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This work studies pulse based variational quantum algorithms (VQAs), which are designed to determine the ground state of a quantum mechanical system by combining classical and quantum hardware. In contrast to more standard gate based…

Quantum Physics · Physics 2023-02-01 Robert de Keijzer , Oliver Tse , Servaas Kokkelmans

A family of Variational Quantum Eigensolver (VQE) methods is designed to maximize the resource of existing noisy intermediate-scale quantum (NISQ) devices. However, VQE approaches encounter various difficulties in simulating molecules of…

Chemical Physics · Physics 2022-08-16 M. D. Sapova , A. K. Fedorov

Ab initio wavefunction methods provide accurate molecular simulations but their computational scaling restricts applications to small systems. We develop a workflow combining quantum embedding to decompose a molecule into fragments with a…

Virtual distillation (VD) using measurements of multiple copies of a quantum circuit have recently been proposed as a method of noise mitigation of expectation values. Circuit decompositions known as B gates were found only for single qubit…

Quantum Physics · Physics 2024-08-29 Akib Karim , Shaobo Zhang , Muhammad Usman

Near-term hardware is constrained by high error rates, small qubit counts, and relatively low output fidelity, making the execution of large, high performance quantum circuits difficult. Circuit partitioning (or circuit cutting) has emerged…

Quantum Physics · Physics 2026-04-27 Connor Howe , Cristina Radian , Justin Woodring , Vardaan Sahgal , Brian J. McDermott

Designing compact and accurate circuits for the variational quantum eigensolver (VQE) is a central challenge in near-term quantum chemistry. Existing adaptive methods such as ADAPT-VQE design circuits by iteratively selecting operators from…

Quantum Physics · Physics 2026-05-28 Jianpeng Chen , Zirui Sheng , Cunxi Gong , Weitang Li

Quantum process tomography is often used to completely characterize an unknown quantum process. However, it may lead to an unphysical process matrix, which will cause the loss of information respect to the tomography result. Convex…

Quantum Physics · Physics 2018-09-13 Xuan-Lun Huang , Jun Gao , Zhi-Qiang Jiao , Zeng-Quan Yan , Ling Ji , Xian-Min Jin

Peephole optimization of quantum circuits provides a method of leveraging standard circuit synthesis approaches into scalable quantum circuit optimization. One application of this technique partitions an entire circuit into a series of…

Quantum Physics · Physics 2024-09-11 Joseph Clark , Himanshu Thapliyal

The Coupled Cluster (CC) method is used to compute the electronic correlation energy in atoms and molecules and often leads to highly accurate results. However, due to its single-reference nature, standard CC in its projected form fails to…

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

Objective: Despite recent advancements in quantum computing, the limited number of available qubits has hindered progress in CT reconstruction. This study investigates the feasibility of utilizing quantum annealing-based computed tomography…

Quantum Physics · Physics 2024-02-12 Akihiro Haga

Variational quantum algorithms exploit the features of superposition and entanglement to optimize a cost function efficiently by manipulating the quantum states. They are suitable for noisy intermediate-scale quantum (NISQ) computers that…

Quantum Physics · Physics 2023-08-29 Yunya Liu , Jiakun Liu , Jordan R. Raney , Pai Wang

Near-term quantum devices generally suffer from shallow circuit depth and hence limited expressivity due to noise and decoherence. To address this, we propose tensor-network-assisted parametrized quantum circuits, which concatenate a…

Quantum Physics · Physics 2023-12-01 Junxiang Huang , Wenhao He , Yukun Zhang , Yusen Wu , Bujiao Wu , Xiao Yuan

Universal compilation is a training process that compiles a trainable unitary into a target unitary and it serves vast potential applications from quantum dynamic simulations to optimal circuits with deep-compressing, device benchmarking,…

Quantum Physics · Physics 2022-04-26 Vu Tuan Hai , Le Bin Ho

Distributed quantum computing (DQC) connects many small quantum processors into a single logical machine, offering a practical route to scalable quantum computation. However, most existing DQC paradigms are structure-agnostic. Circuit…

Quantum Physics · Physics 2026-03-10 Yuwen Huang , Xiaojun Lin , Bin Luo , John C. S. Lui

Variational quantum algorithms (VQAs) are the quantum analog of classical neural networks (NNs). A VQA consists of a parameterized quantum circuit (PQC) which is composed of multiple layers of ansatzes (simpler PQCs, which are an analogy of…

Quantum Physics · Physics 2022-08-25 Afrad Basheer , Yuan Feng , Christopher Ferrie , Sanjiang Li

Accelerating quantum dynamical simulations with quantum computing has received considerable attention but remains a significant challenge. In variational quantum algorithms for quantum dynamics, designing an expressive and shallow-depth…

Chemical Physics · Physics 2025-06-10 Jingjing Li , Weitang Li , Xiaoxiao Xiao , Limin Liu , Zhendong Li , Jiajun Ren , Weihai Fang

Quantum state tomography provides a fundamental framework for reconstructing quantum states. When the measurement data are not informationally complete, the observed statistics admit multiple compatible density matrices, making the…

Quantum Physics · Physics 2026-05-01 V. A. Penas , M. Losada , D. Tielas , F. Holik

Drawing inspiration from gradient-descent methods developed for data processing in quantum state tomography [\href{https://iopscience.iop.org/article/10.1088/2058-9565/ae0baa}{Quantum Sci.~Technol.~\textbf{10} 045055 (2025)}] and quantum…

Quantum Physics · Physics 2026-02-05 Akshay Gaikwad , Manuel Sebastian Torres , Anton Frisk Kockum

Despite advances in the development of quantum computers, the practical application of quantum algorithms requiring deep circuit depths or high-fidelity transformations remains outside the current range of the so-called noisy…