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Realisation of experiments even on small and medium-scale quantum computers requires an optimisation of several parameters to achieve high-fidelity operations. As the size of the quantum register increases, the characterisation of quantum…

Quantum Physics · Physics 2020-08-11 F. Martínez-García , D. Vodola , M. Müller

Estimation of physical observables for unknown quantum states is an important problem that underlies a wide range of fields, including quantum information processing, quantum physics, and quantum chemistry. In the context of quantum…

Quantum Physics · Physics 2024-05-21 Yuma Nakamura , Yoshichika Yano , Nobuyuki Yoshioka

The reduced density matrix (RDM) is crucial in quantum many-body systems for understanding physical properties, including all local physical quantity information. This study aims to minimize various error constraints that causes challenges…

Quantum Physics · Physics 2024-01-01 Nayuta Takemori , Yusuke Teranishi , Wataru Mizukami , Nobuyuki Yoshioka

Computing finite temperature properties of a quantum many-body system is key to describing a broad range of correlated quantum many-body physics from quantum chemistry and condensed matter to thermal quantum field theories. Quantum…

Quantum Physics · Physics 2023-08-16 Hai Wang , Jue Nan , Tao Zhang , Xingze Qiu , Wenlan Chen , Xiaopeng Li

In quantum mechanics, measuring the expectation value of a general observable has an inherent statistical uncertainty that is quantified by variance or mean squared error of measurement outcome. While the uncertainty can be reduced by…

Quantum Physics · Physics 2025-05-08 Kaito Wada , Naoki Yamamoto , Nobuyuki Yoshioka

The accurate estimation of quantum observables is a critical task in science. With progress on the hardware, measuring a quantum system will become increasingly demanding, particularly for variational protocols that require extensive…

A new basis adaptive algorithm for hybrid quantum-classical platforms is introduced to efficiently find the ground-state (gs) properties of quantum many-body systems. The method addresses limitations of many algorithms, such as Variational…

Strongly Correlated Electrons · Physics 2025-12-16 Anutosh Biswas , Sayan Ghosh , Ritajit Majumdar , Mostafizur Rahaman , Manoranjan Kumar

We provide fast algorithms for simulating many body Fermi systems on a universal quantum computer. Both first and second quantized descriptions are considered, and the relative computational complexities are determined in each case. In…

Quantum Physics · Physics 2009-10-30 Daniel S. Abrams , Seth Lloyd

As fully fault-tolerant quantum computers capable of solving useful problems remain a distant goal, we anticipate an era of "early fault tolerance" where limited error correction is available. We propose a framework for designing early…

Quantum phase estimation (QPE) is a promising quantum algorithm for obtaining molecular ground-state energies with chemical accuracy. However, its computational cost, dominated by the Hamiltonian 1-norm $\lambda$ and the cost of the block…

Performing large-scale, accurate quantum simulations of many-fermion systems is a central challenge in quantum science, with applications in chemistry, materials, and high-energy physics. Despite significant progress, realizing generic…

Quantum Physics · Physics 2025-09-12 Nishad Maskara , Marcin Kalinowski , Daniel Gonzalez-Cuadra , Mikhail D. Lukin

Quantum simulation using time evolution in phase estimation-based quantum algorithms can yield unbiased solutions of classically intractable models. However, long runtimes open such algorithms to decoherence. We show how measurement-based…

Quantum Physics · Physics 2022-08-11 Woo-Ram Lee , Zhangjie Qin , Robert Raussendorf , Eran Sela , V. W. Scarola

Quantum simulation of molecular electronic structure is one of the most promising applications of quantum computing. However, achieving chemically accurate predictions for strongly correlated systems requires quantum phase estimation (QPE)…

Quantum Physics · Physics 2026-03-31 Shota Kanasugi , Riki Toshio , Kazunori Maruyama , Hirotaka Oshima

The generalized eigenvalue (GE) problems are of particular importance in various areas of science engineering and machine learning. We present a variational quantum algorithm for finding the desired generalized eigenvalue of the GE problem,…

Quantum Physics · Physics 2022-03-08 Jin-Min Liang , Shu-Qian Shen , Ming Li , Shao-Ming Fei

Quantum computers are expected to accelerate solving combinatorial optimization problems, including algorithms such as Grover adaptive search and quantum approximate optimization algorithm (QAOA). However, many combinatorial optimization…

Quantum Physics · Physics 2023-05-05 Takuya Yoshioka , Keita Sasada , Yuichiro Nakano , Keisuke Fujii

The famous, yet unsolved, Fermi-Hubbard model for strongly-correlated electronic systems is a prominent target for quantum computers. However, accurately representing the Fermi-Hubbard ground state for large instances may be beyond the…

We introduce a fast and accurate heuristic for adaptive tomography that addresses many of the limitations of prior methods. Previous approaches were either too computationally intensive or tailored to handle special cases such as single…

Quantum Physics · Physics 2017-11-16 Christopher Granade , Christopher Ferrie , Steven T. Flammia

We construct a quantum Monte Carlo algorithm for interacting fermions using the two-body density as the fundamental quantity. The central idea is mapping the interacting fermionic system onto an auxiliary system of interacting bosons. The…

Statistical Mechanics · Physics 2008-07-30 Balazs Hetenyi , L. Brualla , S. Fantoni

A hybrid quantum-classical algorithm is a computational scheme in which quantum circuits are used to extract information that is then processed by a classical routine to guide subsequent quantum operations. These algorithms are especially…

Quantum Physics · Physics 2025-09-03 Alon Levi , Ziv Ossi , Eliahu Cohen , Amit Te'eni

We show in detail how the Jordan-Wigner transformation can be used to simulate any fermionic many-body Hamiltonian on a quantum computer. We develop an algorithm based on appropriate qubit gates that takes a general fermionic Hamiltonian,…

Quantum Physics · Physics 2007-05-23 E. Ovrum , M. Hjorth-Jensen