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We introduce a general framework called neural network (NN) encoded variational quantum algorithms (VQAs), or NN-VQA for short, to address the challenges of implementing VQAs on noisy intermediate-scale quantum (NISQ) computers.…

Quantum Physics · Physics 2024-02-06 Jiaqi Miao , Chang-Yu Hsieh , Shi-Xin Zhang

In a recent work [10], Poulin and one of us presented a quantum algorithm for preparing thermal Gibbs states of interacting quantum systems. This algorithm is based on Grovers's technique for quantum state engineering, and its running time…

Computational Physics · Physics 2013-06-12 Chen-Fu Chiang , Pawel Wocjan

We propose a hybrid variational quantum algorithm that has variational parameters used by both the quantum circuit and the subsequent classical optimization. Similar to the Variational Quantum Eigensolver (VQE), this algorithm applies a…

Quantum Physics · Physics 2025-12-05 John P. T. Stenger , C. Stephen Hellberg , Daniel Gunlycke

We introduce a variational approach for preparing low energy states of arbitrary target Hamiltonians. The protocol is defined in terms of a repeated cycle consisting of p layers of unitary gates applied to the system and ancilla "bath"…

Quantum Physics · Physics 2025-10-14 Jeffrey Z. Song , Gilad Kishony , Erez Berg , Mark S. Rudner

While recent advances have established efficient quantum algorithms for preparing Gibbs states of finite-dimensional systems, comparable complexity results for bosonic and other infinite-dimensional models remain unexplored. We introduce…

Quantum Physics · Physics 2026-04-08 Simon Becker , Cambyse Rouzé , Robert Salzmann

Quantum variational algorithms (QVAs) are increasingly potent tools for simulating quantum many-body systems on noisy intermediate-scale quantum (NISQ) devices. This work examines the application of the Variational Quantum Eigensolver (VQE)…

Nuclear Theory · Physics 2026-01-28 Dhritimalya Roy , Somnath Nag

Nature is governed by precise physical laws, which can inspire the discovery of new computer-run simulation algorithms. Thermal states are the most ubiquitous for they are the equilibrium states of matter. Simulating thermal states of…

Quantum Physics · Physics 2023-04-13 Oles Shtanko , Ramis Movassagh

Noisy Intermediate-Scale Quantum (NISQ) algorithms require novel paradigms of error mitigation. To obtain noise-robust quantum computers, each logical qubit is equipped with hundreds or thousands of physical qubits. However, it is not…

The Variational Quantum Eigensolver (VQE) is a hybrid quantum-classical algorithm for preparing ground states in the current era of noisy devices. The classical component of the algorithm requires a large number of measurements on…

Quantum Physics · Physics 2025-03-27 Akib Karim , Shaobo Zhang , Muhammad Usman

Preparing the ground state of a Hamiltonian is a problem of great significance in physics with deep implications in the field of combinatorial optimization. The adiabatic algorithm is known to return the ground state for sufficiently long…

Quantum Physics · Physics 2023-08-02 Benjamin F. Schiffer , Jordi Tura , J. Ignacio Cirac

Reliable preparation of many-body ground states is an essential task in quantum computing, with applications spanning areas from chemistry and materials modeling to quantum optimization and benchmarking. A variety of approaches have been…

Quantum Physics · Physics 2026-02-09 Ricard Puig , Berta Casas , Alba Cervera-Lierta , Zoë Holmes , Adrián Pérez-Salinas

Variational quantum algorithms (VQAs) are promising hybrid quantum-classical methods designed to leverage the computational advantages of quantum computing while mitigating the limitations of current noisy intermediate-scale quantum (NISQ)…

Computational Engineering, Finance, and Science · Computer Science 2025-04-18 Saibal De , Oliver Knitter , Rohan Kodati , Paramsothy Jayakumar , James Stokes , Shravan Veerapaneni

The rapid development of noisy intermediate-scale quantum (NISQ) devices has raised the question of whether or not these devices will find commercial use. Unfortunately, a major shortcoming of many proposed NISQ-amenable algorithms, such as…

Quantum Physics · Physics 2021-10-22 Amara Katabarwa , Alex Kunitsa , Borja Peropadre , Peter Johnson

Variational quantum eigensolver (VQE), aiming at determining the ground state energy of a quantum system described by a Hamiltonian on noisy intermediate scale quantum (NISQ) devices, is among the most significant applications of…

Quantum Physics · Physics 2024-04-12 Ze-Tong Li , Fan-Xu Meng , Han Zeng , Zai-Chen Zhang , Xu-Tao Yu

The realization of quantum advantage with noisy-intermediate-scale quantum (NISQ) machines has become one of the major challenges in computational sciences. Maintaining coherence of a physical system with more than ten qubits is a critical…

We investigate optimized quantum state preparation for quantum metrology applications in noisy environments. Using the QFI-Opt package, we simulate a low-depth variational quantum circuit (VQC) composed of a sequence of global rotations and…

We propose a variational quantum algorithm to prepare ground states of 1D lattice quantum Hamiltonians specifically tailored for programmable quantum devices where interactions among qubits are mediated by Quantum Data Buses (QDB). For…

Quantum Physics · Physics 2020-07-07 Viacheslav V. Kuzmin , Pietro Silvi

Variational quantum algorithms (VQAs) face an inherent trade-off between expressivity and trainability: deeper circuits can represent richer states but suffer from noise accumulation and barren plateaus, while shallow circuits remain…

Quantum Physics · Physics 2025-10-31 Shaojun Wu , Shan Jin , Abolfazl Bayat , Xiaoting Wang

Variational quantum algorithms (VQAs) represent a promising pathway toward achieving practical quantum advantage on near-term hardware. Despite this promise, for generic, expressive ans\"atze, their scalability is critically hindered by…

Quantum Physics · Physics 2026-02-26 Chenfeng Cao , Yeqing Zhou , Swamit Tannu , Nic Shannon , Robert Joynt

A spin-1 system can exhibit an intermediate-temperature topological regime with a quantized Uhlmann phase sandwiched by topologically trivial low- and high-temperature regimes. We present a quantum circuit consisting of system and ancilla…

Quantum Physics · Physics 2025-08-06 Christopher Mastandrea , Costin Iancu , Hao Guo , Chih-Chun Chien