum algorithm for efficiently computing the eigen-energy spectra of arbitrary quantum systems without requiring eigenstate preparation-a key limitation of…

Quantum Physics · Physics 2026-03-19 Qing-Xing Xie , Zidong Lin , Yun-Long Liu , Yan Zhao

Quantum information science and engineering (QISE) is a rapidly developing field that leverages the skills of experts from many disciplines to utilize the potential of quantum systems in a variety of applications. It requires talent from a…

Physics Education · Physics 2024-08-12 Peter Hu , Yangqiuting Li , Chandralekha Singh

An adaptive variational quantum imaginary time evolution (AVQITE) approach is introduced that yields efficient representations of ground states for interacting Hamiltonians on near-term quantum computers. It is based on McLachlan's…

Variational quantum algorithms (VQAs) have established themselves as a central computational paradigm in the Noisy Intermediate-Scale Quantum (NISQ) era. By coupling parameterized quantum circuits (PQCs) with classical optimization, they…

The quantum imaginary time evolution is a powerful algorithm for preparing the ground and thermal states on near-term quantum devices. However, algorithmic errors induced by Trotterization and local approximation severely hinder its…

Quantum Physics · Physics 2022-03-16 Chenfeng Cao , Zheng An , Shi-Yao Hou , D. L. Zhou , Bei Zeng

Many current and near-future applications of quantum computing utilise parametric families of quantum circuits and variational methods to find optimal values for these parameters. Solving a quantum computational problem with such…

Quantum Physics · Physics 2025-08-05 Tobias Hartung , Karl Jansen

We study the Schwinger model at finite-temperature regime using a quantum-classical hybrid algorithm. The preparation of thermal state on quantum circuit presents significant challenges. To address this, we adopt the Thermal Pure Quantum…

High Energy Physics - Lattice · Physics 2023-11-21 Juan W. Pedersen , Etsuko Itou , Rong-Yang Sun , Seiji Yunoki

Quantum natural gradient has emerged as a superior minimisation technique in quantum variational algorithms. Classically simulating the algorithm running on near-future quantum hardware is paramount in its study, as it is for all…

Quantum Physics · Physics 2020-11-06 Tyson Jones

The variational quantum eigensolver (VQE) is an algorithm for finding the ground states of a given Hamiltonian. Its application to binary-formulated combinatorial optimization (CO) has been widely studied in recent years. However, typical…

Quantum Physics · Physics 2025-08-08 Ningyi Xie , Xinwei Lee , Tiejin Chen , Yoshiyuki Saito , Nobuyoshi Asai , Dongsheng Cai

The Variational Quantum Eigensolver (VQE) is one of the most promising algorithms for current quantum devices. It employs a classical optimizer to iteratively update the parameters of a variational quantum circuit in order to search for the…

Quantum Physics · Physics 2025-11-19 Chenyu Shi , Hao Wang

We introduce a unified framework -- Quantum Neural Ordinary and Partial Differential Equations (QNODEs and QNPDEs) -- which extends the continuous-time formalism of classical neural ordinary and partial differential equations into quantum…

Quantum Physics · Physics 2026-01-13 Yu Cao , Shi Jin , Nana Liu

Various methods have been developed for the quantum computation of the ground and excited states of physical and chemical systems, but many of them require either large numbers of ancilla qubits or high-dimensional optimization. The quantum…

Quantum Physics · Physics 2019-12-16 Kübra Yeter-Aydeniz , Raphael C. Pooser , George Siopsis

Extracting energy spectra from quantum Hamiltonians is a fundamental task for quantum simulation, yet remains challenging on noisy intermediate-scale quantum (NISQ) devices. We propose Measured Quantum Time Evolution (MQTE), an ancilla-free…

Quantum Physics · Physics 2026-03-19 Qing-Xing Xie , Yong-Kang Duan , Fa-Hui Liu , Yan Zhao

A quantum generalization of Natural Gradient Descent is presented as part of a general-purpose optimization framework for variational quantum circuits. The optimization dynamics is interpreted as moving in the steepest descent direction…

Quantum Physics · Physics 2020-05-27 James Stokes , Josh Izaac , Nathan Killoran , Giuseppe Carleo