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Quantum imaginary time evolution (QITE) algorithm is one of the most promising variational quantum algorithms (VQAs), bridging the current era of Noisy Intermediate-Scale Quantum devices and the future of fully fault-tolerant quantum…

Quantum Physics · Physics 2025-10-28 Min Chen , Bingzhi Zhang , Quntao Zhuang , Junyu Liu

Simulating the time evolution of quantum field theories given some Hamiltonian $H$ requires developing algorithms for implementing the unitary operator e^{-iHt}. A variety of techniques exist that accomplish this task, with the most common…

We introduce the framework of model space into quantum imaginary time evolution (QITE) to enable stable estimation of ground and excited states using a quantum computer. Model-space QITE (MSQITE) propagates a model space to the exact one by…

Quantum Physics · Physics 2023-10-02 Takashi Tsuchimochi , Yoohee Ryo , Siu Chung Tsang , Seiichiro L. Ten-no

We propose an algorithm inspired by optical coherent Ising machines to solve the problem of polynomial unconstrained binary optimization (PUBO). We benchmark the proposed algorithm against existing PUBO algorithms on the extended…

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

Numerous methodologies have been proposed to implement imaginary time evolution (ITE) on quantum computers. Among these, variational ITE (VITE) methods for noisy intermediate-scale quantum (NISQ) computers have attracted much attention,…

Quantum Physics · Physics 2025-11-26 Hiroki Kuji , Tetsuro Nikuni , Yuta Shingu

In the era of quantum computing, the emergence of quantum computers and subsequent advancements have led to the development of various quantum algorithms capable of solving linear equations and eigenvalues, surpassing the pace of classical…

Quantum Physics · Physics 2024-11-26 Hyunju Lee , Kyungtaek Jun

We introduce a constructive method for mapping non-unitary dynamics to a weighted set of unitary operations. We utilize this construction to derive a new correspondence between real and imaginary time, which we term Imaginary Time Quantum…

Quantum Physics · Physics 2024-09-11 Jacob M. Leamer , Alicia B. Magann , Denys I. Bondar , Gerard McCaul

We introduce an imaginary-time evolution method to evaluate the pure-state constrained-search functional from density-functional theory formulated on finite lattices. Simultaneously, it yields a potential that produces a prescribed density…

Materials Science · Physics 2025-09-29 Markus Penz , Robert van Leeuwen

We calculate the energy levels and corresponding eigenstates of an interacting scalar quantum field theory on a lattice using a continuous-variable version of the quantum imaginary time evolution algorithm. Only a single qumode is needed…

Quantum Physics · Physics 2022-01-19 Kübra Yeter-Aydeniz , Eleftherios Moschandreou , George Siopsis

Quantum simulations of many-body systems offer novel methods for probing the dynamics of the Standard Model and its constituent gauge theories. Extracting low-energy predictions from such simulations rely on formulating…

Quantum Physics · Physics 2025-12-30 Henry Froland , Dorota M. Grabowska , Zhiyao Li

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

We present a norm-stabilized imaginary-time evolution (ITE) scheme for the one-dimensional nonlinear Schrodinger equation (NLSE). Traditional ITE solvers often require explicit renormalization of the wavefunction after each step to preserve…

Numerical Analysis · Mathematics 2025-07-17 Stylianos Savva

We develop a resource efficient step-merged quantum imaginary time evolution approach (smQITE) to solve for the ground state of a Hamiltonian on quantum computers. This heuristic method features a fixed shallow quantum circuit depth along…

Computational Physics · Physics 2020-09-21 Niladri Gomes , Feng Zhang , Noah F. Berthusen , Cai-Zhuang Wang , Kai-Ming Ho , Peter P. Orth , Yongxin Yao

The variational quantum imaginary time evolution (VarQITE) algorithm is a near-term method to prepare the ground state and Gibbs state of Hamiltonians. Finding an appropriate parameterization of the quantum circuit is crucial to the success…

Quantum Physics · Physics 2023-07-26 Xiaoyang Wang , Yahui Chai , Maria Demidik , Xu Feng , Karl Jansen , Cenk Tüysüz

Efficiently preparing approximate ground-states of large, strongly correlated systems on quantum hardware is challenging and yet nature is innately adept at this. This has motivated the study of thermodynamically inspired approaches to…

The Schrodinger equation describes how quantum states evolve according to the Hamiltonian of the system. For physical systems, we have it that the Hamiltonian must be a Hermitian operator to ensure unitary dynamics. For anti-Hermitian…

Quantum Physics · Physics 2025-05-21 Swagat Kumar , Colin Michael Wilmott

We propose a concise function representation based on deterministic finite state automata for exact most probable explanation and constrained optimization tasks in graphical models. We then exploit our concise representation within Bucket…

Artificial Intelligence · Computer Science 2023-05-11 Filippo Bistaffa

Qubit-efficient optimization studies how large combinatorial problems can be addressed with quantum circuits whose width is far smaller than the number of logical variables. In quadratic unconstrained binary optimization (QUBO), objective…

Quantum Physics · Physics 2026-01-13 Gordon Ma , Dimitris G. Angelakis

Quadratic Unconstrained Binary Optimization (QUBO or UBQP) is concerned with maximizing/minimizing the quadratic form $H(J, \eta) = W \sum_{i,j} J_{i,j} \eta_{i} \eta_{j}$ with $J$ a matrix of coefficients, $\eta \in \{0, 1\}^N$ and $W$ a…

Probability · Mathematics 2024-07-02 Marco Isopi , Benedetto Scoppola , Alessio Troiani