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Many applications of quantum simulation require to prepare and then characterize quantum states by performing an efficient partial tomography to estimate observables corresponding to $k$-body reduced density matrices ($k$-RDMs). For…

Quantum Physics · Physics 2020-09-24 Xavier Bonet-Monroig , Ryan Babbush , Thomas E. O'Brien

Quantum state tomography is a fundamental task in quantum information science, enabling detailed characterization of correlations, entanglement, and electronic structure in quantum systems. However, its exponential measurement and…

Shadow tomography via classical shadows is a state-of-the-art approach for estimating properties of a quantum state. We present a simplified, combinatorial analysis of a recently proposed instantiation of this approach based on the ensemble…

Quantum Physics · Physics 2022-08-01 Bryan O'Gorman

Classical shadow tomography provides a randomized scheme for approximating the quantum state and its properties at reduced computational cost with applications in quantum computing. In this Letter we present an algorithm for realizing fewer…

Quantum Physics · Physics 2023-12-20 Irma Avdic , David A. Mazziotti

Learning quantum state properties is both a fundamental and practical problem in quantum information theory. Classical shadows have emerged as an efficient method for estimating properties of unknown quantum states, with rigorous…

Quantum Physics · Physics 2026-03-30 Hugo Thomas , Ulysse Chabaud , Pierre-Emmanuel Emeriau

Quantum shadow tomography based on the classical shadow representation provides an efficient way to estimate properties of an unknown quantum state without performing a full quantum state tomography. In scenarios where estimating the…

Quantum Physics · Physics 2026-03-13 Aniket Sengupta , Arijit Chatterjee , G. J. Sreejith , T. S. Mahesh

Many quantum algorithms, including recently proposed hybrid classical/quantum algorithms, make use of restricted tomography of the quantum state that measures the reduced density matrices, or marginals, of the full state. The most…

Quantum Physics · Physics 2018-05-16 Nicholas C. Rubin , Ryan Babbush , Jarrod McClean

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

Fermionic reduced density matrices summarize the key observables in fermionic systems. In electronic systems, the two-particle reduced density matrix (2-RDM) is sufficient to determine the energy and most physical observables of interest.…

Quantum Physics · Physics 2023-06-12 Linqing Peng , Xing Zhang , Garnet Kin-Lic Chan

We consider classical shadows of fermion wavefunctions with $\eta$ particles occupying $n$ modes. We prove that all $k$-Reduced Density Matrices (RDMs) may be simultaneously estimated to an average variance of $\epsilon^{2}$ using at most…

Quantum Physics · Physics 2024-07-26 Guang Hao Low

Dynamical correlation functions are essential for characterizing the response of the quantum many-body systems to the external perturbation. As their calculation is classically intractible in general, quantum algorithms are promising in…

Quantum Physics · Physics 2026-03-17 Taehee Ko , Mancheon Han , Hyowon Park , Sangkook Choi

Classical shadow tomography serves as a potent tool for extracting numerous properties from quantum many-body systems with minimal measurements. Nevertheless, prevailing methods yielding optimal performance for few-body operators…

Quantum Physics · Physics 2024-09-11 Tian-Gang Zhou , Pengfei Zhang

Shadow tomography is a framework for constructing succinct descriptions of quantum states using randomized measurement bases, called classical shadows, with powerful methods to bound the estimators used. We recast existing experimental…

Classical shadow tomography has become a powerful tool in learning about quantum states prepared on a quantum computer. Recent works have used classical shadows to variationally enforce N-representability conditions on the 2-particle…

Classical shadow tomography offers a scalable route to estimating properties of quantum states, but the resulting reduced density matrices (RDMs) often violate constraints that ensure they represent $N$-electron states -- known as…

We present a new method which uses Feynman-like diagrams to calculate the statistical quantities of embedded many-body random matrix problems. The method provides a promising alternative to existing techniques and offers many important…

Statistical Mechanics · Physics 2014-08-06 Rupert Small , Sebastian Müller

We present a protocol that allows the estimation of any density matrix element for continuous-variable quantum states, without resorting to the complete reconstruction of the full density matrix. The algorithm adaptatively discretizes the…

Quantum Physics · Physics 2024-09-25 Virginia Feldman , Ariel Bendersky

Achieving quantum advantage in efficiently estimating collective properties of quantum many-body systems remains a fundamental goal in quantum computing. While the quantum gradient estimation (QGE) algorithm has been shown to achieve doubly…

Quantum Physics · Physics 2025-05-05 Yuki Koizumi , Kaito Wada , Wataru Mizukami , Nobuyuki Yoshioka

Fermionic Hamiltonians play a critical role in quantum chemistry, one of the most promising use cases for near-term quantum computers. However, since encoding nonlocal fermionic statistics using conventional qubits results in significant…

Quantum Physics · Physics 2025-06-25 Irakli Giorgadze , Haixuan Huang , Jordan Gaines , Elio J. König , Jukka I. Väyrynen

Predicting properties of complex, large-scale quantum systems is essential for developing quantum technologies. We present an efficient method for constructing an approximate classical description of a quantum state using very few…

Quantum Physics · Physics 2021-04-20 Hsin-Yuan Huang , Richard Kueng , John Preskill
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