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In Phys. Rev. Lett. 80, 2245 (1998) an explicit expression for entanglement of formation for any two qubit state was given. Based on this result we present an expression for the Bures measure of entanglement for two qubit states. This…

Quantum Physics · Physics 2009-10-27 Alexander Streltsov

The achievement of quantum supremacy boosted the need for a robust medium of quantum information. In this task, higher-dimensional qudits show remarkable noise tolerance and enhanced security for quantum key distribution applications.…

In this didactic article we explore the concept of quantum correlations beyond entanglement. We begin by introducing and motivating the classically correlated states and then showing how to quantify the quantum correlations using an…

Quantum Physics · Physics 2016-11-08 Gerardo Adesso , Marco Cianciaruso , Thomas R. Bromley

Discord and entanglement characterize two kinds of quantum correlations, and discord captures more correlation than entanglement in the sense that even separable states may have nonzero discord. In this paper, we propose a new kind of…

Quantum Physics · Physics 2015-06-02 Jianwei Xu

Quantum correlations between parts of a composite system most clearly reveal themselves through entanglement. Designing, maintaining, and controlling entangled systems is very demanding, which raises the stakes for understanding the…

Quantum Physics · Physics 2019-09-04 Matthew A. Hunt , Igor V. Lerner , Igor V. Yurkevich , Yuval Gefen

Quantifying entanglement in quantum systems is an important yet challenging task due to its NP-hard nature. In this work, we propose an efficient algorithm for evaluating distance-based entanglement measures. Our approach builds on…

Quantum Physics · Physics 2023-08-07 Yixuan Hu , Ye-Chao Liu , Jiangwei Shang

We discuss the problem of the separation of total correlations in a given quantum state into entanglement, dissonance, and classical correlations using the concept of relative entropy as a distance measure of correlations. This allows us to…

Quantum Physics · Physics 2010-03-03 Kavan Modi , Tomasz Paterek , Wonmin Son , Vlatko Vedral , Mark Williamson

A survey of various concepts in quantum information is given, with a main emphasis on the distinguishability of quantum states and quantum correlations. Covered topics include generalized and least square measurements, state discrimination,…

Quantum Physics · Physics 2015-06-22 Dominique Spehner

Quantum discord, a measure of quantum correlation beyond entanglement, is initially defined as the discord between two classically equivalent while quantum discordant definitions of mutual information. In this paper, we report some new…

Quantum Physics · Physics 2013-03-05 X. -J. Ren , H. Fan

Using very general arguments, we prove that any entanglement measures based on distance must be maximal on pure states. Furthermore, we show that Bures measure of entanglement and geometric measure of entanglement satisfy the monogamy…

Quantum Physics · Physics 2021-05-11 Limin Gao , Fengli Yan , Ting Gao

We investigate and compare three distinguished geometric measures of bipartite quantum correlations that have been recently introduced in the literature: the geometric discord, the measurement-induced geometric discord, and the discord of…

Quantum Physics · Physics 2016-05-26 Wojciech Roga , Dominique Spehner , Fabrizio Illuminati

Entanglement distribution with separable states has recently attracted considerable attention. Recent results suggest that quantum discord - a measure for quantum correlations beyond entanglement - is responsible for this counterintuitive…

Quantum Physics · Physics 2014-09-26 Alexander Streltsov , Hermann Kampermann , Dagmar Bruß

Two-qubit X-state is a large class of quantum states which plays an important role in the quantification and dynamical study of quantum correlations. However, the corresponding quantification of quantum discord is still missing for bona…

Quantum Physics · Physics 2021-06-23 Chunhe Xiong , Guijun Zhang

Quantum entanglement between several particles is essential for applications like quantum metrology or quantum cryptography, but it is also central for foundational phenomena like quantum non-locality. This leads to the problem of…

Quantum Physics · Physics 2025-10-10 Lisa T. Weinbrenner , Otfried Gühne

The relative entropy of entanglement $E_R$ is defined as the distance of a multi-partite quantum state from the set of separable states as measured by the quantum relative entropy. We show that this optimisation is always achieved, i.e. any…

Quantum Physics · Physics 2023-10-27 Ludovico Lami , Maksim E. Shirokov

We relate the the distinguishability of quantum states with their robustness of the entanglement, where the robustness of any resource quantifies how tolerant it is to noise. In particular, we identify upper and lower bounds on the…

Quantum Physics · Physics 2025-12-24 Debarupa Saha , Kornikar Sen , Chirag Srivastava , Ujjwal Sen

In this paper we develop an approach for detecting entanglement, which is based on measuring quantum correlations and constructing a correlation matrix. The correlation matrix is then used for defining a family of parameters, named…

Quantum Physics · Physics 2021-02-03 Bar Y. Peled , Amit Te'eni , Avishy Carmi , Eliahu Cohen

Quantum correlation often refers to correlations exhibited by two or more local subsystems under a suitable measurement. These correlations are beyond the framework of classical statistics and the associated classical probability…

Quantum Physics · Physics 2022-11-09 Biveen Shajilal , Elanor Huntington , Ping Koy Lam , Syed Assad

Originally introduced as the difference between two possible forms of quantum mutual information, quantum discord has posteriorly been shown to admit a formulation according to which it measures a distance between the state under scrutiny…

Quantum Physics · Physics 2018-10-01 P. R. Dieguez , R. M. Angelo

It is well known that for pure states the relative entropy of entanglement is equal to the reduced entropy, and the closest separable state is explicitly known as well. The same holds for Renyi relative entropy per recent results. We ask…

Quantum Physics · Physics 2021-02-10 Anna Vershynina