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Quantum resource theories (QRTs) provide a unified framework to analyze quantum properties as resources for achieving advantages in quantum information processing. The generalized robustness and the weight of resource have been gaining…

Quantum Physics · Physics 2024-04-24 Kohdai Kuroiwa , Ryuji Takagi , Gerardo Adesso , Hayata Yamasaki

Qubit noise spectroscopy is an important tool for the experimental investigation of open quantum systems. However, conventional techniques for noise spectroscopy are time-consuming, because they require measurements of the noise spectral…

Quantum Physics · Physics 2025-06-24 Kaixin Huang , Demitry Farfurnik , Alireza Seif , Mohammad Hafezi , Yi-Kai Liu

Quantum-enhanced multiparameter sensing is often associated with distributed architectures or 2-anticoherent states, whereas squeezing in a single collective ensemble is typically limited to single-parameter metrology. Here, we show that a…

Quantum Physics · Physics 2026-05-27 Xiaoshui Lin , Chunlei Qu , Chong Zu , Chuanwei Zhang

This paper presents a novel density estimation method for anomaly detection using density matrices (a powerful mathematical formalism from quantum mechanics) and Fourier features. The method can be seen as an efficient approximation of…

Machine Learning · Computer Science 2022-10-27 Oscar Bustos-Brinez , Joseph Gallego-Mejia , Fabio A. González

Quantum sensing explores protocols using the quantum resource of sensors to achieve highly sensitive measurement of physical quantities. The conventional schemes generally use unitary dynamics to encode quantities into sensor states. In…

Quantum Physics · Physics 2021-05-26 Wei Wu , Si-Yuan Bai , Jun-Hong An

A simple and efficient method for characterization of multidimensional Gaussian states is suggested and experimentally demonstrated. Our scheme shows analogies with tomography of finite dimensional quantum states, with the covariance matrix…

The methods of quantum chemistry and solid state theory to solve the many-body problem are reviewed. We start with the definitions of reduced density matrices, their properties (contraction sum rules, spectral resolutions, cumulant…

Strongly Correlated Electrons · Physics 2007-05-23 P. Ziesche , F. Tasnadi

Efficient range-summability (ERS) of a long list of random variables is a fundamental algorithmic problem that has applications to three important database applications, namely, data stream processing, space-efficient histogram maintenance…

Data Structures and Algorithms · Computer Science 2023-01-25 Jingfan Meng , Huayi Wang , Jun Xu , Mitsunori Ogihara

The density matrix formalism which is widely used in the theory of measurements, quantum computing, quantum description of chemical and biological systems always imply the averaging over the states of the environment. In practice this is…

Quantum Physics · Physics 2007-05-23 M. V. Altaisky

We describe a numerical algorithm for approximating the equilibrium-reduced density matrix and the effective (mean force) Hamiltonian for a set of system spins coupled strongly to a set of bath spins when the total system (system+bath) is…

Quantum Physics · Physics 2023-01-25 Tyler Chen , Yu-Chen Cheng

Referring expression counting (REC) algorithms are for more flexible and interactive counting ability across varied fine-grained text expressions. However, the requirement for fine-grained attribute understanding poses challenges for prior…

Computer Vision and Pattern Recognition · Computer Science 2025-03-18 Zhicheng Wang , Zhiyu Pan , Zhan Peng , Jian Cheng , Liwen Xiao , Wei Jiang , Zhiguo Cao

Quantum state tomography is the conventional method used to characterize density matrices for general quantum states. However, the data acquisition time generally scales linearly with the dimension of the Hilbert space, hindering the…

Quantum Physics · Physics 2021-07-28 Yiyu Zhou , Jiapeng Zhao , Darrick Hay , Kendrick McGonagle , Robert W. Boyd , Zhimin Shi

Quantum coherence is the most distinguished signature of quantum mechanics, also recognized to be an essential resource for many promising quantum technologies, playing a central role in phenomena related to quantum information science,…

Quantum Physics · Physics 2019-02-27 Bertúlio de Lima Bernardo

We discuss the concept of connection states (or connection matrices) that describe posterior ensembles, post-selected according to the outcomes of a quantum measurement. Connection matrices allow one to obtain results of any weak and some…

Quantum Physics · Physics 2013-08-02 Abraham G. Kofman , Sahin K. Ozdemir , Franco Nori

In this paper, we establish a general theoretical framework for the description of continuous quantum measurements and the statistics of the results of such measurements. The framework concerns the measurement of an arbitrary quantum system…

Quantum Physics · Physics 2018-04-23 Albert Franquet , Yuli V. Nazarov , Hongduo Wei

Quantum state tomography is a technique in quantum information science used to reconstruct the density matrix of an unknown quantum state, providing complete information about the quantum state. It is of significant importance in fields…

Quantum Physics · Physics 2025-07-23 Wenlong Zhao , Da Zhang , Huili Zhang , Haifeng Yu , Zhang-qi Yin

Accurate electronic structure calculations are essential in modern materials science, but strongly correlated systems pose a significant challenge due to their computational cost. Traditional methods, such as complete active space…

Chemical Physics · Physics 2024-12-11 Pavlo Golub , Chao Yang , Vojtěch Vlček , Libor Veis

Quantum resource theories (QRTs) provide a unified framework for characterizing useful quantum phenomena subject to physical constraints, but are notoriously hard to assess in experimental systems. In this letter, we introduce a unified…

Quantum Physics · Physics 2025-12-12 Naga Dileep Varikuti , Soumik Bandyopadhyay , Philipp Hauke

An efficient approach to calculate approximate pure-state and transition reduced density matrices in the framework of the multireference relativistic Fock-space coupled cluster (FS CC) theory is proposed. The method is based on the…

Computational Physics · Physics 2025-06-12 Alexander V. Oleynichenko , Andrei Zaitsevskii , Leonid V. Skripnikov , Ephraim Eliav

Fighting against noise is crucial for NISQ devices to demonstrate practical quantum applications. In this work, we give a new paradigm of quantum error mitigation based on the vectorization of density matrices. Different from the ideas of…

Quantum Physics · Physics 2024-07-22 Zhong-Xia Shang , Zi-Han Chen , Cai-Sheng Cheng