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The imaginary unit $i$ has recently been experimentally proven to be indispensable for quantum mechanics. We study the differences in detection power between real and complex entanglement witnesses (EWs) distinguished by whether their…

Quantum Physics · Physics 2025-08-01 Yi Shen , Lin Chen , Zhihao Bian

Entanglement witnesses (EWs) are a fundamental tool for the detection of entanglement. We investigate the inertias of bipartite EWs constructed by the partial transpose of NPT states. Furthermore, we find out most of the inertias of the…

Quantum Physics · Physics 2022-04-21 Changchun Feng , Lin Chen , Chang Xu , Yi Shen

The Gell-Mann $\lambda$ matrices for Lie algebra su(3) are the natural basis for the Hilbert space of Hermitian operators acting on the states of a three-level system(qutrit). So the construction of EWs for two-qutrit states by using these…

Quantum Physics · Physics 2009-11-13 M. A. Jafarizadeh , Y. Akbari , N. Behzadi

The study of Entanglement of Formation of a mixed state of a bipartite system in high-dimensional Hilbert space is not easy in general. So, we focus on determining the amount of entanglement for a bipartite mixed state based on the concept…

Quantum Physics · Physics 2009-11-13 M. A. Jafarizadeh , M. Mahdian

Entanglement detection is one of the important problems in quantum information theory. To deal with this problem, many entanglement detection criteria have been proposed. Among the proposed criteria, the detection of entanglement through…

Quantum Physics · Physics 2026-05-06 Sonia , Satyabrata Adhikari

Entanglement, a critical resource for quantum information processing, needs to be witnessed in many practical scenarios. Theoretically, witnessing entanglement is by measuring a special Hermitian observable, called entanglement witness…

Quantum Physics · Physics 2016-04-20 Xiao Yuan , Quanxin Mei , Shan Zhou , Xiongfeng Ma

Entanglement witnesses are invaluable for efficient quantum entanglement certification without the need for expensive quantum state tomography. Yet, standard entanglement witnessing requires multiple measurements and its bounds can be…

Quantum Physics · Physics 2017-03-22 Farid Shahandeh , Martin Ringbauer , Juan C. Loredo , Timothy C. Ralph

Genuine multipartite entanglement is arguably the most valuable form of entanglement in the multipartite case, with applications, for instance, in quantum metrology. In order to detect that form of entanglement in multipartite quantum…

Quantum Physics · Physics 2026-04-07 Jakub Szczepaniak , Owidiusz Makuta , Remigiusz Augusiak

We show how to detect entangled, bound entangled, and separable bipartite quantum states of arbitrary dimension and mixedness using geometric entanglement witnesses. These witnesses are constructed using properties of the Hilbert-Schmidt…

Quantum Physics · Physics 2009-11-13 Philipp Krammer

It has been shown that finding generic Bell states diagonal entanglement witnesses (BDEW) for $d_{1}\otimes d_{2}\otimes ....\otimes d_{n}$ systems exactly reduces to a linear programming if the feasible region be a polygon by itself and…

Quantum Physics · Physics 2009-11-11 M. A. Jafarizadeh , M. Rezaee , S. K. A. Seyed Yagoobi

We consider entanglement witnesses arising from positive linear maps which generate exposed extremal rays. We show that every entanglement can be detected by one of these witnesses, and this witness detects a unique set of entanglement…

Quantum Physics · Physics 2012-01-10 Kil-Chan Ha , Seung-Hyeok Kye

In this paper we present a new method for entanglement witnesses construction. We show that to construct such an object we can deal with maps which are not positive on the whole domain, but only on a certain sub-domain. In our approach…

Quantum Physics · Physics 2015-09-25 Marek Mozrzymas , Adam Rutkowski , Michał Studziński

Entanglement witnesses (EWs) are a collection of observables that can characterize separable states and, experimentally, estimating EWs can verify entangled states. In this work, we show that a fixed measurement setting on a multipartite…

Quantum Physics · Physics 2026-05-29 Jaemin Kim , Anindita Bera , Dariusz Chruściński , Joonwoo Bae

Recently, a toolkit of highly symmetric techniques employing matrix inequalities has been developed to detect entanglement in various ways. Here we unifiedly explain in detail these methods, and expand them to a new family of positive maps…

Quantum Physics · Physics 2026-02-10 Albert Rico

Entanglement is a central concept in quantum information and a key resource for many quantum protocols. In this work we propose and analyze a class of entanglement witnesses that detect the presence of entanglement in subsystems of…

Quantum Physics · Physics 2020-01-22 David Amaro , Markus Müller

Motivated by the Peres-Horodecki criterion and the realignment criterion we develop a more powerful method to identify entangled states for any bipartite system through a universal construction of the witness operator. The method also gives…

Quantum Physics · Physics 2009-11-10 Kai Chen , Ling-An Wu

Entanglement witnesses (EW) allow the detection of entanglement in a quantum system, from the measurement of some few observables. They do not require the complete determination of the quantum state, which is regarded as a main advantage.…

Quantum Physics · Physics 2012-02-02 J. G. Filgueiras , T. O. Maciel , R. E. Auccaise , R. O. Vianna , R. S. Sarthour , I. S. Oliveira

From the physical point of view entanglement witnesses define a universal tool for analysis and classification of quantum entangled states. From the mathematical point of view they provide highly nontrivial generalization of positive…

Quantum Physics · Physics 2014-12-30 Dariusz Chruściński , Gniewomir Sarbicki

We characterize a convex subset of entanglement witnesses for two qutrits. Equivalently, we provide a characterization of the set of positive maps in the matrix algebra of 3 x 3 complex matrices. It turns out that boundary of this set…

Quantum Physics · Physics 2012-01-31 Dariusz Chruściński , Filip A. Wudarski

We study entanglement witnesses that can be constructed with regard to the geometrical structure of the Hilbert-Schmidt space, i.e. we present how to use these witnesses in the context of quantifying entanglement and the detection of bound…

Quantum Physics · Physics 2009-11-13 Reinhold A. Bertlmann , Philipp Krammer